Acetaldehyde the first metabolite of ethanol has the largest carcinogenic potency
We estimate carcinogenic potency
by fitting a dose-response function to tumor incidence data from groups of 50 inbred rodents--or from somewhat larger groups of working-age people--and simply pronounce the group potency estimate relevant for hundreds of millions of outbred humans, who among them exhibit every conceivable genetic polymorphism, co-exposure, psychological stress factor, and disease status that is deliberately engineered out of the laboratory or attenuated in the epidemiological raw material.
But I believe we should also expect scientists who are public servants to resist the temptation to go along to get along by accepting more and more "underconfidence" uncritically For example, the Environmental Protection Agency has always declined to quantify the uncertainty around its estimates of carcinogenic potency
, preferring to present a single "plausible upper bound" number but to always surround it with the caveat that the potency "could be as low as zero"--whether or not that deflating verbal hedge has any reasonable basis in theory or evidence.
As it had with previous NATAs, EPA noted that there is a potential cancer risk from diesel PM, but that the available data is inadequate to support a quantitative estimate of the carcinogenic potency
of diesel PM.
But the carcinogenic potency
of mice exposed to dioxin is perhaps 10 million times the carcinogenic potency
of rats exposed to saccharin, whereas for the same chemical the potencies usually agree to within a factor of 10.
of stilbestrol and estrone on strain C3H mice.
Using US Environmental Protection Agency data as a guide for carcinogenic potency
it showed that these chemicals are accountable for 2% of the lung cancer risk associated with smoking cigarettes.
Lois Swirsky Gold, who directs the Carcinogenic Potency
Database at the University of California, Berkeley, says that she isn't convinced that the data reflect an increase in tumors with dose.
Authors Bruce Ames (who developed the "Ames test" used to identify carcinogens) and Lois Gold (director of the Carcinogenic Potency
Project at the National Institute of Environmental Health Sciences Center) point out that naturally occurring rodent carcinogens have been identified in a long list of ordinary food and drink, including lettuce and tomatoes; potatoes and corn; broccoli, cabbage, and peas; hamburgers; orange juice and chocolate milk; black pepper; wine and beer; and common tap water.
For instance, the Carcinogenic Potency
Database (Gold 2010) includes results from chronic, long-term animal cancer tests with mice, rats, and hamsters amounting to a total of 6,540 individual experiments with 1,547 chemicals; 751 of those chemicals (51%) have positive findings in rodent studies.
Gold, director of the Carcinogenic Potency
Project at the University of California, Berkeley.