To estimate the health risks from exposures to toxic substances, the DoD adopted a health risk assessment methodology based on that used by the US Environmental Protection Agency. This process, illustrated in Figure D-1, estimates the health risks from exposure to contaminant concentrations and contaminated sites, and the health risks from the contaminant's toxicity characteristics. It consists of four steps: hazard identification, dose assessment, toxicity assessment, and risk characterization.

Figure D-1.  Health risk assessment process

Hazard identification determines who was exposed and how -- including the identification of: a) the possible contaminants (in this case, DU); b) the individuals exposed to that contaminant; c) the exposure pathways (e.g., inhalation); and d) which incidents need to be evaluated. Dose assessment estimates the intensity, frequency, and duration of exposures to DU and what chemical and radiological intakes these doses represent. Toxicity assessment involves researching the medical effects of exposure to DU and at what levels of exposure these effects might start to occur. Risk characterization is the "bottom line" of the health risk methodology. Using both dose-assessment and toxicity assessment data, the risk assessment provides an explanation of the health risk from a given activity or exposure scenario. To arrive at this assessment, the Office of the Special Assistant for Gulf War Illnesses (OSAGWI) developed an investigation and validation process that includes:

• A detailed reconstruction of the events, conditions and circumstances surrounding the various exposure scenarios;
• An evaluation of available, pertinent environmental factors -- e.g., radiological surveys, air quality monitoring, and other appropriate data;
• Eyewitness testimonies;
• A review of operative policies, guidance, and directives in place at the time of the incidents in question;
• A review of actual practices and the compliance with policies, guidance, and directives in force during the events in question, identifying issues not adequately addressed by that guidance;
• A review of the existing body of scientific and medical data relative to known Gulf War exposure conditions and variables;
• The identification of information gaps and essential elements of information;
• A review of the current body of scientific and medical information on the health effects of DU; and
• The preparation of detailed health risk assessments for each of the activities with potential DU exposure.

Performing this assessment for DU involves the cooperative efforts of several organizations:

• The Office of the Special Assistant for Gulf War Illnesses for the hazard identification and risk characterization;
• US Army Center for Health Promotion and Preventive Medicine (USACHPPM) for the exposure and risk assessment; and
• RAND Corporation for the toxicity assessment.

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