Human Health Risk Assessment

Mid-Hudson River
Executive Summary
December 1999

This document presents the baseline Human Health Risk Assessment for the Mid-Hudson River (Mid-Hudson HHRA), which is a companion volume to the baseline Human Health Risk Assessment for the Upper Hudson River that was released by the U.S. Environmental Protection Agency (USEPA) in August 1999. Together, the two risk assessments comprise the human health risk assessment for Phase 2 of the Reassessment Remedial Investigation/Feasibility Study (Reassessment RI/FS) for the Hudson River PCBs site in New York.

The Mid-Hudson HHRA quantitatively evaluates both cancer risks and non-cancer health hazards from exposure to polychlorinated biphenyls (PCBs) in the Mid-Hudson River, which extends from the Federal Dam at Troy, New York (River Mile 154) to just south of Poughkeepsie, New York (River Mile 63). The Mid-Hudson HHRA evaluates both current and future risks to children, adolescents, and adults in the absence of any remedial action and institutional controls, such as the fish consumption advisories currently in place. The Mid-Hudson HHRA uses the most recent USEPA policy and guidance as well as additional site data and analyses to update USEPA's 1991 risk assessment.

USEPA uses risk assessment as a tool to evaluate the likelihood and degree of chemical exposure and the possible adverse health effects associated with such exposure. The basic steps of the Superfund human health risk assessment process are the following: 1) Data Collection and Analysis, to determine the nature and extent of chemical contamination in environmental media, such as sediment, water, and fish; 2) Exposure Assessment, which is an identification of possible exposed populations and an estimation of human chemical intake through exposure routes such as ingestion, inhalation, or skin contact; 3) Toxicity Assessment, which is an evaluation of chemical toxicity including cancer and non-cancer health effects from exposure to chemicals; and 4) Risk Characterization, which describes the likelihood and degree of chemical exposure at a site, the possible adverse health effects associated with such exposure, the quantification of cancer risks and non-cancer health hazards, and a discussion of the uncertainties associated with the risk assessment.

The Mid-Hudson HHRA shows that cancer risks and non-cancer health hazards to the reasonably maximally exposed (RME) individual associated with ingestion of PCBs in fish from the Mid-Hudson River are above levels of concern. Consistent with USEPA regulations, the risk managers in the Superfund program evaluate the cancer risks and non-cancer hazards to the RME individual in the decision-making process. The Mid-Hudson HHRA indicates that fish ingestion represents the primary pathway for PCB exposure and for potential adverse health effects, and that cancer risks and non-cancer health hazards from other exposure pathways are significantly below levels of concern. The results of the Mid-Hudson HHRA will help establish acceptable exposure levels for use in developing remedial alternatives for PCB-contaminated sediments in the Upper Hudson River, which is Phase 3 (Feasibility Study) of the Reassessment RI/FS.

Data Collection and Analysis

USEPA previously released reports on the nature and extent of contamination in the Hudson River as part of the Reassessment RI/FS (e.g., February 1997 Data Evaluation and Interpretation Report, July 1998 Low Resolution Sediment Coring Report, August 1998 Database for the Hudson River PCBs Reassessment RI/FS [Release 4.1], and May 1999 Baseline Modeling Report) and on human health risks for the Upper Hudson River (e.g., August 1999 Volume 2F - Human Health Risk Assessment for the Upper Hudson River). The Ecological Risk Assessment for Future Risks in the Lower Hudson River (Federal Dam at Troy, New York to the Battery in New York City), which is being issued by USEPA concurrently with this report, provided the forecasted concentrations of PCBs in fish, sediments, and river water used to conduct the Mid-Hudson HHRA.

Exposure Assessment

Adults, adolescents, and children were identified as populations possibly exposed to PCBs in the Mid-Hudson River due to fishing and recreational activities (e.g., swimming, wading), as well as from residential ingestion of river water. The exposure pathways identified in the Mid-Hudson HHRA are ingestion of fish, incidental ingestion of sediments, dermal contact with sediments and river water, and residential ingestion of river water. For these exposure pathways, average (central tendency) and RME estimates were calculated using point estimate analyses, whereby an individual point estimate was selected for each exposure factor used in the calculations of cancer risks and non-cancer health hazards. The RME is the maximum exposure that is reasonably expected to occur in the Mid-Hudson River under baseline conditions; the RME is not a worst-case exposure scenario.

Risks and hazards through inhalation of volatilized PCBs were not assessed in the Mid-Hudson HHRA because calculated risks for this pathway were shown to be de minimus (insignificant) in the Human Health Risk Assessment for the Upper Hudson River. Given that concentrations of PCBs found in the sediment and river water in the Mid-Hudson are lower than concentrations in the Upper Hudson, the risks from volatilization also would be expected to be insignificant (and lower) in the Mid-Hudson. Similarly, because the concentrations of PCBs in the Mid-Hudson River are lower than in the Upper Hudson, USEPA determined that a Monte Carlo analysis of cancer risks and non-cancer hazards for the fish ingestion pathway was not warranted for the Mid-Hudson HHRA. An assessment of the exposure and risks from dioxin-like PCBs was not performed because the findings for the Human Health Risk Assessment for the Upper Hudson River showed that the risks for dioxin-like PCBs were comparable to those calculated for total PCBs.

Ingestion of Fish

For fish ingestion, both average (central tendency) and RME estimates were developed for each of the parameters needed to calculate the cancer risks and non-cancer health hazards. Based on the 1991 New York Angler survey of fish consumption by licensed anglers (Connelly et al., 1992), the central tendency fish ingestion rate was determined to be approximately six half-pound meals per year and the RME fish ingestion rate was determined to be 51 half-pound meals per year.

Both cancer risks and non-cancer health hazards to an adult angler and a child were calculated. Population mobility data from the U.S. Census Bureau for the six counties surrounding the Mid-Hudson River (i.e., Albany, Columbia, Dutchess, Greene, Rensselaer, and Ulster) and fishing duration data from the 1991 New York Angler survey were used to determine the length of time an angler fishes in the Mid-Hudson River (i.e., exposure duration). The exposure duration for fish ingestion was 12 years for the central tendency exposure estimate for cancer and non-cancer and 40 years for cancer (7 years for non-cancer) for the RME estimate. Standard USEPA default factors were used for angler body weight. Future concentrations of PCBs in fish were derived from forecasts presented in the Ecological Risk Assessment for Future Risks in the Lower Hudson River, which were then grouped by fish species and averaged over species for the entire Mid-Hudson River. PCB losses during cooking were assumed to be 20% for the central tendency exposure estimate and 0% (no loss) for the RME estimate, based on studies reported in the scientific literature.

Other Exposure Pathways

For the direct exposure scenarios for river water and sediment, the average (central tendency) exposure estimates for adults and young children (aged 1-6 years) were assumed to be one day every other week for the 13 weeks of summer (7 days/year) and for the RME were assumed to be one day per week for the 13 weeks of summer (13 days/year). Adolescents (aged 7-18 years) were assumed to have about three times more frequent exposure, with a central tendency exposure estimate of 20 days/year and an RME estimate of 39 days/year. The risks and hazards due to ingestion of river water for drinking water purposes were evaluated for residents living adjacent to the Mid-Hudson River. The concentrations of PCBs in water and sediment were derived from the Baseline Ecological Risk Assessment for Future Risks in the Lower Hudson River. Standard USEPA default factors were used for certain exposure parameters (e.g., body weight) in the cancer risk and non-cancer hazard calculations for these pathways.

Toxicity Assessment

The toxicity assessment is an evaluation of the chronic (7 years or more) adverse health effects from exposure to PCBs (USEPA, 1989b). In the federal Superfund program, two types of adverse health effects are evaluated: 1) the incremental risk of developing cancer due to exposure to chemicals and 2) the hazards associated with non-cancer health effects, which for PCBs include reproductive impairment, developmental disorders, disruption of specific organ functions, and learning problems. The cancer risk is expressed as a probability and is based on the cancer potency of the chemical, known as a cancer slope factor, or CSF. The non-cancer hazard is expressed as the ratio of the chemical intake (dose) to a Reference Dose, or RfD. The chronic RfD represents an estimate (with uncertainty spanning perhaps an order of magnitude or greater) of a daily exposure level for the human population, including sensitive populations (e.g., children), that is likely to be without an appreciable risk of deleterious effects during a lifetime. Chemical exposures exceeding the RfD do not predict specific diseases. USEPA's Integrated Risk Information System, known as IRIS, provides the primary database of chemical-specific toxicity information used in Superfund risk assessments. The most current CSFs and RfDs for PCBs were used in calculating cancer risks and non-cancer hazards in the Mid-Hudson HHRA.

PCBs are a group of synthetic organic chemicals consisting of 209 individual chlorinated biphenyls called congeners. Some PCB congeners are considered to be structurally similar to dioxin and are called dioxin-like PCBs. USEPA has classified PCBs as probable human carcinogens, based on a number of studies in laboratory animals showing liver tumors. Human carcinogenicity data for PCB mixtures are limited but suggestive. USEPA (1996) described three published studies that analyzed deaths from cancer in PCB capacitor manufacturing plants (Bertazzi et al., 1987; Brown, 1987; and Sinks et al., 1992). Recently, Kimbrough et al. (1999) published the results of an epidemiological study of mortality in workers from two General Electric Company capacitor manufacturing plants in New York State. In September 1999, two Letters to the Editor regarding the Kimbrough et al. (1999) study and a response from Kimbrough et al. were published in the Journal of Occupational and Environmental Medicine. Due to the limitations of the Kimbrough et al. (1999) study identified by USEPA and others, USEPA expects that the findings of the Kimbrough et al. (1999) study will not lead to any change in its CSFs for PCBs, which were last reassessed by USEPA in 1996. The toxicity of PCBs is discussed in detail in the Human Health Risk Assessment for the Upper Hudson River.

Risk Characterization

For known or suspected carcinogens, acceptable exposure levels for Superfund are generally concentration levels that represent an incremental upper-bound lifetime cancer risk to an RME individual of 10^-6 to 10^-4 (USEPA, 1990). Ingestion of fish to an RME individual results in the highest cancer risks of approximately 4 × 10^-4 (4 additional cancers in a population of ten thousand). Ingestion of fish for the average (central tendency) scenario results in an incremental upper-bound lifetime cancer risk to approximately 9 × 10^-6 (9 additional cancers in a population of one million). If it is assumed that a child meal portion is approximately 1/3 of an adult portion, then the RME child risk for ingestion of fish is approximately 1 × 10^-4. Estimated cancer risks for all other exposure pathways are below 10^-6 (i.e., less than one in a million). The cancer risks are based on uniform exposure throughout the Mid-Hudson River (i.e., that the exposure occurs throughout the Mid-Hudson study area).

*Total risk for child (aged 1-6), adolescent (aged 7-18), and adult (over 18).

The evaluation of non-cancer health effects involved comparing the average daily exposure levels (dose) to determine whether the estimated exposures exceed the RfD. The ratio of the site-specific calculated dose to the RfD for each exposure pathway is summed to calculate the Hazard Index (HI) for the exposed individual. An HI of one (1) is the reference level established by USEPA above which concerns about non-cancer health effects must be evaluated.

Ingestion of fish by the RME individual results in the highest value for non-cancer health hazards (HI = 30). Ingestion of fish by the average (central tendency) individual results in an HI of 3. Note that the average daily dose decreases as the exposure duration increases, so the average concentration over a 7-year exposure period used as the RME for non-cancer is greater than the average concentration over the 40-year exposure period used as the RME for the cancer assessment. Even if the average concentration of PCBs in fish over 40 years rather than the average concentration over 7 years is used to evaluate non-cancer health hazards (i.e., 0.8 ppm PCBs instead of 1.3 ppm PCBs), the HI would be 18. If it is assumed that a child meal portion is approximately 1/3 of an adult portion, then the RME child HI for ingestion of fish is 10. Total HIs for the recreational exposure pathways are all significantly less than one. The calculated HIs are based on uniform exposure throughout the Mid-Hudson River (i.e., that the exposure occurs throughout the Mid-Hudson study area).

Uncertainties are inherent in the risk assessment process and may exist in PCB concentrations in environmental media, derivation of toxicity values, and estimating potential exposures. The uncertainties in risk characterization for the Mid-Hudson HHRA are expected to be similar to those found in the Human Health Risk Assessment for the Upper Hudson River.

*Higher of value for child or adolescent, which are both higher than adult for these pathways.

Major Findings of the Mid-Hudson HHRA

The Mid-Hudson HHRA evaluated both cancer risks and non-cancer health hazards to children, adolescents and adults posed by PCBs in the Mid-Hudson River. USEPA has classified PCBs as probable human carcinogens and known animal carcinogens. Other long-term adverse health effects of PCBs observed in laboratory animals include a reduced ability to fight infections, low birth weights, and learning problems. The major findings of the report are:

• Eating fish is the primary pathway for humans to be exposed to PCBs from the Mid-Hudson.
  
• Under the RME scenario for eating fish, the calculated risk is approximately four additional cases of cancer for every 10,000 people exposed. This excess cancer risk is more than 100 times higher than USEPA's goal of protection and within the upper bound of the cancer risk range generally allowed under the federal Superfund law.
  
• For non-cancer health effects, the RME scenario for eating fish from the Mid-Hudson results in a level of exposure to PCBs that is 30 times higher than USEPA's reference level (Hazard Index) of one.
  
• Under baseline conditions, the RME cancer risks and non-cancer hazards for eating fish would be above USEPA's generally acceptable levels for a 40-year exposure period beginning in 1999.
  
• For the fish consumption pathway, central tendency cancer risks lie within the risk range of 10^-6 to 10^-4, and non-cancer hazards under central tendency assumptions fall slightly above the USEPA's reference level (Hazard Index) of one.
  
• Risks from being exposed to PCBs in the Mid-Hudson River through skin contact with contaminated sediments and river water, residential ingestion of river water for drinking water, incidental ingestion of sediments, and inhalation of PCBs in air are significantly below USEPA's levels of concern for cancer and non-cancer health effects.

For information about this page, contact: kluesner.dave@epa.gov