Issues in Human Particulate Exposure Assessment: Relationship between Outdoor,Indoor, and Personal Exposures

The recent review of the National Ambient Air Quality Standard for particuslate matter and the resultant new health-based PM_2.5 standard was in part motivated by findings from epidemiological studies. These studies reported significant associations between adverse health effects and concentrations of ambient particulate matter at levels below the previously existing PM₁₀ standard. Interpretation of these results has been hindered by our relatively poor understanding of the relationship between personal exposures and concentrations in the indoor and outdoor environments. Individuals spend the majority of their time in indoor environments. Therefore, it is important to understand where and how they may be exposed to the contaminants which may be causing the health effects, and which activities place them at a higher risk of exposure to these agents. In addition, since particulate matter is a complex mixture of contaminants, further research is required to examine its formation process, sources, composition, and health effects. Without an improved scientific understanding of these issues, it is difficult to assess whether the new PM_2.5 standard will be implemented, and if so, whether it can be adequately protective of public health.