Richard Denison, Ph.D., is a Lead Senior Scientist.
It’s been a ridiculously long road to get here, because of the delay tactics of the chemical industry. But yesterday a panel of the National Academy of Sciences (NAS) fully backed the National Toxicology Program’s (NTP) listing of styrene as “reasonably anticipated to be a human carcinogen.”
We have blogged earlier about this saga. In June 2011, after years of delay, the NTP released its Congressionally mandated 12th Report on Carcinogens (RoC), in which it upgraded formaldehyde to the status of “known to be a human carcinogen,” and for the first time listed styrene as “reasonably anticipated to be a human carcinogen.” The chemical industry launched an all-out war to defend two of its biggest cash cows, filing a lawsuit to try to reverse the styrene listing (which it lost), and seeking to cut off funding for the RoC.
In late 2011, the industry managed to get its allies in Congress to slip into the Consolidated Appropriations Act of 2012, without any debate, a rider that mandated NAS to review the styrene and formaldehyde listings in the 12th RoC. Yesterday’s NAS report on styrene is the first installment, with the second one on formaldehyde expected shortly.
The NAS report could not be more supportive of the NTP’s listing of styrene, finding “that ‘compelling evidence’ exists in human, animal, and mechanistic studies to support listing styrene, at a minimum, as reasonably anticipated to be a human carcinogen.” (emphasis added)
The NAS committee both peer-reviewed the RoC listing and conducted its own independent review of the styrene literature – and in both cases found strong evidence to support NTP’s original finding. According to NAS’ release:
The committee that wrote the report found that the listing is supported by “limited but credible” evidence of carcinogenicity in human studies, “sufficient” evidence from animal studies, and “convincing relevant information” in mechanistic studies that observed DNA damage in human cells that had been exposed to styrene.
Note that a chemical can be classified as “reasonably anticipated to be a human carcinogen” if there is sufficient evidence in animals or limited evidence in human studies; in the case of styrene, NAS affirmed that there are both types of evidence.
Moreover, NAS found that the available mechanistic evidence could actually support an even stronger classification of styrene, noting that “a strong argument could be made to support the listing of styrene as a known human carcinogen if data derived from the study of human tissues or cells alone were considered sufficient.”
In the end, the chemical industry managed to buy itself 3 years of delay, and temporarily tarnished the reputation of one of the world’s leading authoritative bodies, one that reaches its conclusions only after an exhaustive scientific assessment process entailing reviews by four separate groups of expert scientists for each chemical.
One can only hope that this sorry episode and waste of public resources will help to expose the narrow self-interest of the industry, which for years it has deceptively sought to wrap in a mantle of sound science. Now we know whose science is sound, and whose isn’t.