The Right Coast

December 13, 2005
Rodent Testing
By Mike Rappaport

Tyler Cowan quotes a defense of animal testing as a means of detecting human carcinogens. It is interesting, but it elides the key issue:

We know of no false negatives with this process. Every chemical we know that causes cancer in humans also does so in rodents (with the possible exception of inorganic trivalent arsenic, which is equivocal). The reverse question, whether everything that causes cancer in animals also is a human carcinogen, is not testable without doing the actual natural experimen: waiting to see if people get cancer on exposure, an experiment ACSH is only too happy to conduct on the American people to make their corporate sponsors happy.
It is interesting that every human carcinogen is a rodent carcinogen, but the real question is whether every rodent carcinogen (at high doses!) is a human carcinogen (at low doses). Or more relevantly, how often redent carcinogens are human carcinogens.

It is not enough to plead ignorance and move on. I am not saying that absent good information, we should necessarily ignore rodent tests. But we should not just assume that they are informative about humans, either.

I would be interested in knowing whether animal carcinogens that are widely used by humans seem to be human carcinogens. It is sometimes said there are 24 carcinogens in coffee. Is there any evidence it is a human carcinogen?