Richard Denison, Ph.D., is a Lead Senior Scientist.
Just last week I blogged that a panel of the National Academy of Sciences (NAS) had fully backed the National Toxicology Program’s (NTP) listing of styrene as “reasonably anticipated to be a human carcinogen.”
Today a separate NAS panel strongly endorsed NTP’s listing of formaldehyde as a “known human carcinogen” in its 12th Report on Carcinogens (RoC). As with styrene, this second NAS panel both peer-reviewed the RoC listing and conducted its own independent review of the formaldehyde literature – and in both cases found strong evidence to support NTP’s listing. See the NAS press release here, which links to the full report.
Recall that both of these NAS reviews were compelled by a rider slipped into the Consolidated Appropriations Act of 2012 by allies of the chemical industry, without any debate. The rider was one front in the industry’s all-out war to defend formaldehyde and styrene, two of its biggest cash cows, which also included an effort to cut off funding for the RoC.
While the industry bought itself some time, the NAS formaldehyde panel’s review of NTP’s listing affirmed both NTP’s conclusion and the rigor of NTP’s scientific review. The panel’s report notes (page 8):
The committee concludes that NTP comprehensively considered available evidence and applied the listing criteria appropriately in reaching its conclusion. The 12th RoC states that “formaldehyde is known to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in humans and supporting data on mechanisms of carcinogenesis.” The committee agrees with NTP’s conclusion, which is based on evidence published by June 10, 2011, that formaldehyde is a known human carcinogen.
And based on its own independent assessment of the literature, the NAS panel concluded (page 13, emphases added):
- There is sufficient evidence of carcinogenicity from studies of humans based on consistent epidemiologic findings on nasopharyngeal cancer, sinonasal cancer, and myeloid leukemia for which chance, bias, and confounding factors can be ruled out with reasonable confidence.
- There is sufficient evidence of carcinogenicity in animals based on malignant and benign tumors in multiple species, at multiple sites, by multiple routes of exposure, and to an unusual degree with regard to type of tumor.
- There is convincing relevant information that formaldehyde induces mechanistic events associated with the development of cancer in humans, specifically genotoxicity and mutagenicity, hematologic effects, and effects on gene expression.
In other words, the panel found that all three streams of evidence used (where available) to evaluate chemicals’ toxicity to people – human epidemiological data, studies in laboratory animals, and mechanistic information – were consistent and strongly support the finding that formaldehyde causes cancer in people. And that it causes multiple types of cancer, at multiple sites in the body, via multiple routes of exposure, and through multiple mechanisms.
With regard to the controversy over whether formaldehyde causes leukemia and other blood-related cancers, the NAS panel noted (page 13, emphasis added):
The committee found clear and convincing epidemiologic evidence of an association between formaldehyde exposure and myeloid leukemia. There may also be an increase of other lymphohematopoietic cancers, although the evidence is less robust. … The mechanistic events that were considered by the committee as relevant to the plausibility of formaldehyde-associated tumors beyond the portal of entry included genotoxicity and mutagenicity, hematologic effects, and effects on gene expression. Overall, in mechanistic studies of experimental animals and exposed humans, the evidence is largely consistent and strong. … The committee concludes that these findings provide plausible mechanistic pathways supporting a relationship between formaldehyde exposure and cancer, even though the potential mechanisms of how formaldehyde may cause such systemic effects are not fully understood. It would be desirable to have a more complete understanding about how formaldehyde exposure may cause systemic effects, but the lack of known mechanisms should not detract from the findings of an association between formaldehyde exposure and myeloid leukemia in epidemiology studies.
In my last post on styrene, I concluded: “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.”