Adequate Uncertainty Factor for Exposure Limit
Brian C. Lee
bclee at access2.digex.net
Thu Oct 19 00:58:41 EST 1995
A liver carcinoma is considered benign? What kind of cell type was it?
25-fold sounds pretty low. Was there any human exposure data to show
a non-carcinogenic exposure level?
Lawrence Segal (am879 at FreeNet.Carleton.CA) wrote:
: I am currently reviewing information concerning a proposed occupational
: exposure limit for an industrial chemical. The substance is a
: non-genotoxic carcinogen, which has been tested in both mouse and rat
: chronic/onco studies. In males of both species, statistically significant
: increases in liver adenomas/carcinomas were observed at exposure levels of
: 75 ppm. The company that manufactures the substance is proposing a TWA
: occupational exposure limit of 3 ppm. This provides a 25-fold
: uncertainty factor applied to the LOEL in the rodent studies. The company
: considers this to be an adequate safety factor, because the liver tumours
: were benign, there was no significant increase in mortality at 75 ppm
: relative to control, and the latency period was long.
bclee at access.digex.net brian.lee at woodlawn.com
Miscellaneous Et Cetera Potomac, MD USA
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