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Assessment and Remediation of Contaminated Sediments (ARCS) Program

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Baseline Human Health Risk Assessment: Saginaw River, Michigan, Area Of Concern

Crane, J. L. 1992. Abstract and Table of Contents to "Baseline Human Health Risk Assessment: Saginaw River, Michigan, Area of Concern," EPA-905-R92-008. Athens, Ga.: Environmental Research Laboratory.

by

Judy L. Crane
AScI Corporation
Athens, Georgia 30613

Project Officer
Robert B. Ambrose, Jr.
Environmental Research Laboratory
Athens, Georgia 30613

ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ATHENS, GEORGIA 30613

 

Abstract

The Assessment and Remediation of Contaminated Sediments (ARCS) program, a 5-year study and demonstration project relating to the control and removal of contaminated sediments from the Great Lakes, is being coordinated and conducted by the U.S. Environmental Protection Agency's (EPA) Great Lakes National Program Office (GLNPO). As part of the ARCS program, baseline human health risk assessments are being performed at five Areas of Concern (AOCs) in the Great Lakes region. The Saginaw River, located in east-central Michigan, is one of these AOCs.

In this report, exposure and risk assessment guidelines, developed for the EPA Superfund program, have been applied to determine the baseline human health risks associated with direct and indirect exposures to contaminated sediments in the lower 8 km of the Saginaw River. These risks were estimated noncarcinogenic (e.g., reproductive toxicity, teratogenicity, liver toxicity) and carcinogenic (i.e., probability of an individual developing cancer over a lifetime) effects.


Table of Contents

1. EXECUTIVE SUMMARY
1.1 OVERVIEW
1.2 STUDY AREA
1.3 EXPOSURE ASSESSMENT
1.4 RISK ASSESSMENT
1.4.1 Determination of Risk
1.4.2 Noncarcinogenic Risks
1.4.3 Carcinogenic Risks
1.4.4 Uncertainties

2. INTRODUCTION

3. LOWER SAGINAW RIVER AREA OF CONCERN
3.1 ENVIRONMENTAL SETTING
3.2 WATER QUALITY PROBLEMS
3.3 RECREATIONAL USES
3.4 WATER SUPPLY
3.5 CONTAMINATION OF FISH
3.5.1 Routes of Contamination
3.5.2 Fish Advisories

4. RISK ASSESSMENT FRAMEWORK
4.1 CONCEPT OF RISK
4.2 RISK FRAMEWORK

5. EXPOSURE ASSESSMENT
5.1 INTRODUCTION
5.2 EXPOSURE PATHWAYS
5.3 DATA USED IN THE EXPOSURE ASSESSMENT
5.3.1 Data Sources
5.3.2 Data Review
5.3.3 Data Sets
5.4 EXPOSURE ASSESSMENT
5.4.1 General Determination of Chemical Intakes
5.4.2 Intakes: Ingestion of Contaminated Fish
5.4.3 Intakes: Ingestion of Contaminated Waterfowl

6. TOXICITY ASSESSMENT
6.1 TOXICITY VALUES
6.2 LIMITATIONS

7. BASELINE RISK CHARACTERIZATION FOR THE LOWER SAGINAW RIVER
7.1 PURPOSE OF THE RISK CHARACTERIZATION STEP
7.2 QUANTIFYING RISKS
7.2.1 Determination of Noncarcinogenic Risks
7.2.2 Determination of Carcinogenic Effects
7.3 HUMAN HEALTH RISKS IN THE LOWER SAGINAW RIVER
7.3.1 Typical and Reasonable Maximum Exposures
7.3.1.1 Noncarcinogenic Risks
7.3.1.2 Carcinogenic Risks
7.3.2 Subsistence Food Pathways
7.3.2.1 Subsistence Anglers
7.3.2.2 Subsistence Hunters
7.3.3 Additive Risks

8. CHARACTERIZATION OF QUALITATIVE UNCERTAINTIES
8.1 INTRODUCTION
8.2 QUALITATIVE LIST OF UNCERTAINTIES
8.2.1 Data Compilation and Evaluation
8.2.2 Exposure Assessment
8.2.3 Toxicity Values
8.2.4 Risk Characterization
8.2.5 Summary

REFERENCES

APPENDlX A: Importance of Other Complete Exposure Pathways in the Saginaw River Area of Concern

APPENDIX B: Human Toxicity Estimates for Contaminants Present in the Saginaw River Area of Concern


CHAPTER 1

EXECUTIVE SUMMARY
1.1 OVERVIEW

The Assessment and Remediation of Contaminated Sediments (ARCS) program, a 5-year study and demonstration project relating to the control and removal of contaminated sediments from the Great Lakes, is being coordinated and conducted by the U.S. Environmental Protection Agency's (EPA) Great Lakes National Program Office (GLNPO). As part of the ARCS program, baseline human health risk assessments are being performed at five Areas of Concern (AOCs) in the Great Lakes region. The Saginaw River, located in east-central Michigan, is one of these AOCs.

In this report, exposure and risk assessment guidelines, developed for the EPA Superfund program, have been applied to determine the baseline human health risks associated with direct and indirect exposures to contaminated sediments in the lower 8 km of the Saginaw River. These risks were estimated noncarcinogenic (e.g., reproductive toxicity, teratogenicity, liver toxicity) and carcinogenic (i.e., probability of an individual developing cancer over a lifetime) effects.

1.2 STUDY AREA

This risk assessment covers an area adjacent to the lower 8 km of the Saginaw River as it passes through Bay City, Essexville, and parts of Hampton and Bangor townships before entering Saginaw Bay. This area has a history of water quality problems due to point (i.e., industrial and municipal discharges) and nonpoint (e.g., upstream agricultural runoff) sources of nutrients and contaminants. The extent of contamination and eutrophication in the entire Saginaw River/Bay region led to the International Joint Commission's (IJC) decision to designate this region as a Great Lakes AOC. In response, the Michigan Department of Natural Resources (MDNR) has completed one phase of a remedial action plan (RAP) to identify and implement pollution abatement measures for the Saginaw River/Bay AOC (MDNR, 1988).

High levels of nutrients, heavy metals, polychlorinated biphenyls (PCBs), and in some areas, dioxins, have been measured in different compartments of the Saginaw River (e.g., sediments, water column, and fish). Concentrations of PCBs in excess of 1 mg/kg have been measured in sediments. In addition, fish advisories have been issued against consuming carp and channel catfish from the Saginaw River because of excessive levels of PCBs and dioxins. The transport of these contaminants into Saginaw Bay is of concern, and the Michigan DNR has conducted widespread sampling in the Bay to determine contaminant concentrations in the sediments and fish. However, it was beyond the scope of this risk assessment to estimate human health risks to people using the Bay.

PCBs and other contaminants have been detected in fish (e.g., walleye, yellow perch, carp, and catfish) collected from both the Saginaw River and Bay. Since many species of fish travel between the river and bay, there is some uncertainty as to where the fish accumulated their contaminant burden. Fish collected from the mouth of the Saginaw River during the late 1980B contained higher contaminant concentrations than for similar fish species collected from different points in the Bay. For the purpose of this risk assessment, it was assumed that fish collected from the mouth of the river accumulated most of their contaminant burden from the lower Saginaw River.

Several contact and noncontact recreational activities take place along the Saginaw River, with fishing and boating being the most popular pastimes. Fishing occurs by boat and from shore in the Bay City area; ice-fishing is also a common activity during wintertime. Hunting is another popular sport, with waterfowl hunting taking place in several wildlife refuges near the river.

1.3 EXPOSURE ASSESSMENT

This assessment focused on two pathways by which residents of the lower Saginaw River could be exposed to sediment-derived contaminants: 1) consumption of contaminated fish (i.e., walleye or carp), and 2) consumption of contaminated waterfowl (i.e., mallards and gadwalls). Other exposure pathways were determined to be either incomplete (e.g., ingestion of sediments) or insignificant in terms of risk (e.g., ingestion of surface water while swimming). Swimming does not occur very often in the lower Saginaw River, and there are no beaches in the area.

Only a few species of fish and waterfowl were included in the exposure assessment because of the lack of data for many other species. Walleye were chosen because they are the preferred sport fish in the Saginaw River and could be used to represent a pelagic (open-water) species. Carp were selected because they are generally the most contaminated fish in water bodies due to their benthic feeding habits and high lipid content; carp were used to represent a benthic species. Thus, by examining the estimated risk from consuming either carp or walleye, a range of risk estimates could be determined for a variety of exposure scenarios. In terms of waterfowl consumption, the only available data set containing contaminant levels in wild waterfowl were for two mallards and six gadwalls collected in 1985 from the Saginaw River area; these data sets were combined and used in the exposure assessment.

Noncarcinogenic and carcinogenic risks were estimated for typical, reasonable maximum, and subsistence exposures. Typical (i.e., average) exposures were assumed to occur over a period of 9 years; reasonable maximum (i.e., the maximum exposure that is reasonably expected to occur at a site) and subsistence exposures were assumed to occur over a period of 30 years (USEPA, 1989a). These exposure durations were extrapolated over a period of 70 years for estimating carcinogenic risks. The subsistence pathway was chosen for a small segment of the population that may be relying on the consumption of fish or waterfowl from the area for their main source of protein. For all three exposure scenarios, exposures were determined for each chemical and added for each pathway. In addition, exposures were added across pathways (i.e., consumption of fish and waterfowl) for typical and reasonable maximum exposures; this was not done for the subsistence scenario because subsistence anglers and waterfowl hunters represent two sensitive subpopulations that should be considered separately.

For each of these exposure scenarios, different consumption patterns of fish and waterfowl were assumed to take place (Tables 1.1 and 1.2). These consumptions patterns were based, in part, on recommended values given in EPA Superfund guidance (USEPA, 1989a,b; 1991a) or else on study assumptions.

Several heavy metals and organic compounds were included in the exposure assessment: arsenic, cadmium, copper, mercury, zinc, chlordane, dieldrin, heptachlor epoxide, hexachlorobenzene, PCBs, p,p' dichlorodiphenyl dichloroethane (DDD), p,p' dichlorodiphenyl dichloroethylene (DDE), p,p' dichloridiphenyl trichloroethane (DDT), and styrene. This list was selected for those chemicals detected in fish and waterfowl for which noncarcinogenic and/or carcinogenic toxicity values were available.

1.4 RISK ASSESSMENT

1.4.1 Determination of Risk
Noncarcinogenic effects were evaluated by comparing an exposure level over a specified time period with a reference dose (RfD)[1] derived from a similar exposure period (otherwise known as a hazard quotient (HQ)). Thus, HQ = exposure level/RfD. An HQ value of less than 1 indicates that exposures are not likely to be associated with adverse noncarcinogenic effects. HQ values between 1 and 10 may be of concern, particularly when additional significant risk factors are present (e.g., other contaminants at levels of concern) (USEPA, 1988a). The sum of more than one HQ value for multiple substances and/or multiple exposure pathways is represented by the Hazard Index (HI). This assumption of additivity does not account for any synergistic or antagonistic effects that may occur among chemicals.

Carcinogenic risks were estimated as the incremental probability of an individual developing cancer over a lifetime as a result of exposures to potential carcinogens. This risk was computed using average lifetime exposure values that were multiplied by the oral slope factor[2] for a particular chemical. The resulting carcinogenic risk estimate generally represents an upper-bound estimate, because slope factors are usually based on upper 95th percentile confidence limits. Carcinogenic effects were summed for all chemicals in an exposure pathway as well as for multiple pathways (i.e., ingestion of fish and waterfowl). This summation of carcinogenic risks assumed that intakes of individual substances were small, that there were no synergistic or antagonistic chemical interactions, and that all chemicals caused cancer. The EPA believes it is prudent public health policy to consider actions to mitigate or minimize exposures to contaminants when estimated, upper-bound excess lifetime cancer risks exceed the 10-5 to 10-6 range, and when noncarcinogenic health risks are estimated to be significant (USEPA 1988a).

1.4.2 Noncarcinogenic Risks
Noncarcinogenic risks, as represented by HI, were less than 0.5 for all exposure levels and pathways except for the subsistence consumption of walleye (HI = 1) and carp (HI = 4) (Table 1.3). For the high consumption of walleye, the noncarcinogenic risk was at a borderline level of concern and was due mostly to the additive risk of methyl mercury and copper. For carp, only heptachlor epoxide had a HQ value exceeding one; this chemical has been found to cause increased liver-to-body weight ratio in both male and female beagle dogs. The rest of the subsistence hazard index for carp was attributable to the combined risk resulting from exposure to chlordane, dieldrin, and copper.

Although some of the chemicals detected in these animals do not presently have RfD values (e.g., PCBs), it would be premature to state that no noncarcinogenic risk exists from consuming fish or waterfowl from the lower Saginaw River area under typical and reasonable maximum exposures. The noncarcinogenic risk reported here is an estimated risk based on currently available data and toxicity information and should not be construed as an absolute risk.

1.4.3 Carcinogenic Risks
The estimated, upper-bound carcinogenic risk levels for all pathways and exposure scenarios were at or above concern levels G.e., 10-6 to 10-6 range). In all cases, PCBs accounted for nearly all of the carcinogenic risk. There is a possibility that people who ingest, inhale, or have dermal contact with certain PCB mixtures may have a greater chance of incurring liver cancer; however, this statement is based on suggest evidence rather than on verified data.

These risk estimates may have been overestimated because the only available oral slope factor for PCBs was based on Aroclor 1260. The primary Aroclor mixture detected in fish collected from the Saginaw River resembled Aroclor 1254, while only total PCBs were reported for waterfowl. Since Aroclor 1260 contains more highly chlorinated congeners (as well as potentially toxic coplanar congeners) than Aroclor 1254, these risk estimates may be overly conservative.

In comparison with the typical exposure scenario, carcinogenic risks increased by approximately one order of magnitude for reasonable maximum exposures and by two orders of magnitude for subsistence anglers or hunters. The individual risks from consuming walleye or waterfowl were nearly equivalent for each exposure scenario; in comparison, carp consumption increased carcinogenic risks by an order of magnitude. Although walleye and waterfowl contributed equally to the risks of consuming both of these items, the additive risk of consuming carp and waterfowl was largely due to the risk level for carp.

1.4.4 Uncertainties
Several assumptions and estimated values were used in this baseline risk assessment that contributed to the overall level of uncertainty associated with the noncarcinogenic and carcinogenic risk estimates. As with most environmental risk assessments, the uncertainty of the risk estimates probably varied by at least an order of magnitude or greater. Uncertainties were addressed in a qualitative way for those parameters and assumptions that appeared to contribute the greatest degree of uncertainty. One of the greatest sources of uncertainty was the assumption that exposure intakes and toxicity values would not change during the exposure duration. This assumed that human activities and contaminant levels would remain the same over the exposure duration, and that toxicity values would not be updated.

____________________

[1] The RfD provides an estimate of the daily contaminant exposure that is not likely to cause harmful effects during either a portion of a persons' life or their entire lifetime (USEPA, 1989a).

[2] Slope factors are estimated through the use of mathematical extrapolation models for estimating the largest possible linear slope (within 95% confidence limits) at low extrapolated doses that is consistent with the data (USEPA, 1989a).

CHAPTER 2
Introduction

The 1987 amendments to the Clean Water Act, in Section 118(c)(3), authorize the U.S. Environmental Protection Agency's (EPA) Great Lakes National Program Office (GLNPO) to coordinate and conduct a 5-year study and demonstration project relating to the control and removal of contaminated sediments from recommended areas in the Great Lakes region. To achieve this task, GLNPO has initiated the Assessment and Remediation of Contaminated Sediments (ARCS) program. The overall objectives of the ARCS program (USEPA, 1991b), for selected Areas of Concern (AOCs), are to:

  1. Assess the nature and extent of contaminated sediments,
  2. Evaluate and demonstrate remedial options (e.g., removal, immobilization, and advanced treatment technologies) as well as the "no action" alternative,
  3. Provide risk assessments for humans, aquatic life, and wildlife exposed to sediment-related contaminants, and
  4. Provide guidance on the assessment of contaminated sediment problems and on the selection and implementation of necessary remedial actions in the Areas of Concern and other locations in the Great Lakes.

As one part of the ARCS program, baseline human health risk assessments are being prepared for five AOCB: Ashtabula River, OH; Buffalo River, NY; Grand Calumet River/Indiana Harbor Canal, IN; Saginaw River, MI; and Sheboygan River, WI (Figure 2.1). The objectives of these risk assessments are to: 1) estimate the magnitude and frequency of human exposures to contaminants in the AOC, and 2) determine the risk of adverse effects resulting from both typical and reasonable maximum exposures (i.e., the highest exposure that is reasonably expected to occur at a site) to contaminants. Risk estimates are determined for both noncarcinogenic (i.e., chronic or subchronic effects) and carcinogenic (i.e., probability of an individual developing cancer over a lifetime) effects resulting from direct and indirect exposures to sediment-related contaminants.

This document presents a baseline human health risk assessment for one portion of the Saginaw River/Bay AOC (Figure 2.2), the lower 8 km of the Saginaw River. This section of the Saginaw River was chosen because: 1) the site is located in an urban area (Bay City) bisected by the Saginaw River and lies adjacent to Saginaw Bay; 2) several industrial and municipal wastewater treatment plants discharge treated effluent into the river; 3) high levels of contaminants, especially PCBs, have been measured in the river sediments; 4) several recreational areas and marinas are located along the river; and 5) contaminant modeling for another task of ARCS (i.e., the comparative risk assessment) is to be conducted in the same region.


REFERENCES [for Chapter 1--Executive Summary]

MDNR, 1988. Michigan Department of Natural Resources Remedial Action Plan for Saginaw River and Saginaw Bay Area of Concern. September 1988. Michigan Department of Natural Resources Surface Water Quality Division, Great Lakes and Environmental Assessment Section, Lansing, MI.

USEPA, 1988a. Risk Management Recommendations for Dioxin Contamination at Midland, Michigan. Final Report. EPA Region 5, Chicago, IL. EPA-905/4-88-008.

USEPA, 1989a. Risk Assessment Guidance for Superfund: Human Health Evaluation Manual Part A. Interim Final. OSWER Directive 9285.7-01a.

USEPA, 1989b. Exposure Factors Handbook. Office of Health and Environmental Assessment, Washington, DC. EPA/600/8-89/043.

USEPA, 1991a.Risk Assessment Guidance for Superfund. Volume I: Human Health Evaluation Manual. Supplemental Guidance: "Standard Default Exposure Factors." Interim Final (March 25, 1991). OSWER Directive 9285.6-03.


LIST OF FIGURES

Figure


LIST OF TABLES

Table

1.1 Amount of Fish Assumed To Be Consumed per Person per Day from the Saginaw River for each Exposure Scenario

1.2 Amount of Waterfowl Assumed To Be Consumed per Person per Year from the Saginaw River Area for each Exposure Scenario

1.3 Estimated Noncarcinogenic and Carcinogenic Risks to People Residing in the Lower Saginaw River Area

5.1 Potential Pathways by which People May Be Exposed to Contaminants from the Lower Saginaw River

5.2 Complete Exposure Pathways in the Lower Saginaw River

5.3 Mean Contaminant Concentrations in Walleyes (Skin-On-Fillets) Collected from the Mouth of the Saginaw River

5.4 Mean Contaminant Concentrations in Carp (Skin-Off-Fillets) Collected from the Mouth of the Saginaw River.

5.5 Mean Contaminant Concentrations in Waterfowl Collected from the Saginaw River Area

5.6 Generic Equation for Calculating Chemical Intakes (USEPA, 1989a)

5.7 Equation Used to Estimate Contaminant Intakes Due to Ingestion of Fish or Waterfowl

5.8 Parameters Used in Estimating Contaminant Intakes Due to Ingestion of Fish in the Lower 8 km of the Saginaw River

5.9 Parameters Used in Estimating Contaminant Intakes Due to Ingestion of Waterfowl in the Lower Saginaw River Area

6.1 EPA Weight-Of-Evidence Classification System for Carcinogenicity (USEPA, 1989a)

6.2 Human Health Risk Toxicity Data for Chemicals of Interest in the Lower Saginaw River

7.1 Risk Associated with the Consumption of Walleye from the Lower Saginaw River Based on Typical Exposure Levels

7.2 Risk Associated with the Consumption of Carp from the Lower Saginaw River Based on Typical Exposure Levels

7.3 Risk Associated with the Consumption of Waterfowl from the Lower Saginaw River Based on Typical Exposure Levels

7.4 Risk Associated with the Consumption of Walleye from the Lower Saginaw River Based on Reasonable Maximum Exposure Levels

7.5 Risk Associated with the Consumption of Carp from the Lower Saginaw River Based on Reasonable Maximum Exposure Levels

7.6 Risk Associated with the Consumption of Waterfowl from the Saginaw River Area Based on Reasonable Maximum Exposure Levels

7.7 Risk Associated with the Consumption of Walleye from the Lower Saginaw River for Subsistence Anglers

7.8 Risk Associated with the Consumption of Carp from the Lower Saginaw River for Subsistence Anglers

7.9 Risk Associated with the Consumption of Waterfowl from the Saginaw River Area for Subsistence Hunters

7.10 Summary of Noncarcinogenic and Carcinogenic Risks in the Lower Saginaw River


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