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Frequently Asked Questions (FAQs)
General FAQs
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What are PCBs?
PCBs or polychlorinated biphenyls are a class of chemicals consisting of 209 individual compounds. PCBs were widely used as a fire preventive and insulator in the manufacture of transformers and capacitors because of their ability to withstand exceptionally high temperatures. -
Why are PCBs of concern to humans?
PCBs are classified by the U.S. EPA as probable human carcinogens. In addition, EPA recognizes neurological and developmental effects as additional toxic effects of PCBs. The agency considers all PCB mixtures to be toxic. -
Why are there fish consumption advisories on the Hudson River?
PCBs bioaccumulate (see below) in fish. In 1976, the New York State Department of Environmental Conservation (NYSDEC) banned all fishing in the upper Hudson River, from the Troy Dam north through Fort Edward, because PCB levels in Hudson River fish were in excess of Food and Drug Administration limitations. In August 1995, a catch and release fishing program was instituted by NYSDEC in the upper Hudson where the total ban had previously been in place. Although it is now legal to catch and release fish in the Hudson north of the Troy Dam, one can still not safely consume the fish caught. In addition, there are health advisories posted for various Hudson River species in the river south of Troy. Women of childbearing age and children are at greatest risk. -
What does "Bioaccumulation" mean?
Bioaccumulation refers to the process by which contaminants such as PCBs accumulate or become magnified as they move up the food chain. PCBs concentrate in tissue and internal organs, and as big fish eat little fish, they accumulate all the PCBs that have been eaten by everyone below them in the food chain. Another term for this is Biological Magnification. -
What is the history of the PCBs in the Hudson River?
During a 30-year period ending in 1977, it is estimated that approximately 1.1 million pounds of PCBs were discharged into the Hudson River from two General Electric (GE) capacitor manufacturing plants located in Fort Edward and Hudson Falls, New York. Much of this PCB load adhered to fine sediments which accumulated behind the Fort Edward Dam. When the deteriorating dam was removed in 1973, the PCB-contaminated sediments were washed downstream. Studies conducted to evaluate the extent of the problem revealed that most of the contaminated sediments were in 40 hot spots which are situated in a 40-mile stretch of the river between Fort Edward and the Troy Dam. -
When will the dredging begin?
EPA anticipates that the dredging will begin May 2009.
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What is the status of EPA's offer to General Electric Company (GE) to implement the remedy for the Hudson River PCBs site?
EPA decided to retain certain aspects of the design work, including development of a community involvement program, development of performance standards and siting of sediment processing/transfer facilities. EPA's negotiations with GE for the implementation of the remedy are on-going. EPA entered into two Administrative Orders on Consent (AOC) with GE:- July 2002 AOC for an extensive sediment sampling program
- August
2003 AOC for the design of the remedy itself.
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What are engineering performance standards?
Engineering performance standards are technical requirements that help to ensure that the dredging of the Upper Hudson is done safely, stays on schedule and meets the human health and environmental protection objectives set forth in the February 2002 Record of Decision (ROD) for the site. Engineering performance standards are an important part of EPA's cleanup plan for the Hudson River. The ROD requires the development of performance standards for dredging-related resuspension of sediments from the river bottom, residual levels of PCBs after dredging occurs, and the productivity of the dredging work. -
Why are quality of life performance standards needed for the dredging project?
In response to public concerns, the quality of life performance standards for air quality, noise, odor, lighting, and navigation were developed by EPA to minimize the impacts of the Hudson River cleanup on local communities. These standards honor a commitment to a process that provides accountability and transparency. -
What is a Natural Resource Damages Claim?
A Natural Resource Damage Claim seeks financial compensation for damages done by a polluter to a natural resource (such as a river). It is completely separate from EPA's Reassessment Study and any remedial action that may be warranted. Certain agencies are given the title of Natural Resource Trustee under the Superfund law and are empowered to pursue Natural Resource Damage Claims. -
Who are the Trustees of the Hudson River?
The Trustees are the following agencies or entities: the State of New York, the U.S. Department of Commerce, represented by the National Oceanic and Atmospheric Administration (NOAA), and the U.S. Department of the Interior, represented by the U.S. Fish and Wildlife Service. The EPA is not a Trustee.
FAQs About PCB Health Risk
- What
do other Agencies say about cancer and PCBs?
EPA's concern regarding the carcinogenicity of PCBs (the ability of PCBs to cause cancer) is shared by other agencies. The International Agency for Research on Cancer (IARC)
has declared PCBs to be a probable carcinogen in humans based on sufficient
evidence in animals and limited evidence in humans. IARC was established
in 1965 by the World Health Organization to coordinate and conduct research
on the causes of human cancer, and to develop scientific strategies
for cancer control. In addition, the National
Toxicology Program
,
a part of the National Institutes of Environmental Health Science (NIEHS),
has concluded that PCBs are reasonably anticipated to be carcinogenic
in humans based on sufficient evidence in animals. The National
Institute for Occupational Safety and Health (NIOSH)
has
determined that PCBs are a potential occupational carcinogen.
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How is the toxicity of PCBs determined?
To evaluate the potential toxicity of chemicals and the levels associated with the toxicity, EPA uses data from human epidemiological studies, laboratory animal toxicity studies and supporting information that may include structure activity analysis or tests on cells.
Epidemiology is the study of the causes of disease. One type of human epidemiological study looks at people who have been exposed to the chemical over a long period of time. These studies evaluate the occurrence of disease in the exposed population with the occurrence of disease in a non-exposed population. PCB epidemiology includes studies of workers exposed in factories that manufactured capacitors and people exposed by eating contaminated fish.
The advantage of human epidemiological studies in determining human health risk assessment is obvious since we are concerned with risk to humans. The disadvantages include the difficulties in determining exposures that may have occurred over 30 years ago (based on known cancer lag times), finding individuals who may have moved over this long time period, the potential for populations to be exposed to other chemicals in addition to PCBs, and the fact that exposures may be limited to healthy workers while children, pregnant women and others in the general population may be of special concern to EPA. Epidemiological evidence provides important information that can be refined in laboratory experiments where animal exposures can be controlled.
Animal toxicity studies are primarily conducted on mice, rats, and to a lesser extent in monkeys. These species share a similar evolutionary history to humans. The studies are conducted with appropriate animal safeguards including prior approval by institutional review boards on animal experimentation. Animal toxicity studies are designed to expose groups of laboratory-bred animals to:- different levels of PCBs,
- for varying portions of the animal's lifetime, and
- through different routes of exposure (breathing, eating, etc.).These
experiments provide information necessary to help determine short
or longer term effects on the body, specific organ systems and biochemical
processes (i.e., enzyme levels). The advantage of these studies
is that the conditions of dose and exposure can be controlled and
the specific effects of the PCBs evaluated. The disadvantage is
that animals are not the primary species of concern for human toxicity.
However, the value of animal studies has been well established.
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How does EPA evaluate PCB toxicity information?
EPA scientists evaluate data from published human epidemiological and animal toxicity studies. The main questions are: - Do PCBs have the potential to cause cancer in humans?
- And if so, at what level?
- What other effects can PCBs cause in the body?
Through the Integrated Risk Information System (IRIS) process, EPA scientists evaluate the available scientific literature and develop a chemical file summarizing the available information and EPA's conclusions about the health effects of PCBs. The IRIS PCB files describe the non-cancer and potential cancer effects. These documents are reviewed by EPA scientists and scientists outside the Agency (external peer-reviewers).
As new information becomes available, EPA may re-evaluate the toxicity data to determine if a reassessment of health effects may be necessary. For example, in 1996, based on new scientific information, the Agency re-evaluated the potency of PCBs and updated the IRIS cancer assessment file. Currently, EPA is reevaluating the non-cancer health effects of PCBs, with a report anticipated in the year 2000.
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Do PCBs cause cancer?
EPA evaluates the ability of a chemical to cause cancer based on the weight of evidence of human epidemiological and animal toxicity studies. EPA also develops risk factors that indicate the relative potency of the chemical (the ability of a given quantity or dose to cause cancer).
Weight of Evidence: PCBs are classified as probable human carcinogens or likely to be carcinogenic in humans. As described in the IRIS file, the basis for this determination is a 1996 study in rats (sponsored by General Electric; reviewed by EPA and external peer reviewers) that found increased numbers of liver tumors in female rats exposed to Aroclors 1260, 1254, 1242 and 1016 and in male rats exposed to Aroclor 1260. These mixtures contain overlapping groups of congeners that, together span the range of congeners most often found in environmental mixtures. The findings of the 1996 GE study strengthened earlier studies which also demonstrated carcinogenicity in rats. Several epidemiological studies on human populations are being updated. EPA's evaluation of human epidemiological studies as summarized in IRIS identified limitations including the small number of individuals studied, short follow-up periods and confounding from exposures to other potential carcinogens. As a result, current human epidemiological evidence is inadequate to classify PCBs as known human carcinogens, but is suggestive that PCBs may cause cancer in humans.
Risk Factors: To quantify the potential for PCBs to cause cancer, EPA developed three cancer slope factors based on the 1996 GE rat study. The different cancer slope factors deal with different routes of exposure. A cancer slope factor is an upperbound estimate of excess lifetime cancer risks per unit dose or exposure to a carcinogen. It is presented in risk per (mg/kg)/day. The highest slope factor is for ingestion (i.e., food chain) exposure. The Cancer Slope Factor Chart provides a list of the cancer slope factors for ingestion, inhalation and dermal exposure to PCBs in units of milligrams of material ingested/bodyweight in kilograms per day. - How are
non-cancer health effects evaluated?
EPA evaluates all animal studies of non-cancer health effects to identify the study (critical study) that is most representative of human PCB exposure and that meets rigid scientific criteria. The analysis identified the level where there were no observed adverse effects. Based on the literature, the Agency identified the critical studies for Aroclor 1254 and Aroclor 1016 (presented in tabular form) and described below.
Aroclor 1254: The critical study identified was a study of rhesus monkeys conducted by Dr. Arnold and others in 1994. The monkeys were exposed to varying doses of PCBs ingested in gelatin capsules for a period of five years. The critical effects identified were suppression of the immune system, inflammation of the Meibomian gland (a small gland in the inner portion of the eye), and distorted growth of fingernails and toenails. EPA developed a Reference Dose, the level below which adverse effects on the humans are not expected. EPA took the Lowest Observed Adverse Effect Level (LOAEL) found in the monkey study and divided it by a factor of 300 to protect sensitive humans.
The factor of 300 (reduction from animal to human exposure) was based on an evaluation of toxicity studies and the application of established factors for extrapolating from animals to humans. The Rhesus monkey has similar (to human) toxic responses and metabolism of PCBs in addition to sharing a general physiological similarity. Rhesus monkey studies predicted other changes noted in human studies such as chloracne, hepatic (liver) changes and effects on reproductive function. Where a NOAEL cannot be identified or where a less than lifetime animal study was conducted, individual factors of 10 are applied in all studies in extrapolating from animals to humans to protect sensitive humans (including children). These factors of 10 may be reduced to 3 by EPA scientists, based on the available information. For example, with Arochlor 1254, a full factor of 10 was used to protect sensitive humans. The other factors were reduced to approximately 3 based on the availability of studies in Rhesus monkeys. The factors are then multiplied together and rounded to the nearest integer, resulting in the factor of 300 for Aroclor 1254.
Aroclor 1016: The critical studies identified were monkey reproductive studies conducted by Drs. Barsotti and VanMiller in 1994, Dr. Levin and others in 1988 and Dr. Schantz and others in 1989 and 1991. These are a series of reports that evaluated toxicity around birth and long-term neurobehavioral effects of Aroclor 1016 in the same groups of infant monkeys. In the studies, groups of eight female monkeys were exposed through diet seven months before delivery and four months immediately following delivery. The critical effect identified at the No Observed Adverse Effect Level (NOAEL) was reduced birth weights. In developing the Reference Dose, the NOAEL was divided by a factor of 100 to protect sensitive humans, including children..
A procedure similar to that described (above) for Aroclor 1254 was applied to extrapolate from Rhesus monkeys to humans. The uncertainty factor for Aroclor 1016 was 100. Based on the monkey reproductive studies, a full factor of 10 was not deemed appropriate since infants exposed through the placenta represent a sensitive subpopulation. An additional factor of 3 was applied since information on male reproductive effects and second generation studies were not available. The other factors for less than chronic exposure, and from animals to humans, was the same for both Aroclors 1254 and 1016. These factors were multiplied together and rounded, yielding a factor of 100.
- What is risk assessment?
Risk assessment is a process used by EPA to determine the potential health effects in humans (cancer and non-cancer) associated with exposure to chemicals. Risk assessment is used throughout EPA to evaluate chemical toxicity and potential health effects in humans.
Under Superfund law (Comprehensive Environmental Response, Compensation and Liability Act -- CERCLA), EPA is required to conduct a baseline risk assessment that evaluates current and future risks at all Superfund sites. Risk assessment was defined in 1983 by the U.S. National Academy of Sciences as involving one or more of the following four steps:- Hazard identification - Do PCBs have the potential to cause cancer? What other health effects (such as changes in the immune system, reduced birth weight, etc.) are caused by PCBs?
- Dose response - What amount of PCBs in the human body causes these effects?
- Exposure assessment - How people are exposed to PCBs (i.e., eating, drinking, breathing, skin contact) and at what levels.
- Risk characterization - The answers to the above three questions
are used to calculate what risk an individual having significant
exposure runs of developing cancer or experiencing a non-cancer
effect. The uncertainties connected with answering the
three questions are also described. The risk characterization is
then used by risk managers in their decision making process.
- How is exposure to
PCBs evaluated?
To evaluate exposure, the Agency looks at the concentration of PCBs in fish, water, soil, sediment and air; the frequency with which an individual may come into contact with the media; the length of time the individual may be exposed, and the bodyweight of the individual. For carcinogens, the exposure is averaged over a lifetime. For non-carcinogenic effects, exposure is averaged over the portion of the lifetime during which the exposure occurs. Depending on the data available, separate analyses can be developed for children, adults and lifetime exposure.
The data used in the assessment may be based on actual concentrations in the fish, soil, etc. It may also be based on modeling that projects future concentrations. Information on exposure activities may be developed using national or local surveys of activities (i.e., fish consumption). The result of the exposure evaluation is a calculated level of dose for each route of exposure.
- How are risks calculated?
Cancer risk calculates the increased probability of an individual developing cancer based on a number of assumptions concerning PCB exposure. The risks are calculated by multiplying the dose (from exposure) by the toxicity (cancer slope factor -- see above). The individual risks for each pathway are added together to reflect the total cancer risk. The risk characterization presents the calculated risks along with discussion of uncertainties.
- How are hazards calculated?
Non-cancer hazards are calculated by comparing the dose (from exposure) with the Reference Dose. Exceeding the Reference Dose results in an increased potential of adverse health effects. The individual hazards from each pathway are added together to reflect the total hazard. The uncertainties associated with the exposure assumptions and Reference Doses are detailed in the risk characterization.
- How is
risk assessment used by risk managers?
The results from the risk assessment (cancer risk and non-cancer hazards) are used by the risk manager during the Feasibility Study, Proposed Plan and Record of Decision to determine the need for future action at the site.
For information about this page, contact: skopeck.kristen@epa.gov