Assessing Chemical Exposures during Military Deployments

Military Medicine,  Feb 2004  by Hauschild, Veronique D,  Lee, Arthur P

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Example MEGs and Application

In addition to providing the MEG values, TG 230 provides guidance and example scenarios to demonstrate how to use the information in standard military risk management terms. Several different deployment scenarios from wartime to peacekeeping support operations are presented. These example scenarios do not establish the only way risk decisions can be made but address the different parameters that should be considered when evaluating chemical exposure health risks.

One example scenario is a reconnaissance team establishing a site for a future base camp. Benzene was detected at concentrations averaging 5 mg/m^sup 3^ in several air samples around a factory being considered for temporary living quarters. Table II summarizes the information relative to health effects and MEGs for benzene air exposures available in TG 230. The following paragraphs describe the ORM risk characterization process.

Determine Hazard Probability

In this example, the benzene concentrations are below the 1-hour MEGs so one can assume there is not an immediate or severe health hazard. However, the concentrations exceed the 1-year, the 1- to 14-day, and the 8-hour MEGs. One may assume that in this scenario service members may be exposed for a long duration and quite frequently if used as housing quarters. It is also likely that these personnel would not notice that they were being exposed and thus not try to avoid exposure because the concentrations are below odor thresholds. As a result, the probability of exposure at or above these MEGs can be categorized as "frequent" on the probability scale in Table I.

Determine Hazard Severity

The significance of exceeding these MEGs is based on the levels of health effect severity and medical impact as summarized by Table III. In comparison to the hazards severity definitions in Table III, the health effects from benzene exposures described in Table II can be categorized as "negligible" severity (mild and of minimal operational impact) at the measured concentrations.

Determine Risk Estimate and Confidence

The risk estimate is determined by combining the hazard severity and hazard probability using the risk assessment matrix in Table I. In this example, a "negligible" severity and a "frequent" probability results in "moderate" risk. The confidence associated with this estimate is determined based on the quality of the field/sample data, site-specific exposure information, and toxicity data. The confidence was low in this case because the air samples were only taken once on a single day. A summary of the information that could be presented to a commander relative to this assessment is presented in Table IV.

Implications

Identification and assessment of health risks associated with chemical exposure is clearly an important requirement in today's deployment operations. However, it is not an exact science and requires professional judgment. The use of TG 230 requires a basic understanding of toxicological and industrial hygiene concepts that are taught to preventive medicine officers at the U.S. Army Medical Department Center and School. ORM training using TG 230 is also incorporated into the curriculum. The information provided in TG 230 will allow the medical staff to provide relevant information to commanders about chemical risks.