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1. ATSDR > Public Health Assessments & Consultations

PUBLIC HEALTH ASSESSMENT

EASTERN SURPLUS COMPANY SITE
MEDDYBEMPS, WASHINGTON COUNTY, MAINE

APPENDIX C: OPERATIONAL AND REGULATORY EVENTS AT THE EASTERN SURPLUS SITE

Source: 1, 2

APPENDIX D: ATSDR PUBLIC HEALTH ASSESSMENT METHODOLOGY

Quality Assurance

In preparing this report, the Agency for Toxic Substances and Disease Registry (ATSDR) reviewed and evaluated information provided in the referenced documents. Documents prepared under the Superfund program must meet specific standards for adequate quality assurance and control measures for chain-of-custody procedures, laboratory procedures, and data reporting.

The groundwater, private well, surface soil, surface water, sediment, air, fish, and shellfish data presented in the Remedial Investigation (1) were validated to assure that samples were analyzed in accordance with quality control requirements stipulated by EPA for Superfund sites. No significant 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 exposure pathways. An exposure pathway is the way chemicals may enter a person's body to cause a health effect. It includes all the steps between the release of a chemical and the population exposed: (1) a chemical release source, (2) chemical movement, (3) a place where people can come into contact with the chemical, (4) a route of human exposure, and (5) a population that could be exposed. In this assessment, ATSDR evaluates contaminants found in different media that 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 evaluate environmental data that is relevant to the exposure pathways. CVs are concentrations of contaminants that are considered to be safe levels of exposure. CVs used in this document include ATSDR's environmental media evaluation guide (EMEG) and cancer risk evaluation guide (CREG), as well as the U.S. Environmental Protection Agency's (EPA) risk-based concentrations (RBCs). CVs are derived from available health guidelines, such as ATSDR's minimal 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 are much lower than exposure concentrations observed to cause adverse health effects; thus, insuring the CVs are protective of public health in essentially all exposure situations. That is, if the concentrations in the exposure medium are less than the CV, the exposures are not of health concern and no further analysis of the pathway is required. However, while concentrations below the CV are not expected to lead to any observable health effect, it should not be inferred that a concentration greater than the CV will necessarily lead to adverse effects. Depending on site-specific environmental exposure factors (for example, duration of exposure) and activities of people that result in exposure (time spent in area of contamination), exposure to levels above the CV may or may not lead to a health effect. Therefore, ATSDR's CVs cannot be used to predict the 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, of soil which, assuming default values for (adult) body weight and intake rates, would correspond to exposure doses estimated to produce no more than one excess cancer in a million persons exposed. CREGs are calculated from EPA's cancer slope factors and therefore reflect estimates of "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 of CVs because it assumes that no threshold exists for the effects of chemical carcinogens. The resulting CREG can therefore often be below typical background levels and common detection limits. CREGs do not define levels of actual hazard (e.g., a 1-in-a-million "risk" level) and cannot be used to predict actual cancer incidence under specified conditions of exposure. As stated in EPA's 1986 Cancer Risk Assessment Guidelines, "the true risk is unknown and may be as low as zero."

Environmental Media Evaluation Guides (EMEGs) are concentrations of a contaminant in air, water, or soil that are calculated from ATSDR's MRLs for acute, intermediate, or chronic exposure by factoring in default body weights and ingestion rates for adults and children (and, in the case of soil, pica children). The MRLs on which the EMEGs are based are ATSDR's estimates of daily human exposure doses of a contaminant (expressed in milligrams or contaminant per kilogram of body weight per day [mg/kg/day]) that ATSDR considers unlikely to be associated with any appreciable risk of harmful noncancer effects over a specified duration of exposure. MRLs are calculated using data from human and animal studies and, like the EMEGs derived from them, are reported for acute (< 14 days), intermediate (15-364 days), and chronic (> 365 days) exposures. MRLs are published in ATSDR Toxicological Profiles for specific 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 exposure is unlikely to result in adverse noncarcinogenic effects.

Lifetime Health Advisories for Drinking Water (LTHA) are derived by EPA based on information about the toxicity of a contaminant. LTHAs are considered the concentration of a contaminant in drinking water that is not expected to cause adverse noncancer health effects for a lifetime of exposure in drinking water.

Maximum Contaminant Levels (MCL) are drinking water standards established by EPA. They are the maximum permissible level of a contaminant in water that is delivered to the free-flowing outlet. MCLs are considered protective of public health over a lifetime (70 years) for people consuming 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 with standard exposure scenarios, such as ingestion of 2 liters of water per day, over a 70-year life span. RBCs are contaminant concentrations that are not expected to cause adverse health effects over long-term exposures.

Soil Screening Levels (SSL) were derived by EPA for nation-wide application to sites used for residential areas. SSLs are estimates of contaminant concentrations that would be expected to be without noncancer health effects over a specified duration of exposure or to cause no more than one 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 the health assessor identifies for further evaluation of potential health effects. Identifying these contaminants is a process that requires the assessor to examine contaminant concentrations at the site, the quality of environmental sampling data, and the potential for human exposure. A thorough 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 concentrations are compared directly to CVs. ATSDR considers site-specific exposure factors to ensure selection of appropriate CVs. If the maximum concentration reported for a contaminant was less than 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 maximum concentration 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 for additional data review.

CVs have not been developed for some contaminants, and, based on new scientific information other CVs may be determined to be inappropriate for the specific type of exposure. In those cases, the contaminants are included as contaminants of concern if current scientific information indicates 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 contaminants selected. Factors used in the selection process included the number of samples with detections above the minimum detection limit, the number of samples with detections above an acute or chronic health comparison value, and the potential for exposure at the monitoring location.

APPENDIX E: GLOSSARY

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.

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.

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

Carcinogen:

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

CERCLA:

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.

Concern:

A belief or worry that chemicals in the environment might cause harm to people.

Concentration:

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

Contaminant:

See Environmental Contaminant.

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".

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 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.

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.

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:

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.

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). 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.

Population:

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.

SARA:

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.

Statistics:

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

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.

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.

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.

APPENDIX F: ARSENIC IN PRIVATE WELLS NEAR THE EASTERN SURPLUS SITE

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, that arsenic in these private wells is associated with adverse health effects, ATSDR derived exposure doses and evaluated the weight of evidence for arsenic toxicity. Deriving exposure doses requires evaluation of contaminant concentrations and length of exposures. Together, these factors help influence the individual's physiological response to chemical contaminant exposure and potential outcomes. In the absence of complete exposure-specific information, ATSDR applied several conservative exposure assumptions to define site-specific exposures as accurately as possible for the private wells users.

ATSDR derived exposure doses using the following assumptions about a person's use of private well 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 minimal risk levels (MRLs) and EPA's reference doses (RfDs). The chronic MRLs and RfDs are estimates of daily human exposure to a substance that are unlikely to result in adverse noncancer effects over a specified duration. To be very protective of human health, MRLs and RfDs have built in "uncertainty" or "safety" factors that make them much lower than levels at which health effects 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 doses to the cancer effect level (CEL). The CEL is the dose at which tumors, or cancer effects, are seen in laboratory or epidemiology studies.

For noncancer effects, ATSDR found that exposures to the maximum detected concentration of arsenic (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 are just slightly above the MRL/RfD for a child. Even though the estimated doses for a child slightly exceed the MRL/RfD for arsenic, we do not expect that a child drinking water at these taps will experience health effects. First, ATSDR assumed that a child was exposed for an extended period of time to the highest level of arsenic measured in the private wells. This provided a very conservative estimate of potential exposure because a child probably did not drink from the same well or drink the highest levels of arsenic for this estimated length of time. Second, as noted, the MRL/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 adverse health 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 a wide variety of adverse health effects in humans, but at doses higher than those resulting from drinking the maximum arsenic concentrations detected in the private wells. Symptoms of chronic oral exposure appear to be skin problems (e.g., hyperkeratosis, hyperpigmentation), neurological effects, 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 of 0.014 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 the Eastern 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. EPA has 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 epidemiologic studies. One of the most cited studies is a Taiwanese study in which the lowest exposure levels associated with the onset of cancer (skin) were observed in people drinking water containing 170 to 800 ppb arsenic for a 45-year exposure period (16). Although the study demonstrated an association between arsenic in drinking water and skin cancer, the study failed to account for a number of complicating factors, including exposure to other nonwater sources of arsenic, genetic susceptibility to arsenic, and poor nutritional status of the exposed population. Furthermore, arsenic exposure may have been underestimated in the study, possibly leading to an overestimation of the actual risk. These weakness and uncertainties may limit the study's usefulness in evaluating cancer risk for residents drinking water containing arsenic near the Eastern Surplus site.

Furthermore, various studies indicate that at low level exposures, arsenic compounds are detoxified (or metabolized)--that is, changed into less harmful forms--and then excreted in the urine. 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 0.5 mg/kg/day, which is much higher than the dose level estimated here (16). When our body's capacity to detoxify is exceeded, blood levels of arsenic increase and adverse health effects may occur. This appears to be true for cancer and noncancer effects. At lower doses, scientists continue to study the relevance between metabolism and toxicity.

At EPA's request, a special subcommittee of the National Research Council (NRC) reviewed the arsenic toxicity data base and evaluated the scientific basis of EPA's risk assessment for arsenic in 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, including cancer, but those levels are much higher than those measured in the private wells. While scientists are still uncertain about the health effects, if any, of long-term, low level exposure to arsenic in drinking water, enough evidence exists to suggest that arsenic is tolerated by humans at low doses. Given this information, ATSDR does not believe that arsenic at the levels measured in the private wells near the Eastern Surplus site are high enough to cause adverse health effects or cancer.

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Agency for Toxic Substances and Disease Registry, 1825 Century Blvd, Atlanta, GA 30345
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