PUBLIC HEALTH ASSESSMENT
EASTERN SURPLUS COMPANY SITE
MEDDYBEMPS, WASHINGTON COUNTY, MAINE
|August 1946||HarrySmith, Sr.||Acquired property.|
|October 1946||Smith||Began storing equipment and materials for Eastern Surplus.|
|Before 1966||Smith||Generated electricity with hydroelectric power unit on the Dennys River.|
|Around 1973||Smith||Stopped receiving surplus and salvage goods.|
|Before ~1976||Smith||Ran a military surplus business in concrete block building in southeastcorner|
|Mid 1970s||Interviewee||Reported that a fire possibly involving calcium carbide occurred near therear of the site.|
|October 1985||MEDEP||Conducted a site visit in response to complaints. Soil samples were found tocontain PCBs.|
|October 1985||MEDEP||Conducted an initial site visit and recommended emergency actions.|
|December 1985||MEDEP||Initiated clean-up.|
|December 1985||MEDEP||Designated the site as an Uncontrolled Hazardous Substance Site.|
|December 1985-April 1986||MEDEP||Conducted source sampling and clean-up.|
|1986- 1990||EPA &DOD||Sampled and removed hazardous materials: drums, cans, gas cylinders,transformers. Source sampling coordinated by MEDEP & EPA.|
|January 1986||MEDEP||Completed Potential Hazardous Waste Site Preliminary Assessment. Reportstated that the site posed a threat to the environment and public health.Immediately initiated emergency clean-up and removal measures anderected a lockable security fence.|
|April 1986||MEDEP||Removed additional ammunition, 4,600 gallons waste oils, 2,400 gallonsPCBs, and 117 transformers. Then requested federal assistance.|
|May 1986||MEDEP||Suspended removal, having erected a security fence.|
|August 1986||MEDEP &USFWS||Collected surface water, sediment, soil, and fish samples from site, DennysRiver, and Meddybemps Lake.|
|November 1986||EPA||Approved Immediate Removal Action.|
|December 1986||EPA||Began air monitoring. Sampled 1 calcium carbide container. Packed 127 55-gallon drums.|
|May 1987||EPA||Began sampling 55-gallon drums and sampled fibrous material from metaltubes.|
|June 1987||EPA||Began identifying and sampling 5-gallon cans.|
|November 1987||EPA||Sampled several waste streams.|
|April 1988||EPA FITcontractor||Installed groundwater monitoring wells. Sampled and analyzed soil,sediment, groundwater, and surface water. Removed over 100 55-gallondrums, 168 100-pound cans of calcium carbide, and 390 5-gallon cans fromthe site. Constructed crushing pad.|
|May 1988||EPA||Removed 70 5-gallon cans, 60 lab packs, and an 85-gallon drum of wasteoil.|
|June 1988||EPA||Removed 10 cubic yards of asbestos-containing material, 38 55-gallondrums, and 21 5-gallon cans.|
|July 1988-December 1988||DOD||Performed site preparation, staging, venting, incineration, off site shipmentof gas cylinders.|
|September 1988||DOD||Sampled and analyzed 17 private wells within 0.5 miles for VOCs.|
|April 1989-July 1990||DOD||Removed gas cylinders and 55-gallon drums.|
|October 1989||EPA||Removed 7 commercial compressed gas cylinders. One cylinder of nitricoxide vented on site. Conducted air monitoring.|
|July 1990||EPA||Removed drums of waste, PCB solids, arsenate of calcium, electrical parts,waste stream waste, and empty drums.|
|January 1995||MEDEP||Completed final Hazard Ranking System Package, giving a score of 50.|
|June 1996||EPA||Placed the site on NPL.|
|August 1996||EPA||Initiated RI/FS, including: soil borings, well installation, sampling andscreening of soil, groundwater, private well, surface water, sediment, andbiota.|
|September 1996-October 1996||Weston||Sampled 10 surface water and 40 sediment locations.|
|September 1996||Weston||Took 32 initial analytical soil samples. Sampled 4 monitoring wells and 26private wells.|
|September 1996-October 1996||Weston||Sampled 5 private wells.|
|October 1996||OestAssociates||Completed topographic surveys.|
|1996-1998||OestAssociates||Completed additional surveys.|
|November 1996||USGS||Installed 19 monitoring wells.|
|October 1996||Weston||Collected > 500 screening soil samples, 60 additional CLP confirmationsamples, 20 dioxin samples, and 40 sediment samples from Dennys Riverand Meddybemps Lake.|
|December 1996||Weston||Sampled 23 on-site monitoring wells and 1 private well.|
|April 1997||USGS||Took 10 samples from soil borings.|
|May 1997||USGS||Installed 4 monitoring wells and converted 1 private well to be a monitoringwell.|
|June 1997||Weston||Collected 12 soil sampled from the VOC hot spot.|
|June 1997||EPA||Sampled 2 soil gas canister, 28 on-site and off-site groundwater monitoringwells. Performed ambient air survey. Collected soil samples form QuadrantII.|
|June 1997||Weston||Sampled 26 monitoring wells.|
|June 1997, October 1997||Weston||Sampled 4 private wells in June and again in October.|
|June 1997||EPA||Installed and sampled 8 ambient air sampler stations while Weston wasinvestigating the VOC hot spot area.|
|September 1997||USFWS/EPA||Collected fish and mussels screening samples.|
|October 1997||Weston||Collected 10 surface water, 20 sediment, and 20 monitoring well samples.|
|October 1997||TTNUS||Conducted site preparation activities.|
|October 1997||Weston||Collected 16 samples from previously inaccessible areas, other areas, andbackground.|
|October 1997-November 1997||TTNUS||Performed a thermal desorption treatability test--1 soil sample taken fromVOC hot spot.|
|October 1997-November 1997||TTNUS||Collected 3 grab samples of ooze and debris, test pit samples, 67 screeningsamples from soil boring of which 32 analyzed, 14 grab samples of "on-sitebackground" areas and in test area.|
|October 1997||EPA||Sampled 5 ambient air stations during VOC hot spot excavations.Conducted treatability/field investigation for vapor extraction. Took 14 soilborings, of which, 6 were converted to monitoring wells. Took 6 soilborings , of which, 3 were converted to monitoring wells. Sampled 8monitoring wells.|
|November 1997||EPA||Sampled 5 ambient air stations during soil vapor extraction test. Installed 7groundwater monitoring wells and vapor extractions system. Collected soilsamples.|
|December 1997||TTNUS||Performed aquifer test and well evaluation to test hydraulic connection.Sampled 2 monitoring wells.|
|May 1998||USGS||Installed 1 monitoring well.|
|June 1998||TTNUS||Collected 6 surface water and 7 sediment samples from Dennys River,Meddybemps Lake, and Mill Pond. Characterized building.|
|June 1998||TTNUS||Sampled 36 monitoring wells and 4 private wells.|
|August 1998-October 1998||TTNUS||Conducted soil sampling to delineate hot spots, analyze newly accessibleareas, and confirm previous elevated metals. Destroyed unexplodedordnance (UXO).|
|August 1998||TTNUS||Inventory of ecological resources.|
|September 1998-October 1998||TTNUS||Analyzed > 850 soil samples by onsite mobile laboratory, 25 werebackground.|
|October 1998||USACE||Demolished wood frame residence.|
|October 1998-November 1998||USACE/EPA||Removed concrete block building and miscellaneous waste. Extendedperimeter fence|
|October 1998-November 1998||USACE||Under agreement with EPA performed Non-Time-Critical Removal Action:demolition and disposal of wood frame and concrete building. Soilsampling, water removal, characterizing and removing drums, cylinders,surveying bank of Dennys River, found elevated PCB and arsenic beneathconcrete building.|
|October 1998||TTNUS||Installed 4 small diameter monitoring wells.|
|October 1998||USArmyEOD||Assisted Army unit from Ft. Monmouth NJ on a site visit to remove UXO.|
|November 1998||TTNUS||Sampled 22 monitoring wells and 4 private wells.|
|November-December 1998||EPA||Installed extraction wells.|
|January-February 1999||EPA||Sampled groundwater.|
|May 1999||EPA||Conducted archeological survey.|
|June 1999||EPA||Installed bedrock extractions wells.|
|June 1999||USACE||Began additional excavation to remove soil.|
|August 1999||EPA||Proposed long-term cleanup plan.|
|Autumn 1999||EPA||Completed soil removal.|
|CLP||Contract Laboratory Program|
|DOD||Department of Defense|
|EOD||Explosive Ordnance Disposal|
|EPA||U.S. Environmental Protection Agency|
|FIT||Field Investigation Team|
|MEDEP||Maine Department of Environmental Protection|
|TTNUS||TetraTech NUS, Inc.|
|USACE||U.S. Army Corps of Engineers|
|USFWS||U.S. Fish and Wildlife Service|
|USGS||U.S. Geological Survey|
|VOC||Volatile organic compound|
Source: 1, 2
In preparing this report, the Agency for Toxic Substances and Disease Registry (ATSDR)reviewed and evaluated information provided in the referenced documents. Documents preparedunder the Superfund program must meet specific standards for adequate quality assurance andcontrol measures for chain-of-custody procedures, laboratory procedures, and data reporting.
The groundwater, private well, surface soil, surface water, sediment, air, fish, and shellfish datapresented in the Remedial Investigation (1) were validated to assure that samples were analyzedin accordance with quality control requirements stipulated by EPA for Superfund sites. Nosignificant quality assurance/quality control problems were noted in file data.
Human Exposure Pathway Evaluation and the use of ATSDR Comparison Values
ATSDR assesses a site by evaluating the level of exposure in potential or completed exposurepathways. An exposure pathway is the way chemicals may enter a person's body to cause ahealth effect. It includes all the steps between the release of a chemical and the populationexposed: (1) a chemical release source, (2) chemical movement, (3) a place where people cancome into contact with the chemical, (4) a route of human exposure, and (5) a population thatcould be exposed. In this assessment, ATSDR evaluates contaminants found in different mediathat people living near the site may consume or come into contact with.
Data evaluators use comparison values (CVs), which are screening tools only used to evaluateenvironmental data that is relevant to the exposure pathways. CVs are concentrations ofcontaminants that are considered to be safe levels of exposure. CVs used in this documentinclude ATSDR's environmental media evaluation guide (EMEG) and cancer risk evaluationguide (CREG), as well as the U.S. Environmental Protection Agency's (EPA) risk-basedconcentrations (RBCs). CVs are derived from available health guidelines, such as ATSDR'sminimal risk levels (MRLs) and EPA's reference doses or cancer slope factors.
The derivation of a CV uses conservative exposure assumptions, resulting in values that aremuch lower than exposure concentrations observed to cause adverse health effects; thus, insuringthe CVs are protective of public health in essentially all exposure situations. That is, if theconcentrations in the exposure medium are less than the CV, the exposures are not of healthconcern and no further analysis of the pathway is required. However, while concentrations belowthe CV are not expected to lead to any observable health effect, it should not be inferred that aconcentration greater than the CV will necessarily lead to adverse effects. Depending on site-specific environmental exposure factors (for example, duration of exposure) and activities ofpeople that result in exposure (time spent in area of contamination), exposure to levels above theCV may or may not lead to a health effect. Therefore, ATSDR's CVs cannot be used to predictthe occurrence of adverse health effects.
The CVs used in this evaluation are defined as follows:
Cancer Risk Evaluation Guides (CREGs) are concentrations of a contaminant in air, water, ofsoil which, assuming default values for (adult) body weight and intake rates, would correspond toexposure doses estimated to produce no more than one excess cancer in a million personsexposed. CREGs are calculated from EPA's cancer slope factors and therefore reflect estimatesof "risk" based on the assumption of zero threshold and lifetime exposure. It should be noted,however, that the true risk is unknown and could be as low as zero.
The CREG is used to evaluate potential cancer effects. The CREG is the most conservative ofCVs because it assumes that no threshold exists for the effects of chemical carcinogens. Theresulting CREG can therefore often be below typical background levels and common detectionlimits. CREGs do not define levels of actual hazard (e.g., a 1-in-a-million "risk" level) andcannot be used to predict actual cancer incidence under specified conditions of exposure. Asstated in EPA's 1986 Cancer Risk Assessment Guidelines, "the true risk is unknown and may beas low as zero."
Environmental Media Evaluation Guides (EMEGs) are concentrations of a contaminant inair, water, or soil that are calculated from ATSDR's MRLs for acute, intermediate, or chronicexposure by factoring in default body weights and ingestion rates for adults and children (and, inthe case of soil, pica children). The MRLs on which the EMEGs are based are ATSDR'sestimates of daily human exposure doses of a contaminant (expressed in milligrams orcontaminant per kilogram of body weight per day [mg/kg/day]) that ATSDR considers unlikelyto be associated with any appreciable risk of harmful noncancer effects over a specified durationof exposure. MRLs are calculated using data from human and animal studies and, like theEMEGs derived from them, are reported for acute (< 14 days), intermediate (15-364 days), andchronic (> 365 days) exposures. MRLs are published in ATSDR Toxicological Profiles forspecific chemicals, but the EMEGs are not.
Reference Media Evaluation Guides (RMEGs) are derived from EPA's oral reference doses(RfDs). The RMEG represents the concentration in water or soil at which daily human exposureis unlikely to result in adverse noncarcinogenic effects.
Lifetime Health Advisories for Drinking Water (LTHA) are derived by EPA based oninformation about the toxicity of a contaminant. LTHAs are considered the concentration of acontaminant in drinking water that is not expected to cause adverse noncancer health effects for alifetime of exposure in drinking water.
Maximum Contaminant Levels (MCL) are drinking water standards established by EPA. Theyare the maximum permissible level of a contaminant in water that is delivered to the free-flowingoutlet. MCLs are considered protective of public health over a lifetime (70 years) for peopleconsuming 2 liters of water per day.
Risk-Based Concentrations (RBCs) were developed by EPA Region III. RBCs for tap water,air, and soil were derived using EPA's reference doses and cancer slope factors combined withstandard exposure scenarios, such as ingestion of 2 liters of water per day, over a 70-year lifespan. RBCs are contaminant concentrations that are not expected to cause adverse health effectsover long-term exposures.
Soil Screening Levels (SSL) were derived by EPA for nation-wide application to sites used forresidential areas. SSLs are estimates of contaminant concentrations that would be expected to bewithout noncancer health effects over a specified duration of exposure or to cause no more thanone excess cancer in a million (10-6) persons exposed over a 70-year life span.
Selecting Contaminants for Further Evaluation
Contaminants selected for further evaluation are the site-specific chemical substances that thehealth assessor identifies for further evaluation of potential health effects. Identifying thesecontaminants is a process that requires the assessor to examine contaminant concentrations at thesite, the quality of environmental sampling data, and the potential for human exposure. Athorough review of each of these issues is required to accurately select contaminants in the site-specific human exposure pathway. The following text describes the selection process.
In the first step of the contaminant selection process, the maximum contaminant concentrationsare compared directly to CVs. ATSDR considers site-specific exposure factors to ensureselection of appropriate CVs. If the maximum concentration reported for a contaminant was lessthan the CV, ATSDR concluded that exposure to that chemical was not of public health concern;therefore, no further data review was required for that contaminant. However, if the maximumconcentration was greater than the CV, the contaminant was selected for additional data review.In addition, any contaminants detected that did not have relevant CVs were also selected foradditional data review.
CVs have not been developed for some contaminants, and, based on new scientific informationother CVs may be determined to be inappropriate for the specific type of exposure. In thosecases, the contaminants are included as contaminants of concern if current scientific informationindicates exposure to those contaminants may be of public health concern.
The next step of the process requires a more in-depth review of data for each of the contaminantsselected. Factors used in the selection process included the number of samples with detectionsabove the minimum detection limit, the number of samples with detections above an acute orchronic health comparison value, and the potential for exposure at the monitoring location.
- 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.
- A group of diseases which occur when cells in the body become abnormal and grow, or multiply, out of control
- 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.
- 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 chemical 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.
- 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).
- Lowest Observed Adverse Effect Level. The lowest dose of a chemical in a study, or group of studies, that has caused harmful health effects in people or animals.
- 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).
- Safety Factor:
- Also called Uncertainty Factor. When scientists don't have enough information to decide if an exposure will cause harm to people, they use "safety factors" and formulas in place of the information that is not known. These factors and formulas can help determine the amount of a chemical that is not likely to cause harm to people.
- 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.
- Special 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.
- A branch of the math process of collecting, looking at, and summarizing data or information.
- A way to collect information or data from a group of people (population). Surveys can be done by phone, mail, or in person. ATSDR cannot do surveys of more than nine people without approval from the U.S. Department of Health and Human Services.
- 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.
- 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.
Private drinking water well sampling data identified arsenic from 1.2 to 40.8 parts per billion[ppb] in private wells near the Eastern Surplus site. To evaluate the likelihood, if any, thatarsenic in these private wells is associated with adverse health effects, ATSDR derived exposuredoses and evaluated the weight of evidence for arsenic toxicity. Deriving exposure doses requiresevaluation of contaminant concentrations and length of exposures. Together, these factors helpinfluence the individual's physiological response to chemical contaminant exposure and potentialoutcomes. In the absence of complete exposure-specific information, ATSDR applied severalconservative exposure assumptions to define site-specific exposures as accurately as possible forthe private wells users.
ATSDR derived exposure doses using the following assumptions about a person's use of privatewell water as drinking water:
- ATSDR estimates that an adult drinks 2 liters and a child drinks 1 liter of water a day and that all drinking water comes from private wells.
- The exposure frequency, or number of exposure events per year, was assumed to be 365 days per year, based on a 7-days-a-week exposure over 52 week per year.
- The duration of exposure is assumed to have occurred over a 30-year period for adults. This value is the 90% upper-bound limit for residency at a single residence (15). This estimate most likely overestimates the actual duration of exposure, which is likely less than 30 years. For a child, ATSDR used a 6 year exposure duration.
ATSDR compared the estimated doses to standard toxicity values, including ATSDR's minimalrisk levels (MRLs) and EPA's reference doses (RfDs). The chronic MRLs and RfDs areestimates of daily human exposure to a substance that are unlikely to result in adverse noncancereffects over a specified duration. To be very protective of human health, MRLs and RfDs havebuilt in "uncertainty" or "safety" factors that make them much lower than levels at which healtheffects have been observed. Therefore, if an exposure dose is much higher than the MRL or RfD,it does not necessarily follow that adverse health effects will occur. ATSDR also compared dosesto the cancer effect level (CEL). The CEL is the dose at which tumors, or cancer effects, are seenin laboratory or epidemiology studies.
For noncancer effects, ATSDR found that exposures to the maximum detected concentration ofarsenic (40.8 ppb) would result in a dose below the MRL/RfD for an adult. For cancer effects,ATSDR found that estimated exposures over 30 years would result in a dose below the CEL,which is based on a epidemiology study of people exposed to arsenic for over 45 years. Doses arejust slightly above the MRL/RfD for a child. Even though the estimated doses for a child slightlyexceed the MRL/RfD for arsenic, we do not expect that a child drinking water at these taps willexperience health effects. First, ATSDR assumed that a child was exposed for an extended periodof time to the highest level of arsenic measured in the private wells. This provided a veryconservative estimate of potential exposure because a child probably did not drink from the samewell or drink the highest levels of arsenic for this estimated length of time. Second, as noted, theMRL/RfD are set much lower than levels at which health effects have been observed.
ATSDR also reviewed available scientific literature on arsenic to evaluate whether adversehealth effects would be likely to occur at the reported concentrations or at the estimated doses.Several epidemiologic investigations suggest an association between arsenic (inorganic) and awide variety of adverse health effects in humans, but at doses higher than those resulting fromdrinking the maximum arsenic concentrations detected in the private wells. Symptoms of chronicoral exposure appear to be skin problems (e.g., hyperkeratosis, hyperpigmentation), neurologicaleffects, cardiovascular problems, and gastrointestinal irritations (e.g., vomiting, abdominal pain).Health effects from prolonged (e.g., 45 years) exposure of arsenic have been detected at doses of0.014 milligrams contaminant per kilogram body weight per day (mg/kg/day) and higher(ATSDR 1998). The estimated exposure doses for a person drinking private well water near theEastern Surplus site for a 45 year period is more than 10 times lower than this dose.
ATSDR looked at potential cancer threats posed by arsenic at the measured concentrations. EPAhas classified arsenic as a human carcinogen based on data provided by epidemiologic studies.The basis for classifying arsenic as a human carcinogen are results of multiple epidemiologicstudies. One of the most cited studies is a Taiwanese study in which the lowest exposure levelsassociated with the onset of cancer (skin) were observed in people drinking water containing 170to 800 ppb arsenic for a 45-year exposure period (16). Although the study demonstrated anassociation between arsenic in drinking water and skin cancer, the study failed to account for anumber of complicating factors, including exposure to other nonwater sources of arsenic, geneticsusceptibility to arsenic, and poor nutritional status of the exposed population. Furthermore,arsenic exposure may have been underestimated in the study, possibly leading to anoverestimation of the actual risk. These weakness and uncertainties may limit the study'susefulness in evaluating cancer risk for residents drinking water containing arsenic near theEastern Surplus site.
Furthermore, various studies indicate that at low level exposures, arsenic compounds aredetoxified (or metabolized)--that is, changed into less harmful forms--and then excreted in theurine. At higher levels of exposures, our bodies' capacity to detoxify arsenic may be exceeded.Certain studies suggest that the dose at which this happens is somewhere between 0.25 and 0.5mg/kg/day, which is much higher than the dose level estimated here (16). When our body'scapacity to detoxify is exceeded, blood levels of arsenic increase and adverse health effects mayoccur. This appears to be true for cancer and noncancer effects. At lower doses, scientistscontinue to study the relevance between metabolism and toxicity.
At EPA's request, a special subcommittee of the National Research Council (NRC) reviewed thearsenic toxicity data base and evaluated the scientific basis of EPA's risk assessment for arsenicin drinking water (17). They concluded:
- Sufficient evidence exists from human epidemiologic studies (Taiwan, Chile, and Argentina) that chronic ingestion of water containing several hundred parts per billion of arsenic causes skin, bladder, and lung cancer. Only very little information is available to address cancer risk at lower concentrations. The subcommittee has therefore recommended further evaluation of the dose-response relationship between arsenic and cancer at lower doses.
- Noncancer effects (skin, cardiovascular, and neurologic effects) were observed at chronic exposures of 0.01 mg/kg/day and higher. No developmental or reproductive effects were demonstrated in humans, although arsenic passes through the placenta. In addition to characterizing the dose-response relationship at low doses, the subcommittee recommends further study on skin effects, cardiovascular and cerebrovascular diseases, diabetes mellitus, and reproductive effects.
- More information is needed on the mode of action by which arsenic causes adverse effects and cancer. For example, current information suggests that arsenic causes cancer by "inducing chromosomal abnormalities without interacting directly with DNA." If this is true, the dose-response curve would show sublinear characteristics in the low-dose range.
There is sufficient evidence to suggest that arsenic causes adverse health effects, includingcancer, but those levels are much higher than those measured in the private wells. Whilescientists are still uncertain about the health effects, if any, of long-term, low level exposure toarsenic in drinking water, enough evidence exists to suggest that arsenic is tolerated by humans atlow doses. Given this information, ATSDR does not believe that arsenic at the levels measuredin the private wells near the Eastern Surplus site are high enough to cause adverse health effectsor cancer.