PUBLIC HEALTH ASSESSMENT
FORT WAINWRIGHT, FAIRBANKS NORTH STAR BOROUGH, ALASKA
Permafrost and Contaminant Transport at Fort Wainwright
Permafrost is defined as ground (rock or soil) whose temperature stays below 0º C for 2 or more years. Its occurrence is influenced by terrain factors (relief, or vertical variation between the high and low elevations of an area; slope aspect, or the steepness and direction of the slope face; vegetation; snow cover; moisture content; and soil and rock type) and the presence of surface water bodies (Sloan and van Everdingen 1988; USGS 1999).
Permafrost is defined solely on the basis of its temperature; it is not necessarily a frozen-solid block. It can be dry (containing no water or ice) or contain waterfrozen or unfrozen, or both. Segregated ice in permafrost can exist as lenses, layers, or ice wedges. Typically, any unfrozen water that remains in a permafrost region has a lower-than-normal freezing point (e.g., because it contains dissolved minerals) and increased viscosity. Thin films of water exist in many soil-water-ice systems, adsorbed on mineral surfaces. The adsorbed water is mobile and responds to both electrical and thermal gradients (Sloan and van Everdingen 1988).
The major components of permafrost are the:
- Active layer: the zone that lies above the permafrost. The active layer freezes in the winter and thaws in the summer (USGS 1999).
- Permafrost: rock or soil with a temperature of less than 0º C continuously for two or more years.
- Permafrost table: the upper surface of the permafrost (USGS 1999).
- Talik: an unfrozen zone within the permafrost (Lawson et al. 1998).
Permafrost at Fort Wainwright
Fairbanks is in the region of discontinuous permafrost. The depth to the permafrost table variesbetween 0.5 to 20 meters below the ground surface, while the base is commonly 10 to 50 metersbelow the ground surface (Ferrians 1965; Williams 1970).
"Discontinuous permafrost" refers to a region where some areas are underlain by permafrost andneighboring areas are not perennially frozen. The unfrozen zones can be isolated or interconnected(USGS 1999). In northern Alaska, essentially all areas unaffected by human activity are underlainby permafrost. Moving southward, the percentage of unfrozen acreage increases, so that areas nearthe southern and southeastern coastal regions of Alaska contain essentially no permafrost (USGS1999).
Changes from frozen to unfrozen conditions can occur abruptly across an area and might not benoticeable from the ground surface (Lawson et al. 1998).
Groundwater in Permafrost
There are three major types of aquifers in permafrost regions: 1) supra-permafrost aquifers, lyingabove the permafrost so that the permafrost is their lower boundary; 2) intra-permafrost aquifers,found in unfrozen zones (taliks) within the permafrost; and 3) sub-permafrost aquifers, lyingbelow the permafrost so that the permafrost acts as a somewhat impermeable upper boundary.Each aquifer type may be found in unconsolidated deposits or bedrock (Sloan and van Everdingen1988).
Supra-permafrost aquifers can be a useful summer-time water supply, although they can have ahigh concentration of natural organics (humic acid). They tend to be unreliable winter watersupplies due to freezing or increasing mineralization (caused by the concentration of the mineralsin the unfrozen portion of the water) (Sloan and van Everdingen 1988).
Intra-permafrost aquifers do not experience seasonal freezing. Their size remains relativelyconstant and is influenced primarily by long-term temperature variations. Their water quality canvary from being more mineralized and containing less natural organics than supra-permafrostaquifers, to having a high degree of mineralization. The variation in water quality dependsprimarily on the source water, connections to other water bodies, and climatic temperature trend(decreasing temperatures tend to cause more water to freeze and increase the mineralconcentration of the remaining unfrozen water) (Sloan and van Everdingen 1988).
Sub-permafrost aquifers tend to have water temperatures above 0º C. In the region of discontinuous permafrost, where permafrost tends to be thin, sub-permafrost aquifers commonly occur in unconsolidated deposits. Sub-permafrost aquifers located in alluvial deposits below river valleys are widely used sources of water supplies (Sloan and van Everdingen 1988).
Frozen ground (frozen either seasonally or permanently) does retard groundwater movement, but it is not impermeableit is best described as a confining material with very low hydraulic conductivity. Unfrozen water can move through porous permafrost. Groundwater flow rates depend on the overall temperature of the system, the thermal gradient, and the available cross-sectional area of interconnected films of unfrozen water. When temperature decreases, that area becomes progressively smaller, lowering hydraulic conductivity. Fractures, on the other hand, can significantly increase the overall hydraulic conductivity of a frozen section of rock or soil. Segregated ice in permafrost, which can exist as lenses, layers, or ice wedges, can reduce hydraulic conductivity to the point were the ground is effectively impermeable (Sloan and van Everdingen 1988). Presumably, this occurs for the component of the groundwater flow that is perpendicular to the lens, layer, or wedge of segregated ice.
Lateral groundwater movement occurs in the active layer during the summer (frost-free) season, intaliks within the permafrost, and in unfrozen zones below the permafrost layer. Kane and Stein(1983) measured infiltration rates for frozen Fairbanks silt loam. They reported infiltration rates of 0.0001 centimeters per second (86 millimeters per day) under low soil moisture conditions and0.000001 centimeters per second (0.86 millimeters per day) for more moist soil.
Contaminant Transport in Permafrost
While the ice of frozen soil restricts contaminant migration, water-soluble contaminants candegrade that ice (by depressing the pore water freezing point), producing unfrozen moisture thatacts as a potential transport pathway. Nonaqueous-phase liquids (NAPLs), meanwhile, tend tomigrate though the unfrozen moisture surrounding soil particles (McCauley 2000).
In general, contaminant transport in frozen soil follows the same principles as in unfrozen soil.Freezing water reduces the diameter of the flow paths and blocks some flow completely. Buttransport can still occur through the thin films of moisture surrounding soil particles, as well asthrough unfrozen water. The extremely low temperatures of the system affect the fluid's densityand viscosity, tending to make it heavier and thicker. Contaminants in unfrozen water can depressthe freezing point to prevent the formation of ice or melt ice within their flow path.
Andersland et al. (1996) concluded from field studies that ice-saturated soil barriers withtemperatures below a contaminant's freezing point depression would effectively impedecontaminant flow. Biggar et al. (1998) found that diesel fuel migrated through permafrost via airvoids in unsaturated fill material, through soil fissures resulting from soil contraction duringfreezing, and beneath punctured synthetic liners.
McCauley (2000) measured the infiltration rate of a Diesel #2/Jet A-50 fuel mixture (heating oil)in frozen soil in a field test using a double ring infiltrometer (whose inner ring was 5 feet by 5feet). Field conditions were expected to represent ice-saturated, frozen soil. The averageinfiltration rate was 0.000000043 centimeters per second (0.037 millimeters per day) over the testperiod of almost 40 days. During the test period the infiltration rate dropped from approximately0.0000001 to 0.00000001 centimeters per second (0.086 to 0.0086 millimeters per day).
McCauley (2000) also measured the hydraulic conductivity of frozen and unfrozen soil samples inthe laboratory using a mixture of Diesel #2/Jet A-50 fuel. For unfrozen soil samples the hydraulicconductivity varied little between the three soil types tested: approximately 0.001 centimeters persecond (860 millimeters per day) for organic-rich silty sand, sandy silt, or silty-sand fill material.The same range of hydraulic conductivity was measured at approximately 35 percent saturationand 100 percent saturation. At low saturation levels (approximately 40 percent, corresponding to avolumetric water content of about 15 percent), the hydraulic conductivity of the frozen soil wasbetween 0.0001 and 0.001 centimeters per second (86 to 860 millimeters per day). For all threesoil types, the hydraulic conductivity of the frozen soil dropped dramatically (and almost linearly)with increasing saturation. At 100% saturation, the hydraulic conductivity of frozen soil sampleswas approximately 0.000000005 centimeters per second (0.004 millimeters per day). In these tests, the soil sampleswere completely saturated with clean water; under natural environmental conditions, complete icesaturation might be difficult due to increasing salt concentrations in the remaining unfrozen water.
Contaminant Transport on Fort Wainwright and Discontinuous Permafrost
The work of McCauley (2000) indicates that permafrost or seasonally frozen ground cannot beexpected to act as a barrier to hydrocarbon transport, with the possible exception of when thefrozen soil is fully saturated with ice. For relatively large areas, it is best to assume that frozen soilrepresents at best a leaky confining layer, until measurements indicate that the frozen soil is actingas a true barrier to contaminant transport. All of the Fort Wainwright contaminated sites wouldqualify as "large" for this analysis.
Lawson et al. (1998) summarized ongoing hydrogeological investigations conducted in the north-central area of the cantonment of Fort Wainwright. Most of their work was centered on thelandfill that was built around 1950 on discontinuous permafrost. They used a variety oftechniques, including 1) ground-penetrating radar to outline the three-dimensional locations ofpermafrost and groundwater in this area; 2) boreholes drilled at test sites to define subsurfacematerial types; and 3) groundwater monitoring wells in thawed zones located above, below, andwithin the permafrost to gather information about the groundwater flow direction and velocity.Their results suggest that the extent and thickness of the permafrost varies greatly across thenorth-central cantonment area and can cause significant deviations from the regional groundwaterflow patterns.
According to evidence presented by Lawson et al. (1998) and by works they reference, FortWainwright lies in a flood plain created by historical versions of the Chena and Tanana Rivers.Unconsolidated material lies above bedrock that slopes downward from Birch Hill toward theChena River. The unconsolidated material just north of the Chena and between the Chena and theTanana is believed to have originated as alluvial deposits, most likely in the form of braidedstreams. These sediments may influence the reported west-northwest regional groundwater flowdirection. Groundwater flow just north of the Chena, from the north-central cantonment area ofFort Wainwright to Birch Hill, may be locally diverted from the regional flow path by a north-northeast to south-southwest-trending buried bedrock valley that extends from Birch Hill towardthe Chena and the discontinuous permafrost.
Similar local diversions from the regional groundwater flow path are expected to be possible forall areas of Fort Wainwright, especially those north of the Chena River; however they are notexpected to affect contaminant transport for long distances from the source area. The two greatestconcerns are 1) the potential for contaminants released into a supra-permafrost aquifer to migrateinto the sub-permafrost aquifer via a talik, causing undetected contamination of the sub-permafrost aquifer; and 2) undetected contamination in off-base drinking water wells locatedalong the northeastern and northwestern base boundaries. The combination of information gainedfrom Lawson et al. (1998) and McCauley (2000) suggests that local diversions from the regionalgroundwater flow pattern are more common north of the Chena River, because of that area'sburied bedrock gullies and higher probability of permafrost and seasonally frozen soil. The samesources lead ATSDR to expect that most of the contaminants found at Fort Wainwright (fuels,solvents, and metals) can migrate through frozen soil.
Andersland OB, Wiggert DC, Davies SH. 1996. Frozen soil subsurface barriers: formation and iceerosion. J Contam Hydrol 23(2):133-47. Cited in McCauley CA. 2000. Fuel penetration rates infrozen and unfrozen soils: Bethel, Alaska. Master of Science thesis. Fairbanks: University ofAlaska Fairbanks.
Biggar KW, Haidar S, Nahir M, Jarrett PM. 1998. Site investigations of fuel spill migration intopermafrost. J Cold Reg Eng 12(2):84-104.Cited in McCauley CA. 2000. Fuel penetration rates infrozen and unfrozen soils: Bethel, Alaska. Master of Science thesis. Fairbanks: University ofAlaska Fairbanks.
Ferrians OJ, Jr. 1965. Permafrost map of Alaska. U.S. Geological Survey MiscellaneousGeological Investigations Map I-445. Cited in Lawson DE, et al. 1998. Geological andgeophysical investigations of the hydrogeology of Fort Wainwright, Alaska, Part II: north-centralcantonment area. Hanover, New Hampshire: U.S. Army Corps of Engineers, Cold RegionsResearch and Engineering Laboratory. City of Publisher: name of publisher. (CRREL Report 98-6.)
Kane DL, Stein J. 1983. Master of Science thesis: Physics of snowmelt infiltration into seasonallyfrozen soils. Proceedings: advances in infiltration. Chicago: American Society of AgriculturalEngineers. p. 178-87. Cited in McCauley CA. 2000. Fuel penetration rates in frozen and unfrozensoils: Bethel, Alaska. Master of Science thesis. Fairbanks: University of Alaska Fairbanks.
Lawson DE, Arcone SA, Delaney AJ, Strasser JD, Strasser JC, Williams CR, Hall TJ. 1998.Geological and geophysical investigations of the hydrogeology of Fort Wainwright, Alaska, PartII: north-central cantonment area. Hanover, New Hampshire: U.S. Army Corps of Engineers, ColdRegions Research and Engineering Laboratory. (CRREL Report 98-6.)
McCauley CA. 2000. Fuel penetration rates in frozen and unfrozen soils: Bethel, Alaska. Masterof Science thesis. Fairbanks: University of Alaska Fairbanks.
Sloan CE, van Everdingen RO. 1988. Region 28, permafrost region. In: Back W, Rosenshein JS,Seaber PR, editors. The geology of North America, Volume O-2: Hydrogeology. Boulder,Colorado: The Geological Society of America.
USGS (U.S. Geological Survey). 1999. Ground water atlas of the United States: Alaska, Hawaii,Puerto Rico, and the U.S. Virgin Islands. Washington: U.S. Geological Survey. (Pub. #HA 730-A) (http://capp.water.usgs.gov/gwa/ch_n/N-AKtext1.html)
Williams JR. 1970. Ground water in the permafrost regions of Alaska. U.S. Geological SurveyProfessional Paper 696. Cited in Lawson DE, Arcone SA, Delaney AJ, Strasser JD, Strasser JC,Williams CR, Hall TJ. 1998. Geological and geophysical investigations of the hydrogeology ofFort Wainwright, Alaska, Part II: north-central cantonment area. Hanover, New Hampshire: U.S.Army Corps of Engineers, Cold Regions Research and Engineering Laboratory. CRREL Report98-6.
- How a chemical enters a person's blood after the chemical has been swallowed, has come into contact with the skin, or has been breathed in.
- Acute Exposure:
- Contact with a chemical that happens once or only for a limited period of time. ATSDR defines acute exposures as those that might last up to 14 days.
- Adverse Health Effect:
- A change in body function or the structures of cells that can lead to disease or health problems.
- The Agency for Toxic Substances and Disease Registry. ATSDR is a federal health agency in Atlanta, Georgia that deals with hazardous substance and waste site issues. ATSDR gives people information about harmful chemicals in their environment and tells people how to protect themselves from coming into contact with chemicals.
- Background Level:
- An average or expected amount of a chemical in a specific environment. Or, amounts of chemicals that occur naturally in a specific environment.
- Used in public health, things that humans would eat - including animals, fish and plants.
- Any substance shown to cause tumors or cancer in experimental studies.
- See Comprehensive Environmental Response, Compensation, and Liability Act.
- Chronic Exposure:
- A contact with a substance or chemical that happens over a long period of time. ATSDR considers exposures of more than one year to be chronic.
- Completed Exposure Pathway:
- See Exposure Pathway.
- Comparison Value (CVs):
- Concentrations or the amount of substances in air, water, food, and soil that are unlikely, upon exposure, to cause adverse health effects. Comparison values are used by health assessors to select which substances and environmental media (air, water, food and soil) need additional evaluation while health concerns or effects are investigated.
- Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA):
- CERCLA was put into place in 1980. It is also known as Superfund. This act concerns releases of hazardous substances into the environment, and the cleanup of these substances and hazardous waste sites. ATSDR was created by this act and is responsible for looking into the health issues related to hazardous waste sites.
- A belief or worry that chemicals in the environment might cause harm to people.
- How much or the amount of a substance present in a certain amount of soil, water, air, or food.
- See Environmental Contaminant.
- Dermal Contact:
- A chemical getting onto your skin. (see Route of Exposure).
- The amount of a substance to which a person may be exposed, usually on a daily basis. Dose is often explained as "amount of substance(s) per body weight per day".
- The amount of time (days, months, years) that a person is exposed to a chemical.
- Environmental Contaminant:
- A substance (chemical) that gets into a system (person, animal, or the environment) in amounts higher than that found in Background Level, or what would be expected.
- Environmental Media:
- Usually refers to the air, water, and soil in which chemcials of interest are found. Sometimes refers to the plants and animals that are eaten by humans. Environmental Media is the second part of an Exposure Pathway.
- U.S. Environmental Protection Agency (EPA):
- The federal agency that develops and enforces environmental laws to protect the environment and the public's health.
- Coming into contact with a chemical substance.(For the three ways people can come in contact with substances, see Route of Exposure.)
- Exposure Assessment:
- The process of finding the ways people come in contact with chemicals, how often and how long they come in contact with chemicals, and the amounts of chemicals with which they come in contact.
- Exposure Pathway:
- A description of the way that a chemical moves from its source (where it began) to where and how people can come into contact with (or get exposed to) the chemical.
ATSDR defines an exposure pathway as having 5 parts:
- Source of Contamination,
- Environmental Media and Transport Mechanism,
- Point of Exposure,
- Route of Exposure, and
- Receptor Population.
When all 5 parts of an exposure pathway are present, it is called a Completed Exposure Pathway. Each of these 5 terms is defined in this Glossary.
- How often a person is exposed to a chemical over time; for example, every day, once a week, twice a month.
- Hazardous Waste:
- Substances that have been released or thrown away into the environment and, under certain conditions, could be harmful to people who come into contact with them.
- Health Effect:
- ATSDR deals only with Adverse Health Effects (see definition in this Glossary).
- Indeterminate Public Health Hazard:
- The category is used in Public Health Assessment documents for sites where important information is lacking (missing or has not yet been gathered) about site-related chemical exposures.
- Swallowing something, as in eating or drinking. It is a way a chemical can enter your body (See Route of Exposure).
- Breathing. It is a way a chemical can enter your body (See Route of Exposure).
- Minimal Risk Level. An estimate of daily human exposure - by a specified route and length of time -- to a dose of chemical that is likely to be without a measurable risk of adverse, noncancerous effects. An MRL should not be used as a predictor of adverse health effects.
- The National Priorities List. (Which is part of Superfund.) A list kept by the U.S. Environmental Protection Agency (EPA) of the most serious, uncontrolled or abandoned hazardous waste sites in the country. An NPL site needs to be cleaned up or is being looked at to see if people can be exposed to chemicals from the site.
- No Apparent Public Health Hazard:
- The category is used in ATSDR's Public Health Assessment documents for sites where exposure to site-related chemicals may have occurred in the past or is still occurring but the exposures are not at levels expected to cause adverse health effects.
- No Public Health Hazard:
- The category is used in ATSDR's Public Health Assessment documents for sites where there is evidence of an absence of exposure to site-related chemicals.
- Public Health Assessment. A report or document that looks at chemicals at a hazardous waste site and tells if people could be harmed from coming into contact with those chemicals. The PHA also tells if possible further public health actions are needed.
- A line or column of air or water containing chemicals moving from the source to areas further away. A plume can be a column or clouds of smoke from a chimney or contaminated underground water sources or contaminated surface water (such as lakes, ponds and streams).
- Point of Exposure:
- The place where someone can come into contact with a contaminated environmental medium (air, water, food or soil). For examples:
the area of a playground that has contaminated dirt, a contaminated spring used for drinking water, the location where fruits or vegetables are grown in contaminated soil, or the backyard area where someone might breathe contaminated air.
- A group of people living in a certain area; or the number of people in a certain area.
- Public Health Assessment(s):
- See PHA.
- Public Health Hazard:
- The category is used in PHAs for sites that have certain physical features or evidence of chronic, site-related chemical exposure that could result in adverse health effects.
- Public Health Hazard Criteria:
- PHA categories given to a site which tell whether people could be harmed by conditions present at the site. Each are defined in the Glossary. The categories are:
-Urgent Public Health Hazard
-Public Health Hazard
-Indeterminate Public Health Hazard
-No Apparent Public Health Hazard
-No Public Health Hazard
- Receptor Population:
- People who live or work in the path of one or more chemicals, and who could come into contact with them (See Exposure Pathway).
- Reference Dose (RfD):
- An estimate, with safety factors (see safety factor) built in, of the daily, life-time exposure of human populations to a possible hazard that is not likely to cause harm to the person.
- Route of Exposure:
- The way a chemical can get into a person's body. There are three exposure routes:
- breathing (also called inhalation),
- eating or drinking (also called ingestion), and
- or getting something on the skin (also called dermal contact).
- The Superfund Amendments and Reauthorization Act in 1986 amended CERCLA and expanded the health-related responsibilities of ATSDR. CERCLA and SARA direct ATSDR to look into the health effects from chemical exposures at hazardous waste sites.
- Source (of Contamination):
- The place where a chemical comes from, such as a landfill, pond, creek, incinerator, tank, or drum. Contaminant source is the first part of an Exposure Pathway.
- Sensitive Populations:
- People who may be more sensitive to chemical exposures because of certain factors such as age, a disease they already have, occupation, sex, or certain behaviors (like cigarette smoking). Children, pregnant women, and older people are often considered special populations.
- Harmful. Any substance or chemical can be toxic at a certain dose (amount). The dose is what determines the potential harm of a chemical and whether it would cause someone to get sick.
- The study of the harmful effects of chemicals on humans or animals.
- Urgent Public Health Hazard:
- This category is used in ATSDR's Public Health Assessment documents for sites that have certain physical features or evidence of short-term (less than 1 year), site-related chemical exposure that could result in adverse health effects and require quick intervention to stop people from being exposed.
Comparison values represent media-specific contaminant concentrations that are used to select contaminants for further evaluation to determine the possibility of adverse public health effects. The conclusion that a contaminant exceeds the comparison value does not mean that it will cause adverse health effects.
Cancer Risk Evaluation Guides (CREGs)
CREGS are estimated contaminant concentrations that would be expected to cause no more thanone excess cancer in a million (10-6) persons exposed over their lifetime. ATSDR's CREGs are calculated from EPA's cancer potency factors (CPFs).
Maximum Contaminant Level (MCL)
The MCL is the drinking water standard established by EPA. It is the maximum permissible levelof a contaminant in water that is delivered to the free-flowing outlet. MCLs are consideredprotective of public health over a lifetime (70 years) for individuals consuming 2 liters of water per day.
Environmental Media Evaluation Guides (EMEGs)
EMEGs are based on ATSDR minimal risk levels (MRLs) that consider body weight andingestion rates. An EMEG is an estimate of daily human exposure to a chemical (in mg/kg/day)that is likely to be without noncarcinogenic health effects over a specified duration of exposure to include acute, intermediate, and chronic exposures.
Reference Media Evaluation Guides (RMEGs)
ATSDR derives RMEGs from EPA's oral reference doses. The RMEG represents theconcentration in water or soil at which daily human exposure is unlikely to result in adverse noncarcinogenic effects.
Overview of ATSDR's Methodology for Evaluating Potential Public Health Hazards
The health hazards that could plausibly result from exposures to contaminants detected in FortWainwright and the area are discussed in further detail in this appendix. It is important to notethat public health hazards from environmental contamination happen only when (a) people areexposed to the contaminated media and (b) the exposure is at high enough doses to result in aneffect.
Selecting Exposure Situations for Further Evaluation
As an initial screen, ATSDR evaluated availabledata to determine whether contaminants wereaccessible to the public or were above ATSDR'scomparison values. The majority of detectedcontaminants were either not accessible to thepublic or fell at or below comparison values andwere not evaluated further (see text box for adescription of comparison values). Exposuresituations with contaminants above comparisonvalues or that had insufficient environmental datawere deemed worthy of further evaluation. These exposure situations include the following:
- Past Exposure to contaminants in drinking water at the nearby private church wells
- Exposure air pollutants from the coal-fired power plant
- Exposure to coal ash used as road grit
- Exposure to material at the tar sites
Deriving Exposure Doses
After identifying potential exposure situations, ATSDR further evaluated exposures tocontaminants in media considering information about exposures combined with scientificinformation from the toxicologic and epidemiologic literature. If necessary, ATSDR derivedexposure doses, which are estimates of how much contaminant a person is exposed to on a dailybasis. Exposure doses are expressed in milligrams per kilogram per day (mg/kg/day). Thisrepresents the amount of contaminant mass that an individual is assumed to inhale, ingest or touch(in milligrams), divided by the body weight of the individual (in kilograms) each day. Whenestimating exposure doses, health assessors evaluate chemical concentrations to which peoplecould be exposed, together with the length of time and the frequency of exposure. Variablesconsidered when estimating exposure doses include the contaminant concentration, the exposureamount (how much), the exposure frequency (how often), and the exposure duration (how long).
Using Exposure Doses to Evaluate Potential Health Hazards
If situations are identified where individuals would be expected to come into contact with siterelated contaminants, during the course of their normal activities, on a regular basis, ATSDRevaluates the potential for the exposure to cause a public health hazard. When evaluating potentialhealth hazards, ATSDR analyzes the available toxicologic, medical, and epidemiologic data todetermine whether exposures might be associated with harmful health effects (noncancer andcancer). As part of this process, ATSDR examines relevant health effects data to determinewhether estimated doses are likely to result in harmful health effects. As a first step in evaluatingnoncancer effects, ATSDR compares estimated exposure doses to conservative health guidelinevalues, including ATSDR's minimal risk levels (MRLs) and EPA's reference doses (RfDs). TheMRLs and RfDs are estimates of daily human exposure to a substance that are unlikely to result innoncancer effects over a specified duration. Estimated exposure doses that are less than thesevalues are not considered to be of health concern. To maximize human health protection, MRLsand RfDs have built in uncertainty or safety factors, making these values considerably lower thanlevels at which health effects have been observed. The result is that even if an exposure dose ishigher than the MRL or RfD, it does not necessarily follow that harmful health effects will occur.
For carcinogens, ATSDR also calculates a theoretical increase of cancer cases in a population (forexample, 1 in 1,000,000 or 10-6) using EPA's cancer slope factors (CSFs), which represent therelative potency of carcinogens. This is accomplished by multiplying the calculated exposure doseby a chemical-specific CSF. Because they are derived using mathematical models which apply anumber of uncertainties and conservative assumptions, risk estimates generated by using CSFstend to be overestimated.
If health guideline values are exceeded, ATSDR examines the health effects levels discussed inthe scientific literature and more fully reviews exposure potential. ATSDR reviews availablehuman studies as well as experimental animal studies. This information is used to describe thedisease-causing potential of a particular chemical and to compare site-specific dose estimates withdoses shown in applicable studies to result in illness (known as the margin of exposure). Forcancer effects, ATSDR compares an estimated lifetime exposure dose to available cancer effectslevels (CELs), which are doses that produce significant increases in the incidence of cancer ortumors, and reviews genotoxicity studies to understand further the extent to which a chemicalmight be associated with cancer outcomes. This process enables ATSDR to weigh the availableevidence in light of uncertainties and offer perspective on the plausibility of harmful healthoutcomes under site-specific conditions.
Sources for Health-Based Guidelines
By Congressional mandate, ATSDR prepares toxicological profiles for hazardous substances found at contaminated sites. These toxicological profiles were used to evaluate potential health effects from contamination at Fort Wainwright. ATSDR's toxicological profiles are available on the Internet at http://www.atsdr.cdc.gov/toxpro2.html or by contacting the National Technical Information Service at 1-800-553-6847. EPA also develops health effects guidelines, and in some cases, ATSDR relied on EPA's guidelines to evaluate potential health effects. These guidelines are found in EPA's Integrated Risk Information System (IRIS)a database of human health effects that could result from exposure to various substances found in the environment. IRIS is available on the Internet at http://www.epa.gov/iris. For more information about IRIS, please call EPA's IRIS hotline at1-301-345-2870 or e-mail at Hotline.IRIS@epamail.epa.gov.
- Evaluation of Potential Public Health Hazards From Ingesting Shannon Park Baptist Church Well and Steese Chapel Hall Well Water in the Past
The contaminant 1,2-dichloroethane (1,2-DCA) was detected in the Shannon Park Baptist Churchand the Steese Chapel Hall wells in 1991 at concentrations greater than ATSDR comparisonvalues for drinking water. The primary exposure pathway of concern was past exposure to thisVOC is through consumption of the private well water. No exposure via consumption is occurringnow because the wells are not being used for drinking water. Because church members possiblydrank water drawn from the church wells in the past, ATSDR evaluated the health effects frompast ingestion exposure to 1,2-DCA in drinking water.
In estimating to what extent people might be exposed to contaminants, ATSDR used protective assumptions about how long people were exposed to contaminants and how much contaminated water they ingested each day. Because some uncertainty exists regarding how long the contaminants have been in the private wellsno sampling data prior to 1991ATSDR conservatively assumed that an adult was exposed to the contaminant for the period the Shannon Park Baptist Church well was in use (1985-1991). (Less is known about the use history of the Steese Chapel Hall well.) In all likelihood, the wells have been contaminated for less than 7 years. Adults were assumed to drink about 2 quarts (2 liters) of tap water each day and to weigh (on average for male and female) about 150 pounds (or 70 kilograms). Children were assumed to drink about one quart (1 liter) of tap water each day and to weigh roughly 35 pounds (16 kg). ATSDR assumed that private well owners obtained all their daily fluids from this private well. This is likely another conservative assumption because individuals tend to get some of their liquid requirements from sources such as milk, juice, soda, and a variety of foods. Furthermore, ATSDR assumed that church members were exposed to the most contaminated water; therefore, ATSDR used the highest (or maximum) measured concentrations of contaminants in the private well. The highest detected concentrations of 5.86 ppb was actually reported in 1995, after use of the well was discontinued. These assumptions create a protective estimate of exposure, and together, allow ATSDR to safely evaluate the likelihood, if any, that contaminants in private well water could cause harm to its users.
ATSDR also reviewed the scientific literature to further evaluate potential health effectsassociated with exposure to 1,2-DCA-contaminated drinking water at the detected concentrations.Most of the toxicologic and health effects information reviewed by ATSDR came fromexperimental animal studies or from epidemiologic investigations (human data) that examined therelationship between these contaminants in drinking water supplies and various health effects.
Applying conservative assumptions allows ATSDR to estimate the highest possible exposure doseand determine the corresponding health effects. Although ATSDR expects that few, if any,residents were exposed to the highest contaminant concentrations, the "conservative" estimatesare used to protect public health. ATSDR used the following equation and assumptions toestimate exposure doses:
= Maximum concentration (milligrams of chemical per liter water [mg/L]).
ATSDR assumed that people ingested water containing the highest detected levels of 1,2-DCA (5.86 ppb, which equals 0.00586 mg/L). This assumption is designed to overestimate exposures. Concentrations may have fluctuate over time. As such, people may have been exposed to water that contained the maximum detected concentrations, but they also may have been exposed to water with lower contaminant concentrations or may have consumed water free of contamination.
= Intake rate: 2 liters per day (L/day) for adults, 1 L/day for children.
The intake rate represents the amount of liquids that a person would drink in a single day. The average adult drinks 1.4 liters of water a day and the average child, aged 3 or younger, drinks 0.6 liters of liquid each day (EPA 1997). This assumption overestimates exposures because people likely obtain water from sources other then their drinking water wells (e.g., prepackaged soda or juice; bottled water; or wells serving stores, businesses, or schools).
= Exposure frequency: 365 days per year (day/yr).
For members of the church, ATSDR assumed that exposures occurred every day, although daily exposures are unlikely since most people are expected to visit the church during hours of worship.
|ED||= Exposure duration: 7 years (yrs) to account for the time the well was installed (1985) until the well use was discontinued (1991) following the detection of 1,2-DCA.|
= Body weight: 70 kilograms (kg), which equals 154 pounds, for adults and 16 kg, which equals 35 pounds, for children
No site-specific information is available to characterize the average weight of people living at or near The Shannon Park Baptist Church. ATSDR reviewed the scientific literature and used the U.S. Environmental Protection Agency's (EPA) recommended default weight for an adult (70 kg) and child (10 kg) (EPA 1997).
= Averaging time: 2,555 days (7 yrs x 365 days/yr) for non-cancer effects to adults and children.
In assessing non-cancer effects, the averaging time is equal to the exposure duration. In assessing cancer effects, the averaging time is equal to a person's life span.
Noncancer Health Effects
ATSDR compared the estimated exposure doses to dose-based CVs to assess potential non-cancereffects. Dose-based CVs (referred to as minimal risk levels [MRLs] by ATSDR and referencedoses [RfDs] by EPA) are contaminant-specific doses that are conservatively derived based on the health effects literature and are below the levels associated with adverse health effects.
Table D-1 summarizes the conservative doses of 1,2-DCA estimated for consumption of drinkingwater and the dose-based CVs. Doses for people drinking water from the church well between1985 and 1991 were below dose-based CVs. Because of the conservative assumptions used toestimate a dose, the true dose is expected to be even much lower than the estimated dose. As such,possible past exposures to 1,2-DCA is not expected to result in adverse health effects for adults orchildren who drank water from church well in the past. No exposure has occurred since 1991when use as a drinking water supply was discontinued.
|Intermediate Minimal Risk Level |
ATSDR estimated a theoretical excess cancer risk expressed as the proportion of a population thatmay be affected by a carcinogen during a lifetime of exposure. In assessing cancer risks, scientistsassume that any exposure to a carcinogen could result in a possible cancer case. However,information about the likelihood of developing cancer is based on studies where animals orhumans have been exposed to high concentrations of a contaminants, levels much higher thanwould occur as a result of environmental releases. This assumption that any contact with acarcinogen could lead to cancer is extremely conservative. Scientists assume that the theoreticalcancer risk can never be zero, whereas the true or actual risk is unknown and could be as low aszero (EPA 1996).
The theoretical cancer risk for exposures to carcinogens from the church well water in the past was below 10-4 (1 additional cancer over background in a population of 10,000)a level used as a guideline for exposure doses that are below levels of concern. Little information exists in the medical literature about the development of cancer in people who consumed 1,2-DCA. EPA has, however, classified 1,2-DCA as a probable human carcinogen based on evidence from laboratory animal studies (ATSDR 2001). In these studies, animals were fed large doses of 1,2-DCA, but at levels at least 16 times greater than those detected in the church well water. Based on this finding, ATSDR does not consider increased likelihood of developing cancer from 1,2-DCA a concern for people who consumed water from the church well. Furthermore, ATSDR strongly emphasizes that no public health hazard exist now because no one is or expected to in the future drink water from the well.
- Evaluation of Potential Public Health Hazards from the Coal-Fired Power PlantEmissions
The Fort Wainwright coal-fired power plant supplies heat and electricity for the post, and burnsapproximately 300 tons of coal per day during the summer and up to 1,200 tons of coal per day inthe winter. The power plant appears to be a little less than 2 miles east of the western boundary ofthe Fort Wainwright. The Chena school is a little over ½ mile west of the power plant. The nearestboundary of the closest on-post housing is also about ½ mile west of the power plant. Another on-post housing area is located a little over 1 mile north of the power plant, while an off-base housingarea is a little over 1 mile to the northwest. The average wind direction in Fairbanks is from the southwest, orsouthwesterly, during the summer (June-August) and from the north, or northerly, during the restof the year (CH2M Hill 1994).
The ADEC twice issued notices to Fort Wainwright (in 1994 and 1996) for air pollutionviolations (EPA 1999) and EPA issued a Notice of Clean Air Act Violation to the coal-firedpower plant on March 10, 1999. At the time of the 1999 inspection, the plant was operatingwithout adequate emission controls and functioning monitors (EPA 1999). Also, from the 1960sto 1993, the coal pile used for fuel at the plant was sprayed with waste petroleum fuel products,such as diesel, fuel oil, solvents, and lubricants from tanks, railroad cars, and drums while storedat the Coal Storage Yard. The oil was used to increase the British thermal unit content of the coaland ultimately improve the output of the coal fired-power plant (EPA 1996).
No ambient air monitoring data have been identified for Fort Wainwright. Two ambient airmonitors were installed near the power plant and began operating in February 2003. The northmonitoring station is approximately 480 feet northeast of the plant. The south station isapproximately 1500 feet southwest of the plant. Both monitors are approximately 15 feet aboveground level. Results indicate these sites meet National Ambient Air Quality Standards for sulfurdioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO) and PM10 (Siftar 2003a; personalcommunication). Ambient air monitoring information for carbon monoxide and particulate matterfor the city of Fairbanks, west of the post, was available from the EPA AirData database for theyears 1996 to 2001. The measured ambient air concentrations at the nearest station (located 1 milewest of the base) never exceeded the 1-hour EPA Air Quality Standard for carbon monoxide, andexceeded the 8-hour standard only four times in 6 years. Particulate matter never exceeded the 24-hour average EPA Air Quality Standard or the annual mean air quality standard in 6 years (EPA2002a).
The EPA air monitoring results suggest that the air quality in the Fairbanks area is not adverselyimpacted by carbon monoxide or particulate matter emissions; however this monitor is locatedabout 3 miles from the power plant and several residential communities are located within one mile ofthe power plant. ATSDR believes that the available air monitoring data does not directly evaluatethe potential public health impact of air emissions from the Fort Wainwright coal-fired powerplant during normal operations or while it was also burning waste oil. ATSDR is, therefore,concerned that residential communities located near the power plant may be exposed to higherlevels of pollutants than that indicated by the Fairbanks air monitor, especially when the powerplant is not operating with adequate emission controls and functioning monitors.
To complete its assessment, ATSDR reviewed background information and used a screening airmodeling analysis to identify if the air quality in these communities could be impacted by thepower plant to a greater extent than predicted by the Fairbanks air monitoring results. Wereviewed background information on the emissions from coal fired power plants, and themeasured effects of those emissions on the air quality of other communities surrounding coal firedpower plants, to identify if any of the contaminants released could affect the local air quality atlevels that could lead to public health concerns. Limited air modeling was also conducted toidentify if the on-post, or nearby off-post residential communities would be expected to havesignificantly higher concentrations of particulate matter than those measured at the Fairbanksmonitoring station.
Typical Coal-Fired Power Plant Emissions
Fossil fuels, predominantly coal, petroleum and gas, supply about 70% of the nation's fuelrequirement for electricity generation (DOE 2002a), and general information about coal firedpower plants is available from a variety of sources. The following sections provide some basicinformation about coal-fired power plant emissions and their effect on their local community.
A variety of gases and particulates are formed during coal combustion, the type and amount ofcontaminants released to the air depend on a combination of factors including the composition ofthe coal, coal combustion conditions and the type and condition of the air pollution controlequipment. The major gases emitted from coal fired power plants, in terms of quantity, includesulfur dioxide (SO2), nitrogen oxides (NOx) and carbon dioxide (CO2) (DOE 2002b). Each ofthese gases are a concern for different reason. Emission of SO2 is a precursor to acid rain, NOx isa precursor to both acid rain and photochemical smog, and CO2 accumulation in the atmosphere isa potential greenhouse gas linked to concerns of global climate change (DOE 2002b). Otherelements and compounds are also released, but at much lower concentrations. However, due to thevast amount of coal that is burned world wide, a significant amount of research has been devotedto identifying the other constituents and understanding their fate and transport in the environment.
One of these contaminants of greatest concern is mercury. Mercury enters the coal-fired powerplant as a constituent of the coal. Approximately 25% of this mercury leaves the plant through theflue gases into the atmosphere (Meij et al. 2002). In the U.S., power plants are the greatest sourceof mercury emissions. A study commissioned by the Maryland Department of Natural Resourcesestimated that the flue gas contains an average mercury concentration of 0.010 milligrams percubic meter (mg/m3); two-thirds in the Hg(II) form and one-third in the Hg(0) form (MarylandDepartment of Natural Resources 1999). There are currently no limits for mercury emissions frompower plants, but in 2000 the EPA proposed emission reductions (EPA 2000).
Particulate emissions are another concern; however, properly functioning air pollution controlsystems can remove significant quantities of airborne particulate matter. Nielsen and Livbjerg(2002) reported that approximately 99.9% of the particles leaving the boiler in the flue gas wereremoved by the electrostatic precipitator and the desulfurization scrubber. The particles that didmake it past the air pollution control equipment were very small, 50 to 80% of the particles wereless than 2.5 um in diameter (PM2.5). Several of these particles contained metals that originatedin the coal (i.e., aluminum, barium, calcium, cobalt, copper, iron, lead, manganese, nickel,phosphorus, silicon, vanadium and zinc). Llorens et al (2001) performed a mass balance on themetals found in the coal prior to combustion, and in the ash after combustion. They concluded thatapproximately half of the incoming metals were retained in the ash; mercury and selenium wereemitted almost entirely to the atmosphere. Antimony, arsenic, boron, beryllium, cadmium,chromium, lead, lithium, molybdenum, tantalum, thallium, tin, uranium, vanadium, and wolframwere distributed to both the atmosphere and ash. However, it appears that the concentration of themetals is typically small and poses a far lesser public health concern than the particulate matter.
Various polycyclic aromatic hydrocarbons (PAHs) have also been identified in the flue gasfollowing coal combustion (Katoh 2002). The specific type and amount of PAHs emitted appearto be due slightly to the type of coal burned and is largely dependent on the combustionconditions. Efficient combustion, characterized by sufficient oxygen, appears to reduce theamount of PAHs emitted (Revuelta et al. 1999; Mastral et al. 2001).
The information reviewed suggests that a variety of gases and particulates are formed duringcoal combustion process, but that properly operating combustion chambers and pollution controlequipment can significantly reduce the amount of pollutants emitted from coal-fired power plants.
Typical Contribution of Coal-Fired Power Plant Emissions to Air Quality
Little information is available on the contribution of emissions from a coal-fired power plant onthe air quality of its community. Suarez and Ondov (2002) analyzed air samples from Baltimore,Maryland. Their results suggest that although local industrial sources were the major contributorsto air pollutants, some of the particulates could be linked to emissions from coal-fired powerplants. Ramadan et al. (2000) characterized the fine and course particle-size fractions collected inair samples from Phoenix, Arizona. Results suggest that the major sources of the fine particulatematter were motor vehicles, vegetation burning (wood and biomass), and coal-fired power plants.The major constituent of the particles was carbon. Soil and construction dust appeared to be theprimary sources of the coarse particles.
In both cases, the information reviewed did not specify the distance between the monitoringlocation and the nearest coal-fired power plant. Alternate sources indicate that one coal-firedpower plant is located in Baltimore County and several others are located within a 30-mile radiusof Baltimore (Clean Air Task Force 2002). No coal-fired power plants appear to be located inPhoenix, however four are located in other Arizona communities (Dresher 1976).
Mercury emissions from coal-fire plants are substantial. EPA estimated that in 1994 coal-firedpower plants emitted approximately 33% of the total amount of mercury emitted to the air by U.S.industrial sources. In addition to industrial emissions of new mercury into the atmosphere,mercury is also emitted by natural sources and previously deposited mercury (from industrial andnatural sources) is re-emitted. As a result, EPA estimated that U.S. utilities emit approximately 13to 26% of the total amount of mercury found in the air in the United States.
Some studies indicate that mercury emissions from coal-fired power plants do not necessarilyaffect local communities, but do have a global affect (Maryland Department of Natural Resources1999). These studies suggest that the emissions are spread over a very large area so that acommunity is exposed to a small amount of the contaminants emitted from its own coal-firedpower plant and a small amount of the contaminants emitted from all of the other coal-fired powerplants in the region and possibly the world. Results of these studies loosely suggest that local airquality can be affected by emissions from coal-fired power plants located both near and relativelyfar from the community.
Potential Health Hazards of Coal-Fired Power Plant Emissions on Local/ and the Global Community
EPA analyzed 67 different hazardous air pollutants believed to have a potential to affect publichealth (EPA 1998). They studied both local and distant releases and their potential to affect acommunity. EPA's evaluation of the inhalation pathway indicates that coal-fired power plantswithin the local area of a community (less than 31 miles from the power plant) have a theoreticalhazard of 0.2 additional cancer cases per 1 million exposed persons per year. This theoreticalincrease is very small and essentially indicates that properly operating local coal-fired powerplants do not represent a public health hazard.
Some of the emissions from a coal-fired power plant are believed to be dispersed far from thelocal community; which suggests that the local community is also potentially affected byemissions from coal-fired power plants located well beyond its borders. The EPA analysisconsidering the inhalation exposure to pollutants emitted from coal-fired plants within and outsideof the local community concluded that the effect of long-range pollutant transport slightlyincreases the potential public health hazard. The theoretical hazard for both local and long rangetransport of coal-fired power plant pollutants was 1.3 additional cancer cases per 1 millionexposed persons per year. In actuality, this increase is very small and not expected to result inmeasurable increase in cancer cases in most U.S. communities.
In addition to evaluating health hazards solely from inhalation exposure, EPA evaluated four ofthe high-priority pollutants for their multipathway (primarily inhalation and ingestion) exposurerisk. High priority pollutants are those that are persistent and/or bioaccumulate, and are toxic byingestion or are radioactive; where non-inhalation exposure pathways could represent a greaterpublic health hazard than the inhalation exposure. Results of the initial screening evaluation(including both inhalation and non-inhalation exposure pathways) concluded that radionuclides,mercury, arsenic, and dioxins were the pollutants with the greatest multipathway public healthhazard. Though not included in the multipathway analysis, cadmium and lead were also identifiedas potential multipathway hazards.
EPA has also used a variety of different modeling techniques to estimate the effect of mercuryexposure from multiple pathways (inhalation and ingestion), from local and long range transport.Specific results of this evaluation are highly uncertain and may be more applicable to the lower 48states than Alaska. The results suggest that most of the mercury emitted to the atmosphere isdeposited more than 30 miles away from the source. Mercury deposition to the soil and terrestrialvegetation is predicted to occur, but at levels that do not result in hazardous exposures. The majorconcern with mercury emissions, is that modeling assessments indicate there is a plausible linkbetween industrial mercury emissions and mercury found in fresh water fish.
Modeling Analysis of Ambient Air from Fort Wainwright Coal-fired Power Plant Emissions
Limited air modeling using SCREEN3, an EPA approved transport and dispersion screeningmodel, was used to get a rough idea of where the highest ground level breathing zoneconcentrations would be expected to occur and if concentrations in the ambient air near the schoolor residential housing could be impacted by emissions from the power plant. The modeling wasconducted assuming that the stack height was 80 ft (24.4 m) and the diameter was 6.85 ft (2.1 m).A sensitivity analysis was conducted to identify the effect of gas exit temperature, gas exitvelocity, building downdraft, and rural or urban modeling conditions significantly changed themaximum predicted concentration and the predicted concentration at a location ½ miledownwind.
The results of the sensitivity analysis indicate that the maximum concentration and theconcentration ½ mile downwind decreased as the gas exit temperature was increased from 370 to 450 K. Theseconcentrations also decreased as the gas exit velocity was increased from 0.1 to 10 m/s. The use ofurban as opposed to rural modeling conditions resulted in an increase in the maximum predictedconcentration (and predicted that this concentration would occur closer to the stack) and adecrease in the concentration measured ½ mile downwind. Similar results occurred when buildingdowndraft was included.
Information obtained from the National Emission Inventory (NEI) 1999 base year emissions datasuggest that the exit temperature of the Ft Wainwright coal fired power plants is approximately458 to 490 K and that the exit velocity is approximately 7.6 to 11.6 m/s.
Assuming emission factors from EPA's AP-42 (Fifth Edition, Volume I; Chapter 1, ExternalCombustion Sources, Bituminous and Subbituminous Coal Combustion) for SOx, NOx, CO, andPM10, ambient concentrations of these pollutants were estimated for downwind sensors located ½mile from the source and compared with the National Ambient Air Quality Standards (NAAQS).Results suggest that under some operating conditions the downwind concentrations could exceedNAAQS. Though not definitive, this analysis does suggest that under certain meteorologicalconditions, the outdoor air quality in the nearby residential area could be affected by emissionsfrom the power plant, especially when the plant is operating without the appropriate pollutioncontrol measures.
On the basis of the available information, it is not possible to identify, with certainty, if the nearbyresidential area was periodically exposed to contaminants released by power plant; however, thisreview does indicate that periodic exposures to contaminants released from the stack werepossible. Without knowing specific information about the type and quantity of contaminantspresent in the air in the residential neighborhood and the frequency and duration of exposure, it isnot possible to determine whether possible releases from the Fort Wainwright coal-fire powerplant were sufficient to cause health effects in the local community. Information reviewedsuggests that emissions from the power plant, however, would not be expected to adversely affectthe health the local population when the power plant is operating efficiently and properly usingthe approved pollution control equipment known to be functioning appropriately. Fort Wainwrightis currently installing additional air pollution control equipment (Siftar 2003; personalcommunication). ATSDR concludes that while the past exposures to air pollutants potentiallyreleased by the coal-fired power plant are indetermenent; Fort Wainwrights efforts to both reduceand monitor the emissions from the power plant will help keep the emissions within state andfederal regulatory limits and be protective of public health.
- Evaluation of Potential Public Health Hazards From the Coal Ash Used as Road Grit
Coal ash was used for snow and ice treatment at Fort Wainwright for an unspecified period until1992 (APVR-FW-DE-ENV, 1992). While no current or future exposures are expected, ATSDRwanted to further evaluate whether people could have been exposed to potential harmfulconstituents in coal ash when used as road grit in the past. The following evaluation of the use ofthe ash as a snow and ice road treatment was performed to identify the potential public healtheffects from this practice.
No specific environmental data exists concerning the concentration of ash resulting in the soil,ground water or air following its application to the roads. Information was found in EPA, AlaskaDepartment of Environmental Conservation, industrial (coal and power plant), academic and othergovernment web-sites that describe the nature, use, and effects of coal ash and suspension of roaddust into the air.
Background Information on Coal Ash
Coal ash is a residue from coal burning in power plants. Currently, within the U.S. more than 75million metric tons of ash is produced annually by coal burning power plants. Approximately 80%of that ash is deposited in landfills and surface impoundments (Bhumbla, 1996). Not surprisingly,universities, government agencies, and private organizations have been searching for ways torecycle the ash. Proposed and existing options include: inclusion in concrete as a buildingmaterial, as a soil additive for agricultural purposes, re-filling mine shafts, as a bed for new roadconstruction, and for use in snow and ice control.
The chemical composition and particle size distribution of the ash depends on the chemicalcomposition of the coal fuel and where the ash is deposited in the power plant. Modern powerplants typically have four sources of coal ash: fly ash, bottom ash, flue gas desulfurization sludge,and fluidized bed combustion waste. Typically, the coal is pulverized to the consistency of powderprior to combustion, and then it is blown into the boiler to be burned. The fine particulates, suchas fly ash, rise with flue gases and either settle elsewhere in the system or flow out of the stack.The larger particles fall to the bottom and are removed as the bottom ash (CPM Inc., 2000). Powerplants that use flue gas desulfurization or fluidized bed combustion processes to reduce sulfuremissions, tend to have high concentrations of sulfur in the ash from those locations.
About 16% of the coal ash produced by power plants is bottom ash (Kalyoncu, 2001). Bottom ashtends to resemble shattered glass and can be abrasive (Flygt, 2003). Several sources identified thatbottom ash was used for snow and ice control (TFHRC, 2003; CPM Inc., 2000). The U.S.Department of Transportation, Federal Highway Administration acknowledged that bottom ash isused for snow and ice control at various areas around the country; however, they do notrecommend the practice because the ash tends to have a low pH and may be corrosive to metals(DOT, 2002).
Coal Ash Use at Fort Wainwright
Though not specified in the documentation from Fort Wainwright, ATSDR believes that thesource of the road grit was the bottom ash. Fort Wainwright documents did not identify how muchcoal ash was applied at a time, the frequency of applications over the winter months, or whichroads were treated with the coal ash.
Fort Wainwright provided results of laboratory analyses of the coal composition, leach testsperformed on fly ash and ash samples (this type of test is describe in more detail in the sectionevaluating the tar sites), and 'ash' composition. ATSDR used just the ash composition test toestimate the composition of the coal ash used as road grit. Table D-2 identifies the range of thevarious metals measured in the ash and compares the measured values to the common range ofthat metal in soil and the ATSDR comparison value.
Public Health Evaluation of Potential Past Exposure to Coal Ash at Fort Wainwright
ATSDR considered three potential public health concerns related to the previous practice of usingthe coal ash as road grit. First, potential contamination of the soil lying along the road due tometals in the ash and subsequent ingestion of that soil by Fort Wainwright residents. Second,infiltration of contaminants to the groundwater and potential ingestion with drinking water. Third,inhalation of contaminants due to suspension by vehicular traffic. To evaluate these concerns,ATSDR gathered background information about typical concerns associated with coal ash appliedto ground surfaces to understand the theoretical potential of coal ash to contaminate ground waterand affect public health. In addition, ATSDR used results of the previous laboratory tests of ashand estimated application rates to evaluate the potential of the coal ash used as road grit to affect public health.
|Metal||Measured Concentration by EPA 6010||Measured Concentration by EPA 200.7 [ppm] or EPA 7471||Common Range for Soils 2||ATSDR CV for Soil|
|Arsenic||21.9||13.0||1 - 50||20 3|
|Barium||2543||4037||100 - 3000||4000 3|
|Cadmium||1.5||1.7||0.01 - 0.70||50 3|
|Lead||59.6||61.9||2 - 20||400 4|
|Mercury||2.5||5.02 1||0.01 - 0.3||6.7 5, 6|
|Selenium||<5.3||<4.4||0.1 - 2||300 3|
|Silver||<2.1||<1.8||0.1 - 5||300 3|
|1 Mercury was analyzed by EPA method 7471; all others by EPA 200.7. |
2 EPA 1987.
3 ATSDR's reference dose media evaluation guide (RMEG) for a child.
4 EPA, Region 9, Preliminary Remediation Goals (PRGs)
5 Arizona Department of Environmental Quality, soil remediation levels.
6 The WHO permissible tolerable weekly intake is 5 µg/kg; assuming a 20 kg child was eating this material, he would be able to consume up to 20 grams (g) of ash ([5 µg mercury /kg bodyweight * 20 kg bodyweight]/[5 ug mercury g/g ash]). The density of bottom ash is approximately 2.5 grams per cubic centimeter 7; 20 g of ash would be approximately 50 cubic centimeters (about 1.7 ounces, 10 teaspoons, or a little over 3 tablespoons).
7 TFHRC. 2003.
Potential Ingestion Exposure to Ash Metals in the Soil
ATSDR considered the potential for the metals measured in the ash to be ingested by childrenplaying near a roadway that had been treated with bottom ash as road grit. Concentrations of themetals are below their ATSDR comparison value (CV) for that material in soil. Both ATSDR andU.S. Environmental Protection Agency (EPA) do not have a CV for elemental mercury in soil.The concentration of mercury in the ash is below the reported soil remediation level for Arizona.In addition, significant quantities of the ash would need to be consumed on a regular basis toexceed the World Health Organization's (WHO) standard mercury ingestion. Ash transported offof the road surface by rain or vehicular traffic is expected to ultimately end up in the post's stormwater discharge system or land on neighboring property landscape. Once the ash was added to theroadway the effective concentration of the metals would be reduced as the ash mixed in thesurrounding soil. Therefore, ATSDR concludes that use of the bottom ash as road grit material didnot constitute an ingestion hazard for post residents or visitors.
Potential Exposure to Ash Metals due to Groundwater Contamination
ATSDR considered the potential for metals measured in the ash to infiltrate to the underlyinggroundwater, potentially contaminating the groundwater in that area. Again, because the metalconcentrations measured in the ash are within ATSDR CVs for soil, it is not expected to havechanged the groundwater concentration for these metals. ATSDR concludes that use of the bottomash for road grit did not cause a drinking water hazard.
Potential Exposure to Ash Metals due to Inhalation
ATSDR considered the potential for the metals measured in the ash to become airborne followingvehicle traffic on the roads. This evaluation was performed using the format described by EPA toestimate the particulate concentration following vehicle traffic on a paved road. ATSDR assumedthe most conservative, yet realistic, exposure scenario which considered air concentrations along atwo-lane road that had recently been treated with bottom ash. Under this scenario, sufficientmaterial would have been available and passing car traffic ground the grit to a small enough sizethat would permit it to become airborne. Other assumptions used in our evaluation include: theroads were dry, grit is not held to the road surface by water or ice; traffic was relatively heavy fora short period of time (vehicle speed of 35 miles per hour, one car every 2 seconds for 15minutes), similar to what might be expected near a road during rush-hour; all vehicles weresimilar to a 2003 Ford F-150, 4×4 regular cab style side truck, 4.6L V-8, 5-speed manualtransmission, curb weight of 4431 lbs (weighing about 2.2 tons) (Ford, 2003); the road had twolanes (one for each direction); vehicle traffic is primarily in one direction for the 15 minute timeperiod; the road does not have a parking lane or curb, the road surface is even with the landscape;there are no openings to the storm water drainage system along this section of road.
EPA estimates the particulate emissions from vehicle traffic on a dry paved road by:
E = k (sL/2)0.65 (W/3)1.5, where E = the particulate emission factor [g/VMT] k = particle size multiplier for particle size of interest [g/VTM] sL = road surface silt loading [g/m2] W = average weight of vehicles traveling the road [tons] VMT = vehicle miles traveled
This emission factor includes the emissions from the exhaust, brake wear, and tire wear that were released during test while developing this formula. ATSDR applied this equation using a low value of the silt loading to simulate clean road conditions and then a higher silt loading simulate worst-case road conditions following ash application. Ideally ,silt loading would be estimated based on tests of the on-post roads during the conditions simulated; however, that information is not available. Other researchers though have looked at the relationship between measured silt loading, air concentrations of PM, and the resulting emission factor for a variety of locations. Clean paved roads appear to have a silt loading of about 0.1 to 1 gram per square meter (g/m2); uncleaned city roads appear to have a silt loading of 1.0 to 3.6 g/m2 while uncleaned industrial roads can be over 10 g/m2. ATSDR assumed that clean road conditions at Fort Wainwright could be simulated by using a silt loading of 0.5 g/m2 while the silt loading following ash application could be simulated by a silt loading of 20 g/m2.
Table D-3 shows the values used for the calculation of the emission factor (EF) for airborneparticulate material with an aerodynamic diameter of 10 micrometer (µm) (or PM10) or less, forboth conditions and the resulting values. The emission factor (EF) calculated for the ash treatedroads assumes that all of the applied bottom ash is immediately ground into silt-sized particles. Ifthis were true, the ash would not be a useful method of improving traction on snow and icecovered roads. In addition snow melt, rain and traffic is expected to transport a fraction of theapplied material directly to the landscape on the side of the road. This combination of factors isexpected to reduce the EF value for the ash treated road; however we were not able to identify from the literature a reasonable reduction.
|Variable||Clean Road||Ash Treated Road|
A literature search was able to identify several researchers who have measured the PM10 concentration along a road, some have attempted to quantify the change in the measured concentration with distance from the road. Laxen et al. (2002) measured PM10 concentrations adjacent and at varying distances, up to 50 meter (m), from the edge of the road. For single lane roads the results suggest a decreasing trend from approximately 30 microgram per cubic meter (µg/m3) near the road to approximately 20 µg/m3 at a distance of 50 m from the road. The results for larger roads, with more lanes, showed a relatively constant concentration of approximately 25 µg/m3 from the roadside to approximately 95 m from the road. Researchers in England reported PM10 measurements taken near roadsides for six different roads in the Newcastle upon Tyne area. The mean 24-hr PM10 concentrations varied from a low of 15 µg/m3 to a high of 85 µg/m3. The Newcastle upon Tyne area has several significant sources of particulate emissions, therefore the concentrations presented here are a combination of background sources, vehicle emissions and suspension of road silt (Newcastle City Council, 2000).
Fitz (1998) measured the PM10 concentrations upwind and downwind of a road, before and afterstreet cleaning to investigate the effect of silt loading on local air quality. The differences betweenthe upwind and downwind concentrations were near the uncertainty of the method, suggesting thatthe increase in PM10 concentration due to the vehicle traffic was not discernable.
The Alaska Department of Environmental Conservation (ADEC) measured PM10 in a parking lotof the Lemon Creek Valley in Juneau between November 1993 and April 1994. The purpose ofthe monitoring was to check if PM10 released from wood-burning stoves and vehicle traffic onnearby sanded roads could impact the air quality of that area. Those results indicate that ambientair quality was within all National Ambient Air Quality Standards (NAAQS), suggesting thatneither wood-burning stoves or sand treated roads adversely impacted the local air quality (ADEC1996).
Results from these studies suggest that for areas with a large background sources of PM10, the reduction in PM10 concentration from the road is not as significant for areas with fewer background sources. In areas with few background sources of PM10, well traveled roads can be significant local sources of PM10. Compared to many areas, Fort Wainwright has only a few background sources of PM10, notable sources include the power plant and active flight line. It is expected that the background PM10 concentration on Ft Wainwright would be similar to those measured in Lemon Creek Valley, that had an average PM10 concentration of 7 µg/m3 and a maximum 24-hr concentration of 51 µg/m3 (the second highest 24-hr concentration was 21 µg/m3). These values are within the PM10 24-hr concentration ranges reported for other areas near roadways without grit treatment; 15 to 85 µg/m3. All of these values are well within the NAAQS 24-hour standard of 150 µg/m3.
Therefore, although it is not possible to know the actual PM10 concentration near the roadfollowing ash treatment, it is likely that the PM10 concentration was within NAAQS levels.ATSDR also considered the composition of the PM10 by assuming the percent of metals in thesuspended particulate matter would be similar to that measured in the coal ash. Table D-4 showsthe percentage of each metal measured in the coal ash and the estimated concentration of themetal in the air near the roadway, assuming that a roadway PM10 concentration of 50 ug/m3. Thefinal column of the table shows the ATSDR CV for that metal in air.
Note that the results shown in this table are purely estimates, no actual measured data exist. It ismerely an attempt to identify if ground ash from treated roads could have had excessively high concentrations of metals. Typically, the CV for a particular chemical represents the average concentration people can be exposed to for long periods of time, on a regular basis, wheretoxicological data indicate that adverse health effects are not likely. The CV presented for leaddoes not follow this definition and is not truly appropriate for this analysis. The value is from theOccupation Health and Safety Administration (OSHA) guidelines. It provides the concentrationthat healthy adults, working 8-hr shifts for 5-days per week, can be exposed to without adversehealth effects. There is no CV for residential lead air concentration, the goal is to reduce andeliminate residential lead exposure because lead can affect mental and physical development ofchildren. The estimated lead concentration in the air near the road is over 16,000 times less thatthe OSHA limit. While it is always best for children and adults to avoid unnecessary leadexposure, this estimated concentration is not likely to have caused adverse health effects.
|Metal||Ash Composition 1 |
|Estimated Air Concentration |
|Arsenic||0.002||0.001 2||0.0002 3|
|1 Highest of the EPA 6010, EPA 200.7 or EPA 7471 method, converted to percent from ppm by: Percent = (ppm/1,000,000)*100. |
2 Estimated Air Concentration = (50 ug/m3)*(.002/100%) = 0.001 µg/m3.
3 ATSDR's cancer risk evaluation guide (CREG).
4 EPA Region 9, PRG.
6 EPA Region 3, RBC.
7 OSHA; note this is an occupational 8-hr time weighted average exposure limit, not necessarily protective for residential exposures.
All of the other estimated metal concentrations are well below ATSDR's CV except for arsenic.Given that the estimated concentration is a result of high vehicle traffic, the concentration willdecrease with distance from the road. The CV typically describes a concentration that anindividual could live with for long periods of time without any adverse health effect. Short periodsof time spent at higher concentrations also do not lead to adverse health effects. Again, while it isbest to avoid unnecessary arsenic exposure, this estimated concentration is not likely to havecaused adverse health effects. As a result of this evaluation, ATSDR concludes that use of bottomash from the coal power plant did not present an inhalation health hazard for the residents of FortWainwright.
- Evaluation of Potential Health Hazards From Exposure to Contaminants at the TarSites
Four sites have been identified on the main cantonment area that contain tar apparently emergingthrough the soil surface. The public health concerns of these sites are centered on understanding1) what harmful materials exist in the tar areas, 2) whether on- or off-post drinking water wellscould be affected by the tar, and 3) whether on-post residents could incur exposure to the tar atlevels of adverse health effects. The following discussion presents an overview of tar and thenaddress each health concern individually.
Tar Sites at Fort Wainwright
The four tar sites are known as the Southgate Road, Glass Park, Chena River, and the Power Planttar sites. Table D-5 describes the location of these sites. Each tar site appears to encompassseveral hundred-thousand square feet of area. Glass Park and Chena River sites are located alongthe river, near both obvious industrial areas and/or lightly developed areas with pedestrian access.The other two sites are both located south of the runway; approximately 1,000 feet apart. (Fort Wainwright, 1991).
|Southgate Road||Located west of the South Post soccer field on the South Post parade field, near Southgate Road.|
|Glass Park||Located near the western boundary of the main cantonment area, south of the Chena River near Building 4040.|
|Chena River |
(Golf Course Site)
|Located northwest of the Post Golf Course, on the north bank of the Chena River.|
|Power Plant |
|Located west of the Coal-Fired Power Plant cooling pond, next to the railroad tracks.|
Material at the Tar Sites
The tar at the four sites described in Table D-5 is believed to be the result of previous disposal ofconstruction-related material, specifically road tar (USACE, 1995). It is unclear, however, as towhen the tar was disposed of at the sites and what, if any, other material was also disposed atthese sites. A search of the Hazardous Substances Data Bank (National Library of Medicine,2003) indicates that same basic tar-like material can be used for either roofing or road pavingconstruction. This material can be identified by a variety of different names including: asphalt,asphalt cement, bitumen, petroleum roofing tar, pitch, road asphalt, and road tar. While the termtar will be used in this document to refer to this asphalt material, it really is a misnomer. Inactuality, true tars are produced by destructive distillation of coal, oil or wood, and asphalt is aresidue of fractional distillation of crude oil (National Library of Medicine, 2003). These true tarsare not used in construction and are not likely present at the Fort Wainwright tar sites.
Depending on the distillation process, three different types of asphalt may be obtained: pavingasphalts, roofing asphalts, and asphalt-based paint. Most of the asphalt produced in the U.S. isused for paving and roofing. The major constituents of asphalt include: aliphatic compounds,cyclic alkanes, aromatic hydrocarbons, and heterocyclic compounds containing nitrogen, oxygen,and sulfur atoms (NIOSH 2000). Based on the available information, it appears that the basiccomposition of the tar is similar for both paving and roofing applications, although the twomaterials are different and not interchangeable.
When used for road paving the resulting asphalt material consists of approximately 95% (byweight) of aggregate (crushed stone, gravel or sand) and 5% asphalt cement (tar) that acts as aglue to hold the pavement together (NAPA, 2002). Typically, locally available aggregate materialis used for paving operations (NAPA, 2002). No materials associated with construction debris,such as cans of primer, paint, paint thinner, and other wall preparations, nails, lumber, asbestos,and dry wall, have been identified as being discovered in, or near, any of the tar pits.
On the basis of the available information, ATSDR concluded that tar (asphalt cement) would bethe major contaminant source and was the only material considered during the evaluation of thefour known on-post tar sites.
Potential Impacts of Tar to Drinking Water Supplies
Drinking water wells are located within a mile of two tar sites. Two heavily used post drinkingwater wells are located about 4,700 feet to the west of the Power Plant tar site and abut 4,500 feetnorthwest of the Southgate Road tar site. A lesser used well is located 1,000 feet north of thePower Plant tar site and a drinking water well used by Burger King is located about 500 feet southfrom the Southgate Road tar site. The general direction for groundwater flow for this portion ofthe post is towards the northwest.
In 1992, tar samples were collected from each of the four main tar sites and analyzed by theToxicity Characteristic Leaching Procedure (TCLP). The resulting leachate was analyzed forsemi-volatile organic compounds (SVOCs), volatile organic compounds (VOCs), pesticides, 8RCRA metals (arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver), andpolychlorinated biphenyls (PCBs). The sample collected from the Southgate Road Tar Siteshowed trace amounts of the VOCs ethylbenzene, toluene, and total xylenes; however, SVOCs,pesticides, RCRA metals, and PCBs were not detected. Samples from the Glass Park Tar Site, theChena River Tar Site, and the Power Plant Tar Site all were non-detect for SVOCs, VOCs,pesticides, and PCBs. Barium was detected at trace levels in these three sites (as high as 0.48 partper million [ppm]; below TCLP regulatory limits and ATSDR's CV for drinking water) andselenium was detected at trace levels (0.074 ppm; below TCLP regulatory limits but slightlyabove ATSDR's drinking water CV for children [0.050 ppm]) at the Power Plant Tar Site(USACE-AK 1992). The measured concentrations were well below the TCLP regulatory limits of100 and 1 ppm, respectively (40CFR261.24).
Results of those tests were used to determine that the tar would not leach contaminants to theunderlying groundwater (USACE, 1995). Based on the TCLP results, the Army, EPA and AlaskaDepartment of Environmental Conservation (ADEC) concluded that there was "no evidence that apotential source of contamination exists at these sites" and signed the No Further Action (NFA)recommendation in 1994, with the comment that future action at these sites should be coordinatedwith the Solid Waste/Pollution Prevention program of ADEC (USACE, 1995).
TCLP is a laboratory test to simulate leaching from a material that could occur in a municipallandfill. This test is not designed to identify the constituents of the material itself, but identify theprobable components of the leachate resulting from a short-term exposure (18 +/- 2 hours) to alow to moderate pH solution. The TCLP test is based on a scenario that the greatest potential forthe material to contaminate groundwater, following disposal in a municipal landfill, would occurif the material were disposed with other wastes that could acidify the infiltrating rain water. Underthis scenario, acidified infiltration water would be expected to generate the greatest concentrationof contaminants in the leachate. If the contaminant concentration of the laboratory derivedleachate is within the recommended standards, it is assumed that the material will not releasesignificant amounts of contaminants that could affect local drinking water under the scenariodescribed (EPA Method 1311; Kimmell, 1999). If the laboratory derived leachate exceeds therecommended standards, the material must be treated and disposed of as a hazardous waste.
ATSDR recognizes the value of the TCLP test to categorize a material as hazardous waste andpredict its potential to contaminate infiltrating water under certain circumstances. However,ATSDR also recognizes the limits of this test's ability to estimate the material's ability tocontaminate the underlying groundwater at a specific site. There are several site specificcharacteristics that could influence how much of a compound could be released by the tar toinfiltrating water, and how much could actually reach the underlying water table. Sitecharacteristics that could influence the amount of chemical released by the tar to the infiltratingwater include: the amount of tar at the site, amount of infiltration (during a particular rainfall, orsnowmelt event, and that occurring over the course of a year), infiltration rate, and infiltratingwater characteristics (i.e., pH). Other site characteristics would be expected to influence theamount of released chemical that actually reaches the water table. These include: site geology(i.e., whether infiltrating water flows straight down to the water table or meanders slowly throughthe soil, and if the released chemicals are sorbed to the soil particles so that their movement isretarded in comparison to the infiltrating water), and depth from the tar to the water table. Giventhe difficulties in using the TCLP results to identify and estimate the concentration ofcontaminants in the groundwater beneath, and downgradient, of the tar sites ATSDR would preferto evaluate results of groundwater sampling from monitoring wells located beneath or justdowngradient of the tar sites when assessing potential health hazards.
Limited groundwater monitoring data are available for these sites as follows:
Glass Park Tar Site. A monitoring well near the Glass Park tar site (AP-12/5525) appearsto be located between the tar site and Building 4051. An underground storage tank (UST300) exists near the building, but no environmental data for this site was identified. Theexpected groundwater flow direction for this area is toward the river. Therefore, themonitoring well is likely upgradient from the tar site (groundwater would likely flow firstpast the well and then towards the tar). At this site, the river surface is about 10 feet belowthe edge of the park; basically the tar site is on the top of a small cliff overlooking theriver. Samples taken from this well during June and July of 1990, suggest bariumconcentrations in the groundwater could be above ATSDR's comparison values (CVs) fordrinking water. However, the source of the barium is not known and could be due tonatural conditions or influenced by the sources other that the tar site. This water is notused for drinking so there is no public health concern with the elevated levels of barium orother contaminants.
Chena River Tar Site. One monitoring well appears to be located within the tar site (AP-26/5538), another appears to be located between the tar site and the river bank (AP-27/5539). The Beacon Tower Landfill is located about 1,000 ft northeast of the tar site.This area was reportedly used as a landfill during the 1950s and 1960s. A NFArecommendation was signed in June 1992 because site inspections did not find enoughevidence to indicate that the landfill actually existed. If the landfill does not exist,contaminants measured in these two wells are presumably due to natural processes or areinfluenced by the tar. The well believed to be within the tar site was sampled for metals,volatile organic compounds and semivolatile organic compounds in 1989; arsenic, barium,and lead were detected above ATSDR CVs. The well believed to be outside of the tar sitehad no contaminant detected above ATSDR CVs. This water is also not used for drinkingso there are no public health concerns associated with the metal concentrations measured.
Power Plant and Southgate Tar Sites. These sites are located within 1 mile of drinkingwater supply wells. No monitoring wells are located within, or immediately downgradientof the Power Plant or Southgate Road tar sites. The closest downgradient wells appear tobe approximately 2,000 to 3,000 feet away and have the potential to be impacted by othersources, such as the power plant coal storage yard. Given the results collected at the othertar sites, it seems likely that the Power Plant and Southgate Road tar sites also have thepotential to increase the concentration of some metals in underlying groundwater. (It isimportant to note, however, that concentrations of metals in the groundwater could be theresult of natural processes in this area.) Based on the relative position of these two tar sitesand general information about the pumping rates used by the supply wells (provided in thedraft wellhead protection plan), ATSDR believes while the dominant groundwater flowdirection is likely still toward the northwest, significant variations to that direction canoccur both temporally and spatially. If the contaminants are infiltrating from the tar,however, it is likely that the concentrations will decrease rapidly as a result of dispersion,or mixing, of the tar-contaminated water with distance from the site.
Overall, there is not enough available information to determine whether or to what extentcontaminants are leaching from the Power Plant or Southgate Road tar sites (site within a mile ofthe drinking water supply wells) at a level that could affect groundwater quality. The FortWainwright Department of Public Works, however, has an active program to test the on-postdrinking water supply. These results indicate that the post drinking water has met safe drinkingwater standards. Based on the expected results of routine drinking water quality testing program,ATSDR concludes that the tar sites are not a public health hazard for the post's drinking watersupply.
Potential Hazards from Contact with Material at the Tar Sites
Public access to these sites is not restricted by fences, and signs are not posted to limit activities atthe tar sites. Some sites, such as the Southgate Road tar site, are even easily accessible bypedestrians. ATSDR reviewed the toxicologic literature on health effects from contact with tar toidentify if routine contact with the tar could be expected to cause health effects. Laboratory testsof raw roofing tar applied to the skin of mice yield conflicting results. One study concluded thatthe roofing tar led to malignant skin tumors in the treated mice, yet the other study concludedroofing tar was not carcinogenic. However, these tests were performed to identify potentialhazards to occupational exposure of the tar material. Limited data are available that describepotential human health effects resulting from dermal contact with tar and are limited to theexposure of workers to the tar, particularly, molten tar.
Occupational exposure to the fumes have been reported to cause dermatitis, acne,photosensitization, and dermal melanosis (POISINDEX(R), 1993). The primary immediatehazards for workers are burns to the skin by direct contact with the molten tar, and nose and throatirritation due to inhalation of fumes from the hot tar. A few studies did find non-dermal issues,such as a slight elevation among asphalt workers for respiratory diseases (Randem et al., 2003a),lung cancer (Randem et al., 2003b, Stucker et al., 2003), or stomach cancer (Stucker et al., 2003);though these researchers are quick to point out that the potential increases are very small andcould be confounded by other lifestyle factors such as smoking. Other studies suggest that there isno significant adverse health effects from these occupational exposures (POISINDEX(R), 1993,Bergdahl and Jarvholm, 2003). Once the tar cools, these types of exposures are no longer possible.Cooled tar is relatively non-toxic (POISINDEX(R), 1993).
The cooled tar in the Fort Wainwright tar sites is not in a form that would allow it to releasesignificant amount of vapors or coat the skin following dermal contact. Repeated, long termcontact with this material such that the tar could coat the skin is not likely given the limitedaccessability of the general public to this material. ATSDR noted during site visits that the tarmaterial will stick to certain items; however, individuals could walk across the tar and touch thetar without getting residual material on shoes or skin. Due to the climate, snow cover and heavyclothing would prevent direct contact with the material for months at a time. During the timewhen direct contact is possible; it is expected to be occasional and short term. Although thematerial is easily accessible, it is expected that people will not have continued, direct contact oftenenough to cause health effects. Therefore, ATSDR concludes the tar sites do not present a publichealth hazard to on-post employees, residents or visitors. However, ATSDR supports ADEC'sNFA request that all future actions involving the tar sites be coordinated with the SolidWaste/Pollution Prevention Program of ADEC.
References for Drinking Water
Agency for Toxic Substances and Disease Registry (ATSDR). 2001. Toxicological Profile for 1-2-Dichloroethane (Update). Atlanta: U.S. Department of Health and Human Services.
U.S. Environmental Protection Agency (EPA). 1996. Proposed Guidelines for Carcinogen RiskAssessment. Federal Register. Vol. 61, No. 79. April 23, 1996.
EPA. 1997. Exposure Factors Handbook, Volumes 1 and 2. Office of Research and Development.National Center for Environmental Assessment. Washington, DC: U.S. Environmental ProtectionAgency.( EPA/600/P-95/002Fa)
References for Emissions from the Coal-Fired Power Plant
CH2M Hill. 1994. USACE-AK. Site Release Investigation Report, Delivery Order 3, FortWainwright, Alaska. Anchorage, AK: CH2M Hill.
Clean Air Task Force. 2002. Clean Air Task Force Fact Sheet; Maryland Kids Facts. Accessed onJune 26, 2003, at:http://www.catf.us/publications/fact_sheets/children_at_risk/Maryland_Kids_Facts.pdf .
Dresher W. 1976. Arizona's Energy Resources and Development. In Energy in Perspective: AnOrientation Conference for Educations, ERDA Conf-760677, Ed. McKlveen JW. Tempe, AZ:ERDA. Accessed on June 26, 2003, at:http://www.eas.asu.edu/~holbert/eee463/ARIZONA.HTML .
U.S. Department of Energy. 2002a. Electricity Generation. Washington: U.S. Department ofEnergy. Accessed on June 26, 2003 at:http://www.eia.doe.gov/cneaf/electricity/page/prim2/chapter3.html .
U.S. Department of Energy.2002b. Electric Power Industry Overview, Environmental Aspects.Washington: U.S. Department of Energy. Accessed on June 26, 2003, at:http://www.eia.doe.gov/cneaf/electricity/page/prim2/toc2.html .
EPA. 1996. Record of Decision. Washington: U.S. Environmental Protection Agency.(EPA/ROD/R10-96/150) Washington: U.S. Environmental Protection Agency.
EPA.1998. Study of Hazardous Air Pollutant Emission from Electric Utility Steam GeneratingUnits - Final Report to Congress; Volume 1. Washington: U.S. Environmental Protection Agency.Executive Summary accessed on June 26, 2003, at:http://www.epa.gov/ttn/oarpg/t3/meta/m28497.html .
EPA .1999. Press Release: Coal-Fired Power Plant at Fort Wainwright Issued EPA Notice ofClean Air Act Violation. Washington: U.S. Environmental Protection Agency.
EPA. 2000. Press Release: EPA Decides Mercury Emissions from Pow+er Plants Must BeReduced. Washington: U.S. Environmental Protection Agency.
EPA. 2002a. Superfund National Priorities List Assessment Program (SNAP) Database. Accessedon June 26, 2003, at http://www.epa.gov/superfund/sites/npl/nar1232.htm .
Katoh, N. 2002. Determination of Polycyclic Aromatic Hydrocarbons in Coal Combustion GasUsing High Performance Liquid Chromatography. Tetsu to Hagane - Journal of the Iron and SteelInstitute of Japan. 88(11):741-6.
Laxen D, Wilson P, Longhurst J,et al. 2002. Compilation of New Roadside Monitoring DataObtained by Local Authorities as Part of the Review and Assessment Process. Air QualityConsultants Ltd., Bristoal, United Kingdom. Accessed on June 26, 2003, at:http://www.defra.gov.uk/environment/airquality/laqm/monitor/pdf/air_roadside_monitor.pdf .
Llorens JF, Fernandez-Turiel JL, Querol X . 2001. The Fate of Trace Elements in a Large Coal-Fired Power Plant. Environmental Geology 40(4-5): 409-16.
Maryland Department of Natural Resources. 1999. Power Plant Update. Volume 5, No. 4.Accessed on June 26, 2003, at:http://www.esm.versar.com/pprp/updates/sum99/mercury/mercury.html .
Mastral AM, Calle MS, Garcia T, Lopez JM. 2001. Benzo(a)pyrene, Benzo(a)anthracene, andDibenzo(a,h)anthracene Emissions from Coal and Waste Tire Energy Generation at AtmosphericFluidized Bed Combustion (AFBC). Environmental Science and Technology. 35(13):2645-9.
Meij R, Vredenbregt LHJ, Winkel HT. 2002. The Fate and Behavior of Mercury in Coal-FiredPower Plants. Journal of the Air and Waste Management Association. 52(8):912-7
Nielsen MT, and Livbjerg H . 2002. Formation and Emission of Fine Particles from Two Coal-Fired Power Plants. Combustion Science and Technology. 174(2):79-113.
Ramadan Z, Song XH, Hopke PK. 2000. Identification of Sources of Phoenix Aerosol by PositiveMatrix Factorization. Journal of the Air and Waste Management Association 50(8):1308-20.
Revuelta CC, Santiago AD, Vazquez JAR. 1999. Characterization of Polycyclic AromaticHydrocarbons in Emissions from Coal-Fired Power Plants: The Influence of OperationParameters. Environmental Technology 20(1): 61.
Suarez AE and Ondov JM. 2002. Ambient Aerosol Concentrations of Elements Resolved by Sizeand by Source: Contributions of Some Cytokine-active Metals from Coal- and Oil-Fired PowerPlants. Energy and Fuels 16(3):562-8.
References for Coal Ash
ADEC. 1996. Air Monitoring in the Lemon Creek Valley. Fairbanks, AK: Alaska Department of Environmental Conservation. Accessed on June 26, 2003, at: http://www.state.ak.us/local/akpages/ENV.CONSERV/dawq/aqi/lcvalley.htm .
U.S. Army Fort Wainwright. 1992. APVR-FW-DE-ENV. Memorandum for Record. Use of CoalAsh on Fort Wainwright Roads. Fairbanks, AK: U.S. Army.
ATSDR. 1999. ATSDR Toxicological Profile for Mercury. Atlanta: U.S. Department of Healthand Human Services.
Bhumbla, D. 1996. Coal Ash for Reclamation. West Virginia University, Division of Plant andSoil Science. Morgantown, WV: West Virginia University. Accessed on June 26, 2003, at: http://www.wvu.edu/~research/coalash.html.
CPM Inc. 2000. Bottom Ash. Combustion Products Management Inc. Ithaca, NY: CombustionProducts Management, Inc. Accessed on June 26, 2003, at:http://www.cpmash.com/ash/bottomash.html .
Department of Transportation. 2002. Utilization of Recycled Material in Illinois HighwayConstruction, Bottom Ash. Washington: Department of Transportation, Federal HighwayAdministration. Accessed on June 26, 2003, at: http://www.fhwa.dot.gov/pavement/recbash.htm .
EPA. 1987. Representative Metal Content of Typical Soils, in: A Compendium of Super FundField Operations Methods, Volume 2. Washington: U.S. Environmental Protection Agency.(EPA/540/P-87/001B)
Fitz DR. 1998. Evaluation of Street Sweeping as a PM10 Control Method. Final Report to theSouth Coast Air Quality Management District under Contract 96018, January. 98-AP-RT4H-005-FR. Riverside, CA: Center for Environmental Research and Technology. Accessed on June 26,2003, at: http://www.cert.ucr.edu/research/project.asp?project=41 .
Flygt. 2003. Pumping Abrasive bottom Ash Slurry with no Wear or Repairs. ITT Flygt.Stockholm, Sweden. Accessed on January 30, 2003, at http://www.flygt.com/37499.asp .
Ford 2003. 2003 Body Builder Layout Book, F-150 Model Lineup. Accessed on January 30, 2003, at http://www.fleet.ford.com/truckbbas/non-html/2003/bb_pdf/7-8.pdf .
Kalyoncu RS. 2001. Coal Combustion Products. U.S. Geological Survey Minerals Yearbook.Reston, VA: U.S. Geological Survey.
Laxen, D, et al. 2002. Compilation of New Roadside Monitoring Data Obtained by LocalAuthorities as Part of the Review and Assessment Process. Air Quality Consultants Ltd, 12 StOswarlds Road, Bristoal BS6 7HT, UK. Bristol, UK: Air Quality Consultants, Ltd. Accessed on June 26, 2003, at:http://www.defra.gov.uk/environment/airquality/laqm/monitor/pdf/air_roadside_monitor.pdf .
Newcastle City Council. 2000. Review and Assessment of Air Quality in the City of Newcastleupon Tyne. Chapter 6, Review and Assessment of PM10. Environment Enterprise and CultureDirectorate, Newcastle City Council, United Kingdom. Newcastle upon Tyne, UK: NewcastleCity Council, Environmental Enterprise and Culture Directoriate. Accessed on June 26, 2003, at: http://www.newcastle.gov.uk/airquality/chapter6.pdf
TFHRC. 2003. Coal Bottom Ash/Boiler Slag. Turner-Fairbank Highway Research Center, USDepartment of Transportation. Accessed on January 30, 2003, athttp://www.tfhrc.gov/hnr20/recycle/waste/cbabs1.htm .
References for the Tar Sites
Bergdahl IA and Jarvholm B. 2003. Cancer Morbidity in Swedish Asphalt Workers. AmericanJournal of Industrial Medicine 43(1):104-8.
Fort Wainwright. 1991. Groundwater Monitoring Well Location Map.
USACE-AK. 1992. Memoranda from Delwyn F. Thomas, Chief, Geotechnical Branch, toCENPA-EN-EE-AI, concerning Chemical Analyses Results, Tar Pits I and II. 7 October 1992 and15 October 1992.
Hazardous Substances Data Bank (HSDB)Accessed on Accessed on June 26, 2003, at http://csi.micromedex.com/fraMain.asp?Mnu=0 .
Kimmell TA. 1999. Original Purpose of the Toxicity Characteristic Leaching Procedure (TCLP).Presentation to US EPA 1999 Public Meeting, Development of New Waste Leaching Procedures.July 22-23, 1999.
NAPA. 2002. An Asphalt Plant in Your Community. National Asphalt Pavement AssociationAccessed on January 29, 2003, at http://www.hotmix.org/ .
National Library of Medicine. 2003. Hazardous Substances Data Bank. U.S. Department ofHealth and Human Services. Search results for 'asphalt' on January 29, 2003, at http://csi.micromedex.com/DATA/HS/HS5075B.htm/ .
NIOSH. 2000. Hazard Review, Health Effects of Occupational Exposure to Asphalt. Washington:U.S. Department of Health and Human Services (#2001-2110)
POISINDEX(R). 1993. Asphalt, HAZARDTEXT (R) Hazard Management. Database search for'asphalt' on January 29. 2003, at http://csi.micromedex.com/DATA/DT/DT317.HTM?Top=Yes
Randem BG, et al. 2003a. Cancer Incidence Among Male Norwegian Asphalt Workers. AmericanJournal of Industrial Medicine 43(1):88-95.
Randem BG, et al. Mortality from Non-Malignant Diseases Among Male Norwegian AsphaltWorkers. American Journal of Industrial Medicine 43(1):96-103.
Stucker I, et al. 2003. Cohort Mortality Study Among French Asphalt Workers. American Journalof Industrial Medicine 43(1):58-68.
USACE-AK. 1995. U.S. Army Corps of Engineers Alaska District, 1995; No Further Action Site Summaries, Operable Unit 1-5, Fort Wainwright, Alaska: U.S. Army Corps of Engineers.
ATSDR received comments from two different sources for the Public Comment Public HealthAssessment for Fort Wainwright. All of the comments provided clarification of, or editorialchanges to the text. ATSDR incorporated those comments into the text.
ATSDR did receive one comment from a community member, it is addressed below.
A number of years ago, I believe in 1978 I was employed on the army base. One day, we weredirected to load up a huge flatbed truck that contained probably over 50 and less than 100 50gallon drums containing unknown substances. We then pick axed them open and pitched themover the edge of a hill on the seemingly deserted part of the base. At the time, being just a youngperson I just did it. Now I'm concerned about the environmental damage caused by thosechemicals and if my health could be affected by exposure to those chemicals.
The Environmental Office at Fort Wainwright, in coordination with the Alaska Department ofEnvironmental Conservation and the EPA, are continually working to characterize and remediatehistoric dumping sites on Fort Wainwright. Based on the information provided, I can't be certain ifthe site you described was covered in the public health assessment.
ATSDR discussed your concerns with the Fort Wainwright Environmental Office. We have beenassured that if you contact them, they will be able to go through their records and maps with you.They will be able to identify if the area you describe has been investigated and if so, the results ofthe investigation. If the site has been investigated, they will likely know the types of chemicalsthat were disposed of and what your occupational exposure may have been. If the site has not yetbeen investigated they will be able to use your information to evaluate if future environmentalinvestigations need to be considered.