Environmental Engineering Reference
In-Depth Information
CHAPTER 12
Risk Evaluation of Mercury Pollution
JOANNA BURGER and MICHAEL GOCHFELD
RISK EVALUATIONS VERSUS FORMAL RISK ASSESSMENT
Risk Evaluation
Formal Risk Assessment
Commonalities of Different Risk-Evaluation Methods
EPA's Reference Dose for Methylmercury
An Example of a Formal Human Risk Assessment
Human Health Safety Guidelines
Ecological Risk Assessment for Mercury
Exposure Assessment
Benchmarks
Hazard Quotients
Toxicity Reference Value
Adverse Effects Levels and Screening Levels
Ecosystem Responses to Mercury
RELATING EXPOSURE TO POSSIBLE HARM TO HUMANS
AND ECORECEPTORS
Hazard Quotient Risk Characterization
Screening Levels
Total Maximum Daily Load
RISK EVALUATIONS AND MERCURY
ADDITIONAL ISSUES FOR RISK EVALUATIONS
FOR MERCURY
Monitoring, Biomonitoring, and Surveillance
Bioindicators
Risk Balancing
ASSESSMENT END POINTS AND MEASUREMENT END POINTS
MERCURY, METHYLMERCURY, AND THEIR EFFECTS
ACCEPTABLE RISK FOR MERCURY
HUMAN HEALTH RISK ASSESSMENT FOR MERCURY
Exposure Assessment
Noncancer End Points and Reference Doses
FUTURE RESEARCH NEEDS
common route of exposure for methylmercury (Rice et al.,
2000; Gochfeld and Burger, 2005; Mahaffey et al., 2009;
chapters 13 and 14), but this is not the only issue of con-
cern for mercury contamination, nor is it the only route of
exposure for people or ecoreceptors. (An ecoreceptor is any
species [microbial, plant, or animal] in an ecosystem, and
usually excludes humans.) There is an abundance of infor-
mation on mercury hazards and risks, including extensive
summaries by the United States Environmental Protection
Agency (USEPA, 1997), the Agency for Toxic Substances
and Disease Registry (ATSDR, 1999), and the New Jersey
Mercury Task Force (NJDEP, 2001). The EPA's Integrated
Risk Information System (USEPA, 1995, 2001a) provides an
extensive review as background for developing its Reference
Dose for methylmercury and other mercury species.
Increasingly the public, governmental agencies, and public
policy makers, as well as health professionals and ecolo-
gists, want to understand the risks that derive from mer-
cury in the environment. The risks are to individuals of a
species, including humans, and to populations, communi-
ties, and ecosystems. The risks can be sublethal as well as
lethal, resulting in altered behavior, impaired reproductive
success and/or lower survival, and eventually decreases in
populations. Toxic effects can be at the biochemical, cel-
lular, or organ level. High levels of methylmercury in indi-
vidual organisms can lead both to detrimental effects on
the individuals themselves, and also to other organisms
that consume them, such as birds and mammals (including
humans) that are higher on the food chain (WHO, 2007).
Many people are familiar with fi sh consumption as the most
