Some of the pilot study results are attached as Attachment 4. This study will provide specific information on the impact of outdoor sources of air toxics to personal exposures for residents living close to ambient source concentrations. Future Research Directions Only by understanding the relationship among outdoor, indoor and personal exposures can public health impacts be assessed. Additional research on the relationship among outdoor, indoor and personal exposure needs to be conducted. While an exposure research program exists for particulate matter, there is no such overall integrated program for the 188 air toxics listed in Section 112 of the Act.
Exposure is the link between ambient air concentrations and public health impacts.
It is personal exposure to air pollutants, and not air concentration that is the critical component in assessing the public health impacts from air pollutants. Science has now established that indoor air pollutants can be a major contributor to a person's overall exposure to air pollutants. In addition, the findings from these studies indicate that the same air pollutants subject to regulation under the Clean Air Act are often found at much higher levels indoors. The Clean Air Act Amendments of 1990 rely solely on the assumption that outdoor levels are determinative of an individual's exposure and hence risk. The Act does not address the contribution of indoor sources of air pollution or the differences between indoor and outdoor quality.