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PUBLIC HEALTH ASSESSMENT

CALLAHAN MINING CORPORATION
BROOKSVILLE (CAPE ROSIER), HANCOCK COUNTY, MAINE


APPENDIX A: EXPLANATION OF EVALUATION PROCESS

Screening Process

In evaluating these data, ATSDR used comparison values (CVs) to determine which chemicalsto examine more closely. CVs are the contaminant concentrations found in a specific media (air,soil, or water) and are used to select contaminants for further evaluation. CVs incorporateassumptions of daily exposure to the chemical and a standard amount of air, water, and soil thatsomeone might inhale or ingest each day.

As health-based thresholds, CVs are set at a concentration below which no known or anticipatedadverse human health effects are expected to occur. Different CVs are developed for cancer andnoncancer health effects. Noncancer levels are based on valid toxicologic studies for a chemical,with appropriate safety factors included, and the assumption that small children (22 pounds) andadults are exposed every day. Cancer levels are based on a one-in-a -million excess cancer riskfor an adult eating contaminated soil or drinking contaminated water every day for 70 years. Forchemicals for which both cancer and noncancer levels exist, we use the lower level to beprotective. Exceeding a CV does not mean that health effects will occur, just that moreevaluation is needed.

CVs used in this document are listed below:

Environmental Media Evaluation Guides (EMEGs) are estimated contaminant concentrations ina media where noncarcinogenic health effects are unlikely. EMEGs are derived from the Agencyfor Toxic Substances and Disease Registry's (ATSDR) minimal risk level (MRL).

Cancer Risk Evaluation Guides (CREGs) are estimated contaminant concentrations that wouldbe expected to cause no more than one additional excess cancer in one million persons exposedover a lifetime. CREGs are calculated from the U.S. Environmental Protection Agency's (EPA)cancer slope factors (CSFs).

Reference Media Evaluation Guides (RMEGs) are estimated contaminant concentrations in amedia where noncarcinogenic health effects are unlikely. RMEGs are derived from EPA'sreference dose (RfD).

Preliminary Remediation Goals (PRGs) are the estimated contaminant concentrations in a mediawhere carcinogenic or noncarcinogenic health effects are unlikely. The PRGs used in this publichealth assessment were derived using provisional reference doses or CSFs calculated by EPA'sRegion 9 toxicologists.

Risk-Based Concentrations (RBCs) are the estimated contaminant concentrations at whichcarcinogenic and noncarcinogenic health effects are not expected to occur as a result ofexposure. The RBCs used in this public health assessment were derived using provisionalreference doses or CSFs calculated by EPA's Region 3 toxicologists.

EPA Action Levels (ALs) are the estimated contaminant concentrations in water of whichadditional evaluation is needed to determine whether action is required to eliminate or reduceexposure. Action levels can be based on mathematical models.

EPA Soil Screening Levels (SSLs) are estimated contaminant concentrations in soil at whichadditional evaluation is needed to determine if action is required to eliminate or reduce exposure.

Determination of Exposure Pathways

ATSDR identifies human exposure pathways by examining environmental and humancomponents that might lead to contact with COCs. A pathway analysis considers five principalelements: a source of contamination, transport through an environmental medium, a point ofexposure, a route of human exposure, and an exposed population. Completed exposure pathwaysare those for which the five elements are evident, and indicate that exposure to a contaminant hasoccurred in the past, is now occurring, or will occur in the future. Potential exposure pathwaysare those for which exposure seems possible, but one or more of the elements is not clearlydefined. Potential pathways indicate that exposure to a contaminant could have occurred in thepast, could be occurring now, or could occur in the future. It should be noted that theidentification of an exposure pathway does not imply that health effects will occur. Exposuresmight be, or might not be, substantive. Therefore, even if exposure has occurred, is nowoccurring, or is likely to occur in the future, human health effects might not result.

ATSDR reviewed site history, information on site activities, and the available sampling data. Onthe basis of this review, ATSDR identified numerous exposure pathways that warrantedconsideration. Additional information regarding the completed and potential exposure pathwaysidentified for the Callahan Mining Corporation site is provided in Appendix B of this publichealth assessment. Summaries of these pathways are discussed below.

Evaluation of Public Health Implications

The next step is to take those contaminants present at levels above the CVs and further identifywhich chemicals and exposure situations are likely to be a health hazard. Child and adultexposure doses are calculated for the site-specific exposure scenario, using our assumptions ofwho goes on the site and how often they contact the site contaminants. The exposure dose is theamount of a contaminant that gets into a person's body. Following is a brief explanation of howwe calculated the estimated exposure doses for the site.

Soil, Tailings, and Waste Rock Contaminant Ingestion

Exposure doses for ingestion of contaminants present in soil from the source areas werecalculated using the average concentration measured in the source areas, in milligrams perkilogram (mg/kg), or parts per million (ppm), multiplied by the soil ingestion rate for adults (100mg/day) or children (200 mg/day).

The multiplication product was divided by the average weight for an adult, 70 kg (154 pounds)or a 10-year old child, 36.3 kg (80 pounds). The resulting dose was then multiplied by a factor of104/365, because the exposure was assumed to occur on average of twice per week throughoutthe year.

Soil, Tailings, and Waste Rock Contaminant Inhalation of Fugitive Dust

For exposure to contaminants in source soil via inhalation of fugitive dust from source area soil,the average detected soil concentrations was multiplied by an inhalation rate and an exposuretime of 2 hours per day. An inhalation rate of 2.3 cubic meters per hour (m3/hour) for adults and1.74 m3/hour for children was assumed, based on moderate activity. The multiplication productwas divided by the average weight for an adult, 70 kg (154 pounds) or a 10-year old child, 36.3 kg (80 pounds). The resulting dose was then multiplied by a factor of 104/365, because theexposure was assumed to occur on average of twice per week throughout the year, as in the soilingestion calculation.

Surface Water Ingestion

Exposure doses for surface water ingestion were calculated using the average concentration for a surface water contaminant, in milligrams per liter (mg/L), multiplied by an incidental surface water ingestion rate of 0.02 liter/day for adults or 0.01 liter/day for children. These ingestion rates are 1/100th of the EPA default drinking water rates. The multiplication product was divided by the average weight for an adult (70 kg or 154 pounds), or for a 1-year old child (10 kg or 22 pounds). The resulting dose was then multiplied by a factor of 60/365, because the exposure was assumed to occur 5 days per week during 3 summer months of the year.

Sediment Ingestion

Exposure doses for ingestion of contaminants from the sediment were calculated using the average concentration measured in the sediment, in mg/kg or ppm, multiplied by 1/10th of the soil ingestion rate, 10 mg/day for adults or 20 mg/day for children. The multiplication product was divided by the average weight for an adult (70 kg or 154 pounds) or a 10-year-old child (36.3 kg or 80 pounds). The resulting dose was then multiplied by a factor of 60/365, because the exposure was assumed to occur 5 days per week during 3 summer months of the year.

Dermal (Skin) Exposure

In this public health assessment, we evaluated dermal exposure to source area soil, surface water, and sediment. Dermal absorption depends on numerous factors including the area of exposed skin, anatomic location of exposed skin, length of contact, concentration of chemical on skin, chemical-specific permeability, soil adherence, medium in which the chemical is applied, and skin condition and integrity. Because chemicals differ greatly in their potential to be absorbed through the skin, each chemical needs to be evaluated separately and is discussed as needed in the main body of the public health assessment. The assumed receptor body weights, exposure frequency, and exposure duration are the same as described in the above calculations of the ingestion route. The skin surface area and soil-to-skin adherence factors used in this public health assessment were taken from EPA's Exposure Factor Handbook. (4) Absorption factors and other chemical-specific factors were taken from the ATSDR Toxicological Profile for each specific chemical.

Ingestion of Biota (Mussels) from Goose Cove

Exposure doses for ingestion of mussels from Goose Cove were calculated using the maximumdetected concentration measured in mussel samples, in mg/kg or ppm, multiplied by averageingestion rates of 11.0 grams per day (g/day) and 5.6 g/day for adults and children, respectively.The calculated value was also multiplied by a conversion factor of 0.001 kilograms per gram.The multiplication product was divided by the average weight for an adult (70 kg or 154 pounds)or a child less than two years of age (16 kg or 35 pounds).

Noncancer Health Effects

The calculated exposure doses are then compared to an appropriate health guideline for thatchemical. Health guideline values are considered safe doses; that is, health effects are unlikelybelow this level. The health guideline value is based on valid toxicological studies for achemical, with appropriate safety factors built-in to account for human variation, animal-to-human differences, and/or the use of the lowest adverse effect level. For noncancer healtheffects, the following health guideline values are used.

Minimal Risk Level (MRLs) - Developed by ATSDR

An MRL is an estimate of daily human exposure - by a specified route and length of time - to adose 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. A list of MRLs can befound at http://www.atsdr.cdc.gov/mrls.html.

Reference Dose (RfD) - Developed by EPA

An RfD is an estimate, with safety factors built in, of the daily, life-time exposure of humanpopulations to a possible hazard that is not likely to cause noncancerous health effects. RfDs canbe found at http://www.epa.gov/iris .

If the estimated exposure dose for a chemical is less than the health guideline value, then theexposure is unlikely to cause a noncarcinogenic health effect in that specific situation. If theexposure dose for a chemical is greater than the health guideline, then the exposure dose iscompared to known toxicologic values for that chemical and is discussed in more detail in thepublic health assessment (see Discussion section). These toxicologic values are doses derivedfrom human and animal studies that are summarized in the ATSDR Toxicological Profiles. Adirect comparison of site-specific exposure and doses to study-derived exposures and doses thatcause adverse health effects is the basis for deciding whether health effects are likely or not.

Calculation of Risk of Carcinogenic Effects

The estimated risk of developing cancer resulting from exposure to the contaminants wascalculated by multiplying the site-specific adult exposure dose by EPA's corresponding CSF(which can be found at http://www.epa.gov/iris ). The results estimate the maximum increase inrisk of developing cancer after 70 years of exposure to the contaminant.

The actual risk of cancer is probably lower than the calculated number, which gives a worst-caseexcess cancer risk. The method used to calculate EPA's CSF assumes that high-dose animal datacan be used to estimate the risk for low dose exposures in humans. The method also assumes thatno safe level exists for exposure. Little experimental evidence exists to confirm or refute thosetwo assumptions. Lastly, the method computes the 95% upper bound for the risk, rather than theaverage risk, suggesting that the cancer risk is actually lower, perhaps by several orders ofmagnitude. (5)

Because of uncertainties involved in estimating carcinogenic risk, ATSDR employs a weight-of-evidence approach in evaluating all relevant data.(6) Therefore, the carcinogenic risk is describedin words (qualitatively) rather than giving a numerical risk estimate only. The numerical riskestimate must be considered in the context of the variables and assumptions involved in theirderivation and in the broader context of biomedical opinion, host factors, and actual exposureconditions. The actual parameters of environmental exposures must be given carefulconsideration in evaluating the assumptions and variables relating to both toxicity and exposure.


APPENDIX B:

EXPOSURE PATHWAYS FOR CALLAHAN MINING CORPORATION SITE
PATHWAY NAME ENVIRONMENTAL MEDIA & TRANSPORT MECHANISMS POINT OF EXPOSURE ROUTE OF EXPOSURE EXPOSURE POPULATION TIME NOTES COMPLETE?
Soil Erosion of waste to surface soils; redeposition of fugitive dust Site soils, residences nearby Incidental ingestion, inhalation, dermal exposure Nearby residents, fishers and shellfish collectors, trespassing teenagers and adults Past, present, future Population might include children 10 years and older. Y
Waste rock and tailings Waste rock and tailings piles on site; erosion dispersed Waste piles on site Incidental ingestion, inhalation, dermal exposure Site workers, trespassing teenagers and adults Past, present, future Population might include children 10 years and older. Y
Surface water Surface water runoff over wastes to bay; dissolution from underwater mine pit Water in Goose Pond and Goose Cove Incidental ingestion, inhalation, dermal exposure Fishers and shellfish collectors, recreational users of bay (children and adults) Past, present, future Population might include young children. Y
Sediments Deposition from surface water runoff into bay; underwater tailings Along shoreline in Goose Pond Incidental ingestion, dermal exposure Fishers and shellfish collectors, recreational users of bay (children and adults) Past, present, future Population might include young children. Y
Biota Bioaccumulation of contaminants from surface water and sediments into shellfish and fish Meal prepared using fish or shellfish from site Ingestion Fishers and shellfish collectors and their families; purchasers of local seafood Past, present, future Population might include young children Y
Well water Infiltration to groundwater Groundwater wells supplying drinking water taps Ingestion, inhalation, dermal exposure Residents and workers near the site Past, present, future Population might include young children N
Air Volatilization of contaminants; fugitive dust Groundwater wells supplying drinking water taps Inhalation, dermal exposure Residents and workers near the site Past, present, future Population might include young children N


APPENDIX C: PUBLIC COMMENTS RECEIVED

TheCallahan MiningCorporationPublic HealthAssessment wasavailable forpublic review andcomment fromDecember 16,2002 until March15, 2003, on theInternet and at theBrooksvilleCommunityCenter inBrooksville,Maine. Thepublic commentperiod wasannounced inlocal newspapers,and fact sheetsannouncing theavailability of thepublic healthassessment weremailed toresidents near thesite. The PHAwas also sent tofederal, state, andlocal officials.The findings ofthe PHA werepresented byATSDR staff at apublic meetingheld April 1, 2003in Brooksville,Maine, and publiccomments wereaccepted for anadditional 2weeks after themeeting. Thewritten publiccommentsreceived are listedand addressedbelow.

Comments fromAlbert E.Sandecki,Chairman of theHolbrook IslandSanctuaryCorporation:

Comment A1: Byway of a minorcorrection onpage 4. TheEasterly shore ofGoose Pond isbordered by theHolbrook IslandSanctuary StatePark. Nowmanaged by theState of Maine'sBureau of Parksand Lands, whichin turn isoverseen by ourtrust theHolbrook IslandSanctuaryCorporation.

Response: Thankyou for theclarification. Thedocument hasbeen modifiedaccordingly.

Comment A2:The ATSDRlisting ofCommunityHealth Concernson page 6 mightconsider addingthat commercialsoft shell clamharvesting hasbeen done withinGoose Pond, andscallop draggingalso has beenobserved for thepast two seasonswithin GooseCove. Ref: Noticeof this was givento LeslieMcVickar, EPA'sRemedial ProjectManager at theBoston offices ofEPA.

Response: Thisconcern has beenadded to thereferenced sectionof the document.

Comments fromDebbie Weeks,Ph.D., of theMaine MaritimeAcademy:

Comment B1:Most of thesamples were soilsamples fromwaste rock pile 2- this does notseem to berepresentativesampling. Thelack of dissolvedcontaminantmeasurementsmakes it difficultto interpret themobilization anddistribution ofthesecontaminants. Acase for episodicdissolution, re-suspension andmobilization ofthesecontaminants canbe made, asrainfall(especially acidrain) willcontinue to leachmetals. Tidalfluxes introducesaline, low-contaminantwater which willfurther aid in themobilization ofthe contaminants.These issuesshould beaddressed.

Response: Basedon the availabledata considered inthis PHA, a totalof twelve soilsamples werecollected from thetailings pond (2samples),separation mill(one sample), siteentrance (4samples), andoperational areas(5 samples).Additionally,samples werecollected fromtailings pond (5samples), tailingspile (3 samples),and waste rockpile (8 samples).Becausemaximum levelsof contaminantswere similar forthese materials,soil, tailings, andwaste rock wereconsidered to beone exposurepathway for thepurpose of thisPHA.

At the currenttime, data is notavailable tocompletelycharacterizecontamination atthe site. EPA hasproposed thecollection ofadditional data toadequatelyaddress thisexposurepathway, as partof the RemedialInvestigation.Additional datawill also beevaluated byATSDR, and theconclusions of thePHA will bemodified ifnecessary.

Comment B2:Only blue musselswere sampled,and it is unclearfrom where theywere taken. Ofthose taken, allwere far abovethe EPAscreening levelsfor all toxicmetals tested, andthe values forcopper, iron, leadand zinc show asignificantincrease inconcentrationcompared to datafrom the 70's and90's. This seemsto indicate anINCREASE inrelease of theseelements since themine closed, asthese musselstypically live only10-15 years.

Response:

While ATSDRconcludes that notenough musselsdata was availableto make adefinitive healthcall regarding fishand shellfishconsumption,limited musselsdata wasevaluated toprovide generalinformation forpotential healthimpacts fromconsumption ofmussels fromGoose Cove. Themost currentmussels data,collected fromGoose Cove in2001, wereevaluated as partof this PHA.Historical datawere notconsidered in thisevaluation due todata qualityconcerns.

As part of thisPHA, ATSDRfocuses on theevaluation ofhuman healtheffects associatedwith exposure anddoes not considerpotentialecologicalimpacts.Therefore,concentrations ofmetals in themussels sampleswere comparedwith EPA RegionIII Risk-BasedConcentrations(RBCs)developed forhumanconsumption offish and shellfish.Based on the data,only three metals(arsenic,cadmium, andiron) were foundto exceed theEPA Region IIIRBCs. No othermetals werefound to beelevated abovethe screeninglevel. This limitedevaluationindicated thathealth effectswould not likelyresult forindividuals whooccasionallyconsume (2 mealsper month)mussels fromGoose Cove thatcontain similarconcentrations ofmetals.

In order to make adefinitive healthcall, ATSDRrecommends thatadditional biotadata be collectedin an attempt togain moreinformation onthe potentialimpact tomussels, as wellas other shellfishand finfish. Anupdate to thisPHA willevaluate thenewly collecteddata to determinewhether ingestionof fish andshellfish isassociated withadverse healtheffects. At thecurrent time,ATSDRrecommends thatindividualscontinue toadhere to the fishand shellfishconsumptionadvisories thatalready exist inthe area. The banstates that noshellfish(including clams,mussels, andoysters) should becollected orconsumed fromGoose Pond,Goose Cove, andother nearbyareas.

Comment B3:The dismissal ofpotential ground-watercontamination isdisconcerting, asthat has thepotential to be thelargest health-hazard risk topeople who donot visit the site.Given theirregular strata inthe area and thereliance of thecommunity ondelocalizedground watersources, a morethorough study ofwell-water,especially at lowwater, iswarranted.

Response:ATSDR revieweddata fromdrinking waterwells samplednear the site from1986-1994. Dataindicates that nocontaminantswere present atconcentrationsthat exceedhuman healthcomparisonvalues. Therefore,no furtherevaluation of thedrinking waterexposurepathways wasconducted as partof this PHA.However,additionalsampling ofprivate drinkingwater wells hasbeen proposed byEPA as part of theRemedialInvestigation forthe site. ATSDRwill evaluatenewly collectedprivate well datato determinewhether exposuremay be associatedwith adversehuman healtheffects. Theconclusions ofthis PHA will bemodified ifnecessary.

Comments from acontractor forEPA:

Comment C1:The settling basinconsists of fine,powdery particlesleft from grindingthe rock for theconcentrativeextraction of ore.Much of the rocksurrounding theore body issiliceous, and thecontents of thesettling basincould be 50%silica. Silicosis intrespassers/recreators couldbe an endpoint.[The commenterprovided particlesize data from thesettling basin forreview byATSDR].

Response: Silicosis has beenobserved amongindividualsoccupationallyexposed torespirable (orfine, easilyinhaled)crystalline silicaover ten or moreyears (or chronicsilicosis) orexposed tomassivequantities ofrespirable silicaover one to threeyears (or acutesilicosis). Ingeneral, silicosisoccurs amongworkers whoengage inactivities thatgenerate verylarge quantities ofrespirable silica,such assandblasting, rockcrushing, grindingstone, highwayconstruction, orbuildingdemolition.Respirableparticle size isless than or equalto about 10micrometers, or10 one-thousandths of acentimeter.

The data providedby the commenteron particle sizewas reviewed byATSDR in anattempt to gaininformation onthe amount ofrespirable silicain the settlingbasin at theCallahan MineSite. It was notpossible todetermine theamount ofrespirableparticles presentin the settlingbasin because thedata provided didnot differentiateany particlessmaller than 74micrometers.Exposure to silicafrom the settlingbasin, that may beassociated withtrespassing orrecreationalactivities at theCallahan MineSite, is expectedto be short-termand infrequentand is not likelyto be associatedwith silicosis.However, in theinterest of healthprotectiveness,ATSDRrecommends thataccess to the sitebe restricted inorder to limit thepotential forexposure byindividuals whomay access thesite.

Comment from aprivate citizen:

Comment D1: Iwandered aroundthe mine site,including the flatcomposed of fine,powdery residue,for several yearsdoing naturalstudies. Imeasured andtook impressionsof animal tracksand collectedrocks and bones.

Response: This use of the site is not likely to result in a significantly increased risk of adverse health effects. In the public health assessment, we considered occasional use of the site (twice a week for thirty years) and concluded that there was not an increased risk of adverse health effects from such exposures.


APPENDIX D: ATSDR PLAIN LANGUAGE GLOSSARY OF ENVIRONMENTAL HEALTH TERMS

Absorption:
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.


Additive Effect:
A response to a chemical mixture, or combination of substances, that might be expected if the known effects of individual chemicals, seen at specific doses, were added together.


Adverse Health Effect:
A change in body function or the structures of cells that can lead to disease or health problems.


Antagonistic Effect:
A response to a mixture of chemicals or combination of substances that is less than might be expected if the known effects of individual chemicals, seen at specific doses, were added together.


ATSDR:
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.


Bioavailability:
See Relative Bioavailability.


Biota:
Used in public health, things that humans would eat - including animals, fish and plants.


Cancer:
A group of diseases which occur when cells in the body become abnormal and grow, or multiply, out of control


Cancer Slope Factor (CSF):
The slope of the dose-response curve for cancer. Multiplying the CSF by the dose gives a prediction of excess cancer risk for a contaminant.


Carcinogen:
Any substance shown to cause tumors or cancer in experimental studies.


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.


Community Assistance Panel (CAP):
A group of people from the community and health and environmental agencies who work together on issues and problems at hazardous waste sites.


Comparison Value (CV):
Concentrations 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. This act created ATSDR and gave it the responsibility to look into health issues related to hazardous waste sites.


Concentration:
How much or the amount of a substance present in a certain amount of soil, water, air, or food.


Contaminant:
See Environmental Contaminant.


Delayed Health Effect:
A disease or injury that happens as a result of exposures that may have occurred far in the past.


Dermal Contact:
A chemical getting onto your skin (see Route of Exposure).


Dose:
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".


Dose / Response:
The relationship between the amount of exposure (dose) and the change in body function or health that results.


Duration:
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 the Background Level, or what would be expected.


Environmental Media:
Usually refers to the air, water, and soil in which chemicals 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.


US Environmental Protection Agency (EPA):
The federal agency that develops and enforces environmental laws to protect the environment and the public's health.


Epidemiology:
The study of the different factors that determine how often, in how many people, and in which people will disease occur.


Exposure:
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:

  1. Source of Contamination,
  2. Environmental Media and Transport Mechanism,
  3. Point of Exposure,
  4. Route of Exposure, and
  5. 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.


Frequency:
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.


Ingestion:
Swallowing something, as in eating or drinking. It is a way a chemical can enter your body (see Route of Exposure).


Inhalation:
Breathing. It is a way a chemical can enter your body (see Route of Exposure).


LOAEL:
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.


Malignancy:
See Cancer.


MRL:
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.


NPL:
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.


NOAEL:
No Observed Adverse Effect Level. The highest dose of a chemical in a study, or group of studies, that did not cause harmful health effects in people or animals.


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.


PHA:
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.


Plume:
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). Some examples include: the area of a playground that has contaminated dirt, a contaminated spring used for drinking water, or the backyard area where someone might breathe contaminated air.


Population:
A group of people living in a certain area; or the number of people in a certain area.


PRP:
Potentially Responsible Party. A company, government or person that is responsible for causing the pollution at a hazardous waste site. PRP's are expected to help pay for the clean up of a site.


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.


Relative Bioavailability:
The amount of a compound that can be absorbed from a particular medium (such as soil) compared to the amount absorbed from a reference material (such as water). Expressed in percentage form.


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
- 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.


SARA:
The Superfund Amendments and Reauthorization Act in 1986 amended CERCLA (see CERCLA) and expanded the health-related responsibilities of ATSDR. CERCLA and SARA direct ATSDR to look into the health effects resulting from chemical exposures at hazardous waste sites.


Sample Size:
The number of people that are needed for a health study.


Sample:
A small number of people chosen from a larger population (see Population).


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.


Statistics:
A branch of the math process of collecting, looking at, and summarizing data or information.


Superfund Site:
See NPL.


Survey:
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.


Synergistic Effect:
A health effect from an exposure to more than one chemical, where one of the chemicals worsens the effect of another chemical. The combined effect of the chemicals acting together is greater than the effects of the chemicals acting by themselves.


Toxic:
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.


Toxicology:
The study of the harmful effects of chemicals on humans or animals.


Tumor:
Abnormal growth of tissue or cells that have formed a lump or mass.


Uncertainty Factor:
See Safety Factor.


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.

4. Environmental Protection Agency (EPA). Exposure factors handbook. Washington (DC): US Environmental Protection Agency, Office ofResearch and Development; 1999. Rpt. No.: EPA/600/C-99/001.
5. US Environmental Protection Agency (EPA), Office of Emergency and Remedial Response. Risk assessment guidance for Superfund, volume 1, human health evaluation manual. Washington (DC): US Environmental Protection Agency; 1989.
6. Agency for Toxic Substances and Disease Registry (ATSDR). Cancer policy framework. Atlanta (GA): US Department of Health and Human Services; 1993.



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