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).
Cancer Risk Summary
|
Pathway |
Central Tendency Risk |
RME Risk |
Ingestion of Fish:
Adult
Child |
9 x 10-6 (9 in 1,000,000)
3 x 10-6 (6 in 1,000,000) |
4 x 10-4 (4 in 10,000)
1 x 10-4 (1 in 10,000) |
Recreational Exposure to Sediment* |
2 x 10-8 (2 in 100,000,000) |
2 x 10-7 (2 in 10,000,000) |
Recreational Dermal Exposure to Water* |
9 x 10-9 (9 in 1,000,000,000) |
6 x 10-8 (6 in 100,000,000) |
Consumption of Drinking Water* |
2 x 10-8 (2 in 100,000,000) |
1 x 10-7 (1 in 10,000,000) |
*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.
Non-Cancer Hazard Summary
|
Pathway |
Central Tendency
Non-Cancer Hazard Index |
RME Non-Cancer
Hazard Index |
Ingestion of Fish:
Adult
Child |
3
1 |
30
10 |
Recreational Exposure to Sediment* |
0.002 |
0.004 |
Recreational Dermal Exposure to Water* |
0.005 |
0.007 |
Consumption of Drinking Water* |
0.01 |
0.02 |
*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
|