PUBLIC HEALTH ASSESSMENT
AIR AND GROUNDWATER PATHWAYS ANALYSES
AGANA POWER PLANT
September 22, 2004
Comparison of Public Health Assessments and Risk Assessments [PDF, 476KB]
- How do PCBs enter and leave the body?
- What are the health effects from PCB exposure?
For most people who do not work with polychlorinated biphenyls (PCBs), consumption of PCB- contaminated fish, meats, eggs, and dairy products is the most common and significant sources of human exposure to PCBs (ATSDR 2000). PCBs that are swallowed are passed from the gastrointestinal tract into the bloodstream. Once PCBs are in the body, some change into other related chemicals called metabolites and some leave the body in feces in a few days. The remaining PCBs and metabolites stay in the body and can be stored for years mainly in the body fatty tissue. PCBs also accumulate in human milk fat (ATSDR 2000).
Everyone has some amount of PCBs in their body through environmental exposures worldwide. Since PCBs are so widespread, don't break down easily in the environment, and can accumulate in people, they have been heavily studied.
From the thousands of PCB studies conducted since the 1960s, the effect of low-level exposures to PCBs on human health remain inconclusive. Most of the human studies have many limitations that make it difficult to establish a clear association between PCB exposure and health effects.
- Skin Effects: Effects seen from over-exposure in occupational settings include chloracne, hyperpigmentation of the nails & skin, and skin irritation. These symptoms generally disappear when PCB exposure stops (ATSDR 2000).
- Developmental Effects: There are no reports of structural birth defects in humans caused by PCB exposure. Several recent studies suggested that children born to mothers who ate PCB-contaminated fish during their pregnancies may have had an increased risk of developing subtle (i.e., not easily observable) nervous system delays (e.g., abnormal reflexes, motor immaturity, deficits in memory, learning, and IQ), which in some cases persisted into adolescence, but returned to normal in most cases within the first 2-4 years. These effects were only seen when large populations were studied and tended to be within the normal range of variation. The clinical relevance of these effects, particularly for individual children, is unknown. Other studies, however, did not find these associations and any changes that were observed disappeared upon later study (ATSDR 2000).
- Cancers: Some human studies provide suggestive evidence that PCBs are carcinogenic based on indications of PCB- related cancer in areas such as the liver, biliary tract, intestines, and skin (ATSDR 2000). Studies have shown that animals exposed to high levels of PCBs over their lifetimes developed liver and kidney tumors (ATSDR 2000). On the basis of the observed cancer in animals, the Department of Health and Human Services concluded that PCBs might reasonably be anticipated to be carcinogens (ATSDR 2000). Both the U.S. Environmental Protection Agency and the International Agency for Research on Cancer have determined that PCBs are probably carcinogenic to humans (ATSDR 2000). This designation means that a clear cause-and-effect relationship has not been established in humans but there is sufficient evidence to take precautions about exposure to this chemical. ATSDR continues to support recommendations by health and regulatory agencies to reduce exposure to PCBs.
Yes, there are tests that measure PCB levels in the blood, fat tissue, and breast milk. Blood tests are the safest and easiest method for detecting PCB exposure. These tests only indicate whether someone was exposed to a greater extent than the general population. They cannot determine the type and amount of PCB, how long someone was exposed, or whether they will become ill. Therefore, they do not assist physicians in providing better treatment. Measuring the level of a chemical is different from establishing its effects. Everybody will have some detectable amount of PCBs in their blood, fat, and breast milk. The medical significance of detectable blood PCB levels is unclear.
Regardless of whether or not a person has a medical test, the recommendations are the same. Determine if hazardous environmental exposures are likely; if so, find out from what source and reduce exposure to that source(s). For example, it can help to determine whether or not fish advisories should be in place and what types of education or risk management decisions are needed to communicate information on: fish species that can safely be consumed, changing diets, and the preparation of foods (e.g, not eating the entire fish, trimming fat).At this time there is no treatment for PCB exposure. People with high levels should have a careful exposure history taken and increase efforts to identify and eliminate any current sources of PCB exposure.
- Can I have children?
Regardless of PCB exposure, a health care provider should be consulted before making this decision.
There have been no studies that report structural birth defects as a result of PCB exposure (ATSDR 2000). Studies of highly exposed workers suggest a slight effect on birth weight and gestational age (Kimbrough 1995). PCBs are believed to play a role in neurological development, but the changes are subtle (ATSDR 2000). Human studies provide some evidence of effects on the immune system in infants exposed to PCBs in utero and/or via breast milk that might make them more susceptible to infections. However, this evidence is limited because of mixed chemical exposures and insufficient information on exposure-response relationships (ATSDR 2000).
- Can I breast-feed?
PCBs detected in breast milk (or blood) are not necessarily an indication that breast-feeding should be stopped (ATSDR 1990). Benefits of breast-feeding can include fewer ear infections, higher immunity from diseases, and improved nutrition. In most cases, the benefits of breast-feeding probably outweigh any potential risks (ATSDR 2000).
- Should my physician monitor my children for neurodevelopmental delays?
Physicians should monitor children for the usual developmental parameters and do not need to change their practices.
- Should my physician monitor me for cancer?
Physicians should monitor people as usual and don't need to change their practices.
Agency for Toxic Substances and Disease Registry. Toxicological profile for polychlorinated biphenyls (PCBs) (update). Atlanta: US Department of Health and Human Services; 2000 Apr.
Agency for Toxic Substances and Disease Registry. Polychlorinated biphenyls (PCBs) toxicity, case studies in environmental medicine. Atlanta: US Department of Health and Human Services; 1990.
Kimbrough, RD. Polychlorinated biphenyls (PCBs) and human health: an update, critical reviews in toxicology. 25(2):133-163, 1995.
Press Release and Questions and Answers about Dioxins [PDF, 1,191KB]
During the public comment period and during the site visit in May 2004, the Agency for Toxic Substances and Disease Registry (ATSDR) received some comments from residents and additional comments from the Navy and representatives from various Guam Government agencies. These comments were either editorial in nature (e.g., syntax or spelling corrections to text) or requests for additional perspective pertaining to potential exposure pathways or health outcomes related to site-related chemicals from Agana Power Plant.
The comments along with corresponding responses ATSDR received are provided below.
Comment: Navy Comment. The bottom of page 1 concludes, "Exposures to chemicals including PCBs should be reduced, to the extent practical, by remedial action." The Navy has completed the majority of remedial activities associated with chemical spills related to the power plant. Text should state that "Exposure to chemicals have been reduced, to the extent practical, through remediation."
Response: ATSDR has revised the text in the document accordingly
Comment: Navy Comment. The bottom of page 8 states that the groundwater flows northwest toward the Philippine Sea, away from the Agana Swamp. Page 18 states, "During the groundwater investigation, the Navy calculated the groundwater flow direction to be northwest toward Agana Bay and the Philippine Sea. Page 19 concludes with the statement "Groundwater measurements from existing monitoring wells indicate that groundwater flow is toward the mouth of the Agana River, contrary to the idea that the groundwater flowed towards Agana Swamp. The more recent information on Page 19 should be included in the discussion on pages 8 and 18.
Response: ATSDR has revised the text in the document accordingly
Comment: Navy Comment. The second paragraph on page 21 compares the concentrations detected to maximum contaminant levels (MCLs). The footnote to Table 1 briefly describes what an MCL represents. We feel it may be appropriate to provide a proper definition of what an MCL represents within the text or add MCL to Appendix E: "ATSDR Glossary of Terms."
Response: ATSDR has added a definition of maximum contaminant level (MCL) to the glossary in Appendix E and referenced it in the appropriate place in the text.
Comment: Concern about additional biota sampling. "I would like to see further testing of aquatic animals. The species most commonly consumed on Guam include tilapia, eels, shrimp, and the snails. More testing of tilapia should be considered, as well as testing of shrimp and eels.
Response: Past sampling efforts of fish and other biota showed that PCBs and dioxins are not at levels known to cause harm. However, ATSDR supports continued monitoring efforts by the Navy and other responsible parties in order to ensure that commonly consumed fish such as tilapia and other potential food sources from the Agana Swamp and River are safe to eat. The Navy and regulatory agencies are discussing the possibility of additional sampling of fish and aquatic organisms to determine if there are downward trends in PCB levels and to further evaluate fish consumption advisories in the Agana River and Swamp.
Comment: Concern about better explanation of health effects of PCBs and how cumulative ingestion of PCB-contaminated fish and other food items affects health.
Response: There is clear evidence that PCBs have significant toxic effects in animals, including effects on the immune system, the reproductive system, the nervous system and the endocrine system. Some epidemiological (i.e., human) studies have supported the animal studies in observing potential health effects. For example, a number of epidemiological studies of workers exposed to PCBs have found increases in rare liver cancers and malignant melanoma. The presence of cancer in the same target organ (liver) following exposures to PCBs both in animals and in humans and the finding of liver cancers and malignant melanomas across multiple human studies adds weight to the conclusion that PCBs are probable human carcinogens.
However, other epidemiological studies have resulted in findings that are not as easy to interpret and some of the studies in humans have not demonstrated any association between exposures to PCBs and disease. This may be due to limitations in study design and methodology that can affect the ability to discern important health effects (or define them as statistically significant) even when they are present. Often, the number of individuals in a study is too small for an effect to be detected or there are difficulties in determining actual exposure levels. There may also be multiple confounding factors (i.e., factors that tend to co-occur with PCB exposure, including smoking, alcohol consumption, and exposure to other chemicals in the environment). Epidemiological studies may not be able to detect small increases in health outcomes such as cancer over background unless the cancer rate following contaminant exposure is very high or the exposure produces a very unusual type of cancer. Limited studies that produce inconclusive findings for cancer in humans do not mean that PCBs are safe. Appendix I contains additional information about the health effects of both dioxins and PCBs to further place the human health risks in perspective.
Given the most currently available information in the scientific literature about how PCB exposure over time may impact health, it is not possible to tell an individual what specific harm (e.g., development of cancer, other health effects, or more subtle changes at a cellular level) may occur from the relatively low doses that we believe people living in the vicinity of Agana Power Plant have been exposed over their lifetime. A review of the most current toxicological data strongly suggests that residents in the Mongmong-Toto-Maite District would not have any adverse health effects from the levels of PCBs that were detected in soils, sediment, surface water, and groundwater. However, ATSDR acknowledges that there is some level of uncertainty about historical PCB concentrations in the study area and whether there is a threshold level at which exposures cause no harm. Concern about PCBs is related to concern about Dioxin and Dioxin like compounds especially TCDD. As further discussed in appendix I, TCDD levels in Americans have declined in recent years as a result of environmental controls but is still widely detected in the environment and can be found in very small amounts in the general population. The Report on Carcinogens is a cancer health hazard identification document that discusses substances that may pose a carcinogenic hazard to human health. The report does not present quantitative assessments of carcinogenic risk, an assessment that defines the conditions under which the hazard may be unacceptable. The listing of substances in the report, therefore, does not establish that such substances present carcinogenic risks to individuals in their daily lives.
Understandably, this uncertainty can be frustrating. However, as advances in science and research methodology continue to improve we hope that these uncertainties can be resolved. In the mean time ATSDR recommends that people reduce, to the greatest extent possible, exposure to PCBs and other related compounds (e.g., dioxins, certain pesticides). Since we do know that most non-point exposure comes from ingesting PCB-contaminated foods, this can be accomplished quite effectively by; 1) trimming fat from fish and meats; 2) not consuming organ meats and skin that readily accumulate PCBs; and 3) obtaining local foods (i.e., fish, meats, and produce) from a variety of locations to reduce the possibility of always harvesting from one area that could potentially be contaminated.
Comment: Concern that lack of fish had adverse impact on health because food resources are no longer available for subsistence or semi-subsistence or heavy recreational fishing to supplement diet.
Response: ATSDR acknowledges the importance of harvesting fish and other edible foods to some of the native islanders as a means of supplementing dietary requirements. We strongly encourage all residents of Guam to contact local Guam Government officials (e.g., Division of Aquatic and Wildlife Resources [DAWR], U.S. Fish and Wildlife Services (USFS), and Guam Coastal Management) to inquire about the most suitable locations for harvesting fish and other local edible foods near your home.
Comment: Concern that Agana Spring is major source area for PCBs and Dioxins in addition to transformer pad near the springs.
Response: On the basis of all the available sampling data, the transformer pad near the Agana Springs appears to be an isolated hot spot and was not representative of other portions of Agana Springs. The Navy's sampling investigations did include collecting soil and sediment samples at other Agana Springs locations near the transformer pad and PCBs at these locations were detected at much lower concentrations. For example, the average PCB (Aroclor 1260) concentration excluding the sample collected at the old transformer pad was 1.1 ppm. The available sampling data for Agana Springs did not include dioxin analyses and it is not possible to make any statements regarding dioxins. ATSDR does recommend that the PCB hot spot at the old transformer pad be cleaned up to residential standards.
Comment: Concern that historical Incinerator near the mouth of the river was not considered as source of Dioxins in the swamp.
Response: Although ATSDR did not specifically investigate the former incinerator; dioxin levels in sediments, fish and other edible foods (e.g. snails) in the swamp were very low or below detection level. Since dioxins are very persistent and have very long half-lives in sediments, there is no reason to believe that historical releases associated with this incinerator contributed to dioxin in sediments and biota in the swamp at levels that would have been harmful.
Comment: Concern about worker exposure to PCBs during installation of sewage pipeline.
During the meeting with Guam Territorial agencies, Guam Coastal Management voiced concern that PCBs may have been present during sewage pipe digging and installation operations.
Response: ATSDR has limited information to evaluate the potential for PCB exposure resulting from excavating soil and installing sewage pipelines. ATSDR noted that PCBs were detected in surface and shallow subsurface soils. However, as previously stated, with few exceptions PCB levels have not been detected in off-site soils at levels that are known to cause health effects in people. It is very important to understand that even if workers did come across an isolated hot spot where PCB levels were very high, the exposure duration would be short and cumulative dose would still be very low compared to people who worked for years in industries that were associated with PCB use (e.g., transformer assembly and maintenance workers).
Employees who are concerned about PCBs or other chemical exposures at this site or any other site should contact their health care provider. For former employees living on Guam, please contact:
Department of Labor
Workers' Compensation Commission
Government of Guam
Post Office Box 9970
Tamuning, Guam 96931-9970
Telephone: (671) 647-4205; fax: (671) 649-4922
Comment: Concern about radon combined with PAHs, particulates and other compounds have a combined impact on lung diseases.
Response: Radon is a gas that is derived from the radioactive decay of radium, a natural element found in rock and soil. Radon gas can enter homes through building foundations and accumulate in indoor air. Radon is measured in picocuries per liter (pCi/l) and EPA's recommended action level for radon is 4 pCi/L. Guam EPA has a program to evaluate radon in homes, schools, and buildings in selected locations across the island. Radon levels can vary considerably depending on construction, geologic formations, and ventilation systems within each home or building. Therefore, it is important for home or property owners to have their property evaluated for radon.
There is no evidence that PAHs detected in soil and water, which is more likely to be ingested, rather than inhaled, combined with radon exposure increases an individual's risk of developing lung cancer or other lung diseases. The evidence does show that PAHs entering the body from inhalation exposure increase the risk of developing lung cancer or other lung disease. One of the most important synergistic relationships (i.e., two independent factors combining to make a condition worse or increase the risk of developing a disease) associated with lung cancer is radon exposure and smoking. People who are exposed to both radon and cigarette smoke are at much higher risk of developing lung cancer than non-smokers who have been exposed to the same levels of radon. The particles of cigarette smoke contain at least 3,500 individual compounds such as nicotine, formaldehyde, and polycyclic aromatic hydrocarbons (PAHs). Polycyclic aromatic hydrocarbons (PAHs) are believed to be major contributors to lung cancer risk in smokers.
Comment: Concern about contaminated water from the power plant flowing towards residential areas. Specifically; 1) the movement of surface water from the power plant up gradient in drainage ditches away from the church and swamp toward villages to the east; and 2) surface water moving from multiple locations though the village of Toto.
Response: According to representatives from Guam EPA and Guam Coastal Management, investigations focusing on exactly where water from the power plant property currently flows and historically flowed near Agana Power plant and the locations down slope have not been conducted. Since there is limited detailed information about surface water flow patterns during heavy rain events ATSDR cannot make definitive statements about whether water flowing from the power plant could possibly transport site-related contaminants to residential areas located within the Mongmong-Toto-Maite district.
However, following discussions with residents who live in close proximity to Agana Power Plant, ATSDR revisited the site. Specifically, ATSDR looked at the area in front of the power plant along Roy Damian Road taking photographs and evaluating the topography. Photos with arrows showing the general direction of water movement are provided on the next page. ATSDR noted that the crest of the hill would act as a drainage divide for the road. The water coming off of yards or between the crest of the hill and the Agana Power Plant would flow toward the plant and Agana harbor or toward Agana Swamp. Water from village yards at the top of the hill or over the crest of the hill would generally move toward the swamp or Toto. Therefore, it does not appear that water from the power plant would move over the crest of the hill impacting residential areas in Toto.
Additionally, the Navy collected soil samples from residential properties in close proximity to the power plant. The levels of PCBs were very low and at levels that would not be a concern for adults or children who came in contact with the soil. Large volumes of surface water flowing away from the power plant would result in significant dilution by mixing any site-related contamination with cleaner soil or sediment. Navy investigations showed mostly low levels of PCBs and other contaminants in surface soil and groundwater on site and, therefore, any off site transport of contaminants would be expected to be minimal and not pose any harm to those living in the neighboring residential areas. Guam EPA is aware of these community concerns and can be contacted for additional information.