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David Mackie,¹ Junfeng Liu,¹ Yeong-Shang Loh,² and Valerie Thomas³

¹Woodrow Wilson School of Public and International Affairs, ²Department of Physics, and ³Princeton Environmental Institute, Princeton University, Princeton, New Jersey, USA

Abstract

The U.S. Environmental Protection Agency (EPA) has developed an estimate of the human cancer risk from dioxin, using the standard low-dose linear extrapolation approach. This estimate has been controversial because of concern that it may overestimate the cancer risk. An alternative approach has been published and was presented to the U.S. EPA Science Advisory Board's Dioxin Review Panel in November 2000. That approach suggests that dioxin is a threshold carcinogen and that the threshold is an order of magnitude above the exposure levels of the general population. We have reexamined the threshold analysis and found that the data have been incorrectly weighted by cohort size. In our reanalysis, without the incorrect weighting, the threshold effect disappears. Key words: cancer, dioxin, TCDD, threshold. Environ Health Perspect 111:1145-1147 (2003) .