Measurements of Hazardous Air Pollutants in Communities Necessitate Review of Air Quality and Exposure Metrics.

Advancements in observational capabilities have led to exponential increases in the number of compounds measured in air with unknown inhalation exposure guidelines or community health risks. Exposure frameworks try to capture a variety of exposure contexts with a range of guidelines; however, they are largely focused on occupational settings, and the relationship between guidelines is not always clear. Consequently, assessing measured compounds within these guidelines is not straightforward, and the question of whether air is safe is not easily answered. Here, the recommendations and aims of exposure frameworks are reviewed, which inherently drive guidelines and risk tolerance. U.S. and select international ambient air quality and inhalation exposure guidelines are compared, illustrating differences between the exposure frameworks and guidelines. For compounds with available exposure guidelines, this comparison provides order-of-magnitude estimates for protection of public health. To improve on these estimates, exposure frameworks are needed that build on ambient observations, target the most vulnerable community members, and consider real-world exposure durations from days to years.