Assess exposure (yes/no) to the total JBB environment, recognizing that the burn pit emissions occurred in the presence of PM and other air pollutants from other sources. This broad definition of exposure can be assessed by comparing the health experience of military personnel deployed at the JBB during the period of burn pit operation to that of military personnel deployed to Iraq and Afghanistan at locations without a burn pit or that of military personnel not deployed to the Middle Eastern theatre during the same time. This approach was used to conduct the short-term health studies described in Chapter 6. Although there are limitations to this approach, it may be possible to find an appropriate unexposed comparison group—preferably another deployed population unexposed to burn pits but exposed to PM and other chemicals identified at JBB from other sources. The recommendation for a nondeployed comparison group is based on the committee’s judgment that pollution in the region from sources other than burn pits may pose greater health risks than burn pit emissions.