At a meeting of the EPA Science Advisory Board on Jan. 20, the EPA presented draft revisions to its risk assessment guidelines that were proposed in May 1996.
According to the draft revisions, substances could be classified as human carcinogens if:
- Human studies provide evidence of carcinogenicity, but less than a causal association;
- Animal studies provide strong evidence of carcinogenicity;
- There is a known mode of carcinogenic action and associated key events in animals; and
- the same key events preceding carcinogenicity observed in animals are observed in humans.
Essentially this means that substances could be classified as "known human carcinogens" based solely on animal data. Current risk assessment guidelines require that human evidence demonstrate a causal association -- meaning a convincing body epidemiology.
Dioxin, for example, -- a carcinogen in some animal species, but not in humans -- would be slam dunk for classification as a human carcinogen.
When the EPA initially proposed its revised risk assessment guidelines, I noticed the requirement that epidemiologic studies be statistically significant had been deleted. The EPA deleted this requirement because it was a major stumbling block to classifying substances as human carcinogens.
I brought this to the attention of the Science Advisory Board during the SAB's review of the draft guidelines. The SAB, in a letter, to administrator Carol Browner told the agency to re-insert the requirement of statistical significance.
Now, the EPA has figured out how to get around the requirement -- get rid of the need for epidemiology.
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