- Policy and Guidance
- Conceptual Site Models
- Fate and Transport of Contaminants
- Site Characterization
- Risk Assessment
- Additional Resources
Human Health Risk Assessment
Many occupational activities bring adults into contact with chemically contaminated sediment. Subsistence fishermen and clam diggers make skin contact with sediment on nets and other equipment. Persons dredging and handling excavated sediment may touch it while working. Recreational activities, such as swimming, paddling, duck hunting, fishing, and walking, bring both children and adults into direct skin contact with sediment. There is always a possibility of the incidental ingestion of sediment when it is present on a child�s hands, and to a lesser extent, on the hands of adults. Fish and shellfish collected from areas with sediment contamination may have accumulated contaminants in their tissues. When humans consume these shellfish and fish, a possibility exists that the contaminants will bioaccumulate in their tissues and, at a certain level, exert toxic effects. PCBs, PAHs, and PCDDs are all probable human carcinogens and sediment contaminants. The heavy metals—mercury, cadmium, and lead—frequently found in contaminated sediment can cause damage to the central nervous system and kidneys. An accurate assessment of human health risks posed by contaminated sediments is essential due to the nature of the most frequent chemical contaminants.
The most common routes of exposure to sediment-associated contaminants are incidental ingestion of sediment, ingestion of meals prepared with contaminated fish or shellfish, and dermal contact. Although it is possible to inhale volatilized contaminants from the surface of exposed sediments, PCBs, PAHs, PCDDs, and heavy metals are not particularly volatile, so inhalation generally is minimal compared with ingestion and dermal contact. The exposure of the receptor to the contaminant is quantified by combining site-specific concentrations with default values for contact and uptake parameters according to plausible exposure scenarios.
An example of an exposure assessment for contaminated sediment is provided by a recently performed risk assessment of contaminated sediments of the Lower Duwamish Waterway. This risk assessment focused on tribal members fishing in the waterway, people digging clams, children playing in mud, recreational users of the waterway (walking dogs below the high tide line), and people consuming three meals a week of contaminated seafood. Four of these activities resulted in direct contact with sediment, and the fifth with contaminants that bioaccumulate in food.
Lower Duwamish Waterway Superfund Site
Lower Duwamish Waterway Group
This Web page contains, among other things, a draft remedial investigation that has complete human health and ecological baseline risk assessments as appendicies.
Agency for Toxic Substances and Disease Registry (ATSDR).
ATSDR publishes Toxicological Profiles that summarize the health effects, toxicokinetics, physical chemistry, and potential for human exposure for a large number of organic and inorganic chemicals. These profiles are an invaluable source of general and technical information for human health risk-related issues.
Examples of Toxicological Profiles
- ATSDR Toxicological Profile for Mercury, 1999
- ATSDR Toxicological Profile: Polychlorinated Biphenyls (PCBs), 2000
- ATSDR Toxicological Profile: Polycyclic Aromatic Hydrocarbons (PAHs), 1995
- ATSDR Toxicological Profile for Chlorinated Dibenzo-p-Dioxins, 1998
The WHO also provides fate and transport, exposure, and human health risk information in their Concise International Chemical Assessment documents.
Exposure Factors Handbook
USEPA, National Center for Environmental Assessment (NCEA), 1,193 pp, 1997
This handbook provides a summary of the available statistical data on various factors used in assessing human exposure. The standard factors needed for data to calculate human exposure to toxic chemicals include drinking water consumption; soil ingestion; inhalation rates; dermal factors (including skin area and soil adherence factors); consumption of fruits and vegetables, fish, meats, dairy products, homegrown foods, and breast milk; human activity factors; consumer product use; and residential characteristics.
Child-Specific Exposure Factors Handbook
USEPA, National Center for Environmental Assessment (NCEA), EPA 600/P-00/002B, 448 pp, 2002
The Child-Specific Exposure Factors Handbook provides a summary of the available and up-to-date statistical data on various factors for assessing children's exposures
Risk Assessment Guidance for Superfund
The human health risk assessment (HHRA) approach used by Superfund and other EPA waste and cleanup programs is based on the National Academy of Sciences risk assessment paradigm. Each program has adapted the paradigm to accommodate their regulatory drivers. Guidance for the performance of HHRA is provided by the five documents that comprise Risk Assessment Guidance for Superfund (RAGS), Volume I (1989).
RAGS Part A Human Health Evaluation Manual
USEPA, National Center for Environmental Assessment (NCEA), EPA 600/P-00/002B, 448 pp, 2002
Once contaminants of concern in sediment have been characterized and their concentrations determined, toxicity values can be identified for them. Toxicity values are determined for carcinogenic and noncarcinogenic effects. The exposure period for which a toxicity value is required is also identified. For example, is the toxicity value a chronic value, reflecting long-term exposure to the contaminant, or is it an acute toxicity value representing a single or very short-term exposure? The preferred source (US EPA 2003) of human health toxicity values is USEPA's Integrated Risk Information System (IRIS). IRIS contains verified toxicity values for noncancer and cancer effects. IRIS is an EPA database containing Agency consensus scientific positions on potential adverse human health effects that may result from chronic (or lifetime) exposure to chemicals in the environment. IRIS currently provides health effects information on over 500 specific chemical substances.
Example IRIS Summaries
- Methylmercury (MeHg)
- Hexachlorodibenzo-p-dioxin (HxCDD), mixture of 1,2,3,7,8,9-HxCDD and 1,2,3,6,7,8-HxCDD
- Benzo[a]pyrene (BaP)
The HHRA process described by RAGS Part A is driven by chemical or radiological contamination but does not address microbiological contamination; however, a recent risk assessment of the bacterial contamination of the sediments that comprise the mudflats of the Lower Passaic River in Northern New Jersey suggests that pathogen-contaminated sediments near combined sewer overflows could pose a health risk. An analysis of some strains of bacteria, such as Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, indicate that each strain is resistant to at least one antibiotic in general clinical use. Incidental ingestion was the exposure route considered in this risk assessment for exposure scenarios involving a visitor to the mudflats, a recreational user, and homeless person living on the shoreline and collecting trash (Donovan 2008).
Web site that offers a tool for the evaluation of present and future human and ecological health impacts or risks associated with chronic exposure to militarily relevant compounds (MRCs) and other constituents of potential concern.
Documents at this site, including a PowerPoint presentation, give a clear site conceptual model (slide 17) for the initial stage of a HHRA.
Baseline Human Health Risk Assessment Ashtabula River, Ohio, Area of Concern
Environmental Research Laboratory, Athens, GA, EPA 905/R-92/007, 1992
Baseline Human Health Risk Assessment: Buffalo River, New York, Area of Concern
EVS Consultants, Seattle, WA, EPA 905/R-93/008, 1993
Baseline Human Health Risk Assessment: Saginaw River, Michigan, Area of Concern
Environmental Research Laboratory, Athens, GA, EPA 905/R-92/008, 1992
EPA Web site that lists many guidance documents and sources for internet training on radiological issues.
Human Health Risk Assessment: Upper Hudson River. Executive Summary
USEPA Region 2, 1999
An Overview of the oil spill and updates to the wildlife advisories that resulted from the M/V Cosco Busan Oil Spill in San Francisco Bay, California, provides links to factsheets, memoranda, and the updated results of investigations.
U.S. DOE, Argonne National Laboratory
Web site that offers links to training and guidance documents for radiological ERA and HHRA.
The Risk Assessment Information System
U.S. DOE, Office of Environmental Management
Web site that provides HHRA and ERA guidance, regulatory guidance, risk tools, ecological benchmarks, and tutorials.
Risk of Gastrointestinal Disease Associated with Exposure to Pathogens in the Sediments of the Lower Passaic River
Donovan, E.P., D.F. Staskal, K.M. Unice, J.D. Roberts, L.C. Haws, B.L. Finley, and M.A. Harris.
Applied and Environmental Microbiology, Vol 74, No 4, p 1004-1018, 2008
This article describes the microbiological contamination of sediments in the Passaic River Basin and a human health risk assessment of the impact of these contaminants.