Sediments

Valence state: The combining capacity of an atom or radical determined by the number of electrons that it will lose, add, or share when it reacts with other atoms.

Source: The American Heritage™ Dictionary of the English Language, Fourth Edition
Copyright © 2000 by Houghton Mifflin Company.

free product: A NAPL found in the subsurface in sufficient quantity that it can be partially recovered by pumping or gravity drain.

aerobic: Direct aerobic metabolism involves microbial reactions that require oxygen to go forward. The bacteria uses a carbon substrate as the electron donor and oxygen as the electron acceptor. Degradation of contaminants that are susceptible to aerobic degradation but not anaerobic often ceases in the vicinity of the source zone because of oxygen depletion. This can sometimes be reversed by adding oxygen in the form of air (air sparging, bioventing), ozone, or slow oxygen release compound (e.g., ORC(r)).

Aerobic dechlorination may also occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Cometabolic dechlorination does not appear to produce energy for the organism. At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal. For aerobic cometabolism to occur there must be sufficient oxygen and a suitable substrate which allows the microbe to produce the appropriate enzyme. These conditions may be present naturally but often in the presence of a source area oxygen and a substrate such as methane or propane will need to be introduced.

Adapted from US. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites

anaerobic: Direct anaerobic metabolism involves microbial reactions occurring in the absence of oxygen and encompasses many processes, including fermentation, methanogenesis, reductive dechlorination, sulfate-reducing activities, and denitrification. Depending on the contaminant of concern, a subset of these activities may be cultivated. In anaerobic metabolism, nitrate, sulfate, carbon dioxide, oxidized metals, or organic compounds may replace oxygen as the electron acceptor.

Anaerobic dechlorination also may occur via cometabolism where the dechlorination is incidental to the metabolic activities of the organisms. In this case, contaminants are degraded by microbial enzymes that are metabolizing other organic substrates. Cometabolic dechlorination does not appear to produce energy for the organism. At pilot- or full-scale treatment, cometabolic and direct dechlorination may be indistinguishable, and both processes may contribute to contaminant removal.

Quoted from US. EPA 2006 Engineering Issue: In Situ and Ex Situ Biodegradation Technologies for Remediation of Contaminated Sites

architecture: "Architecture" refers to the physical distribution of the contaminant in the subsurface. Residuals that take the form of long thin ganglia or small dispersed globules provide a larger surface area that will dissolve much faster than if the same amount of liquid were concentrated in a competent pool.

Sources: For purposes of this discussion, a DNAPL source zone includes the zone that encompasses the entire subsurface volume in which DNAPL is present either at residual saturation or as "pools" of accumulation above confining units. In addition, the DNAPL source zone includes regions that have come into contact with DNAPL that may be storing contaminant mass as a result of diffusion of DNAPL into the soil or rock matrix.

source zone: For purposes of this discussion, a DNAPL source zone includes the zone that encompasses the entire subsurface volume in which DNAPL is present either at residual saturation or as "pools" of accumulation above confining units. In addition, the DNAPL source zone includes regions that have come into contact with DNAPL that may be storing contaminant mass as a result of diffusion of DNAPL into the soil or rock matrix.

focal ulceration: The process or fact of a localized area being eroded away.

metaplasia of the glandular stomach: A change of cells to a form that does not normally occur in the tissue in which it is found.

hyperplasia of the glandular stomach: A condition in which there is an increase in the number of normal cells in a tissue or organ.

histiocytic: Degenerative.

duodenum: First part of the small intestine.

microcytic: Any abnormally small cell.

squamous cell papillomas: A small solid benign tumor with a clear-cut border that projects above the surrounding tissue.

squamous cell carcinomas: Cancer that begins in squamous cells-thin, flat cells that look under the microscope like fish scales. Squamous cells are found in the tissue that forms the surface of the skin, the lining of hollow organs of the body, and the passages of the respiratory and digestive tracts. Squamous cell carcinomas may arise in any of these tissues.

jejunum: The middle portion of the small intestine, between duodenum and ileum. It represents about 2/5 of the remaining portion of the small intestine below duodenum.

ileum: The distal and narrowest portion of the small intestine.

squamous: Flat cells that look like fish scales.

metaplasia: A condition in which there is a change of one adult cell type to another similar adult cell type.

ossification: The process of creating bone, that is of transforming cartilage (or fibrous tissue) into bone.

clastogenesis: Any process resulting in the breakage of chromosomes.

neoplastic: Abnormal and uncontrolled growth of cells.

ulceration: The process or fact of being eroded away.

leucocytosis: An elevation of the total number of white cells in blood.

neutrophils: A type of white blood cell.

chromodulin: A small protein that binds four trivalent chromium ions.

biomagnification: The increased accumulation and concentration of a contaminant at higher levels of the food chain; organisms higher on the food chain will have larger amounts of contaminants than those lower on the food chain, because the contaminants are not eliminated or broken down into other chemicals within the organisms.

exencephaly: Cerebral tissue herniation through a congenital or acquired defect in the skull.

everted viscera: Rotated body organs in the chest cavity.

To Be Considered: Documents, such as federal or state guidances, that are not legally binding but may be relevant to the topic in question.

gaining: A gaining surface water body is one where groundwater flows into it.

losing: A surface water body is losing when there is a permeable sediment bed that is not in contact with the groundwater allowing the surface water to seep through it.

fluvial: Of or pertaining to flow in rivers and streams.

lacustrine: Of or pertaining to a lake as in lacustrine sediments—sediments at the bottom of a lake.

lipid: Any class of fats that are insoluble in water.

lipophilic: Able to dissolve in lipids—in this case fatty tissue.

organelles: A part of a cell such as mitochondrion, vacuole, or chloroplast that plays a specific role in how the cell functions and membranes.

RfD: The RfD is an estimate of a daily exposure of the human population (including sensitive sub-groups) to a substance that is likely to be without "the appreciable risk of deleterious effects during a lifetime." An RfD is expressed in units of mg/kg-day.

autonomic: That part of the nervous system that controls non-conscious actions such as heart rate, perspiration and digestion.

ataxia: Lack of muscle coordination.

funnel-and-gate configuration: A system where low-permeability walls (the funnel) placed in the saturated zone direct contaminated ground-water toward a permeable treatment zone (the gate)

References: ATSDR (Agency for Toxic Substances and Disease Registry). 2015. Draft Toxicological Profile for Perfluoroalkyls. 574 pp.

EFSA (European Food Safety Authority). 2008. Opinion of the scientific panel on contaminants in the food chain on perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) and their salts. EFSA Journal 653:1-131.

Hekster, F.M., R.W.P.M. Laane, and P. de Voogt. 2003. Environmental and toxicity effects of perfluoroalkylated substances. Reviews of Environmental Contamination and Toxicology 179:99-121.

Higgins, C. and R. Luthy. 2006. Sorption of perfluorinated surfactants on sediments. Environmental Science & Technology 40(23):7251-7256.

HSDB (Hazardous Substances Data Bank). 2012 Update. Perfluorooctanoic acid.

Kaiser, M.A., B.S. Larsen, C-P.C. Kao, and R.C. Buck. 2005. Vapor pressures of perfluorooctanoic, -nonanoic, -decanoic, -undecanoic, and -dodecanoic acids. Journal of Chemical and Engineering Data 50(6):1841-1843.

Kauck, E.A. and A.R. Diesslin. 1951. Some properties of perfluorocarboxylic acids. Industrial and Engineering Chemical Research 43(10):2332-2334.

Lewis, R.J., Sr., ed. 2004. Sax's Dangerous Properties of Industrial Materials. 11th ed. Wiley-Interscience, Hoboken, NJ. V3:2860.

Lide, D.R. 2007. CRC Handbook of Chemistry and Physics. 88th ed. CRC Press, Boca Raton, FL. 3-412.

SRC (Syracuse Research Corporation). 2016. PHYSPROP Database. SRC Scientific Databases, Accessed May 2016.

UNEP (United Nations Environmental Program). 2015. Proposal to List Pentadecafluorooctanoic Acid (CAS No: 335-67-1, PFOA, Perfluorooctanoic Acid), Its Salts and PFOA-Related Compounds in Annexes A, B and/or C to the Stockholm Convention on Persistent Organic Pollutants. UNEP/POPS/POPRC.11/5.

USEPA (U.S. Environmental Protection Agency). 2016. Drinking Water Health Advisory for Perfluorooctanoic Acid (PFOA).#pdfsmall# Office of Water, EPA 822-R-16-005, 103 pp

• Overview
• Policy and Guidance
• Conceptual Site Models
• Fate and Transport of Contaminants
• Site Characterization
• Risk Assessment
  • Bioavailability, and Bioaccumulation, and Biotransformation
  • Human Health Risk Assessment
  • Ecological Risk Assessment
• Remediation
• Additional Resources

---

• Issue Areas Home
• Suggest Resource

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.

Toxicological Profiles
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

• PCBs
• 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).

Further Reading

ARAMS (Adaptive Risk Assessment Modeling Systems)
USACE

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.

Screening Level Ecological and Human Health Risk Assessment, Poplar Point, Washington, DC
NOAA.

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
Crane, J.L.
Environmental Research Laboratory, Athens, GA, EPA 905/R-92/007, 1992

Baseline Human Health Risk Assessment: Buffalo River, New York, Area of Concern
Crane, J.L.
EVS Consultants, Seattle, WA, EPA 905/R-93/008, 1993

Baseline Human Health Risk Assessment: Saginaw River, Michigan, Area of Concern
Crane, J.L.
Environmental Research Laboratory, Athens, GA, EPA 905/R-92/008, 1992

EPA Radiation Guidance for CERCLA Risk Assessment Guidance (OSWER Directives) Recommended by EPA Superfund Program

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

Report on the Safety of Consuming Fish and Shellfish from Areas Impacted by the M/V Cosco Busan Oil Spill in San Francisco Bay, California

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.

RESRAD
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.

Top of Page