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Alfatoxin and benzene are carconogenic, and this is the major concern for low, chronic doses. They are regulated to the few parts per billion level in food. However, according to, aflatoxin is three to five orders of magnitude more carcinogenic, as evident from the lower doses needed to induce tumors in rodents.

Why are the permissible thresholds similar?

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If this doesn't get any joy here, we can consider moving it to Biology.SE if you want. –  jonsca Feb 17 '13 at 3:47
I suspect that chemophobia may play a role: benzene is PETROLEUM and so must be poison, but aflatoxin is more "natural". –  Kevin Kostlan Feb 17 '13 at 3:56
Well, the social response to chemicals isn't something that either Chemistry or Bio.SE is really in a position to answer, though. I'm just looking at it from a perspective of toxicology possibly being more on topic on Bio. I don't think anyone would have a problem if you want it to remain here. –  jonsca Feb 17 '13 at 3:59
I was going to write off your conjecture as cynical, but there's probably a kernel of truth to it. Most people simply have not heard of aflatoxin, despite the fact that it's virtually the mad cow disease of the peanut world. It's difficult to petition regulatory agencies for tighter controls over something you don't know exists. What gets me is that in the PDF you link, the TD50 for rats is less than 1% of that for mice. What's up with that? –  Richard Terrett Feb 17 '13 at 7:32

1 Answer 1

It is usually assumed that there is no finite threshold below which carcinogens will not exert an effect. Therefore, there may be no safe exposure level below which there is no health risk.

Accordingly, a target value that is based solely on possible health risks (considering exposure over a lifetime, possibly even demanding an adequate margin of safety) would be zero.

Nevertheless, permissible limit values for carcinogens should not be set as low as possible since the exposure should not be reduced as much as possible at all costs. Instead, the potential exposure and limit values should be as low as reasonably achievable taking into account economic factors, other benefits and disadvantages, and the ability to detect and remove contaminants.

Hence, there may be similar limit values for various substances with different carcinogenic potentials. On the other hand, there may be different limit values for one substance depending on the exposure pathway (e.g. for different foodstuffs).

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