ENVIRONMENTAL ISSUES BREAKFAST
WEDNESDAY, APRIL 10, 2019
7 AM Registration | 7:30-9 AM Program

Effect of Scientific Developments on Risk Assessment Toxicity Factors and Regulatory Limits for Chemical Exposures

Joyce Tsuji, Ph.D., DABT, Fellow ATS, Principal Scientist, Exponent

Increased understanding of chemical toxicity in the past has often resulted in lower (more conservative) regulatory exposure limits to protect public health. More recently, however, additional studies and discoveries on how chemicals cause toxic effects have also led to the understanding that toxicity is lower than assumed based on health-protective default approaches, thereby resulting in less stringent limits.

When assessing cancer risks and regulatory exposure limits, a key assumption is that any chemical that causes cancer in animals or humans has no threshold for risk of cancer, and that the risk at low doses can be proportionately extrapolated from that at high doses. A few recent chemical examples will be presented to illustrate the effects of updated toxicity information on the setting of regulatory toxicity factors and exposure limits, including chloroform, a rodent carcinogen; benzo[a]pyrene, a carcinogenic polycyclic aromatic hydrocarbon; and inorganic arsenic, a high-dose human carcinogen.