concentrations in air, water, and soil at which certain adverse health effects might begin to occur in an exposed population. Documentation of how MEGs were derived for specific chemicals is provided in Reference Document 230 (RD-230).


The National Research Council (NRC) was asked to independently review TG-248, TG-230, and RD-230 for their scientific validity, completeness, and conformance to current risk-assessment practices. The NRC assigned this task to the standing Committee on Toxicology and convened the Subcommittee on Assessing Toxicological Risks to Deployed Military Personnel. The subcommittee was asked to review the Army’s documents and to identify deficiencies and make recommendations for improvements. The subcommittee was asked to focus specifically on the following issues:

  1. The Army’s risk assessment, hazard-ranking, and risk-management processes described in TG-230 and its supporting documents.

  2. The use of pre-existing exposure guidelines developed by the NRC and other agencies and organizations and the hierarchical scheme used by the Army in selecting from those various guidelines.

  3. The Army’s approaches to deriving MEGs for criteria pollutants, lead, soil contaminants, and other chemical contaminants.

  4. Technical aspects of the Army’s risk-management framework (as presented in TG-248) regarding competing health risks from different chemicals.

  5. The assumption that the military population includes susceptible subpopulations (e.g., personnel with unknown health conditions, asthma, undetected pregnancies in the first trimester) and the use of uncertainty factors in the derivation of MEGs.

  6. The adjustments of exposure guideline values to account for differences in exposure durations in the derivation of MEGs.

  7. The exposure assumptions and mathematic models used for the derivation of MEGs for air, water, and soil contaminants.

  8. Technical aspects of the Army’s acceptable cancer risk level of 1 in 10,000.

  9. The balance of emphasis between health effects that are produced immediately or soon after exposure and possible delayed effects (e.g., cancer) in the derivation of MEGs for chemical warfare agents and toxic industrial chemicals.

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