Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form


"By denying scientific principles, one may maintain any paradox." – Galileo Galilei

Why is IARC Dictating California Policy?

The state of California announced last month that it will officially list glyphosate as a chemical known to cause cancer today, July 7th. This action is mandated by a Proposition 65 labor code provision, which requires any chemical or substance which may expose a person to a substance classified by the International Agency for Research on Cancer (IARC) as “possibly carcinogenic,” “probably carcinogenic,” or “carcinogenic” be added to the Prop. 65 list of chemicals known to cause cancer. It also requires that they carry a warning label to inform Californian consumers of the presence of the substance.


Given the fact that IARC’s highly flawed carcinogenic evaluation process has come under scrutiny last month, this action begs an obvious question: Why should IARC be the determinant for automatic listing on Prop 65?


Reuters recently uncovered that its glyphosate Monograph working group chair, Dr. Aaron Blair, withheld data that found no evidence linking glyphosate exposure to cancer incidence while the working group was completing its evaluation. IARC went on to publish an evaluation claiming glyphosate is “probably carcinogenic to humans.” As Reuters succinctly puts it,


“The World Health Organization’s cancer agency says a common weedkiller is ‘probably carcinogenic.’ The scientist leading that review knew of fresh data showing no cancer link – but he never mentioned it and the agency did not take it into account.” (emphasis added)


The data that Dr. Blair withheld comes from the Agricultural Health Study (AHS), which is widely known to be the largest and most comprehensive study ever conducted on pesticide exposure in humans. AHS looked at over 50,000 farmers and their families who had been exposed to glyphosate and found no evidence linking glyphosate to cancer incidence. Not only that, but Dr. Blair is one of the scientists from the U.S. National Cancer Institute (NCI) that actually spearheaded the AHS study – and as Reuters also revealed, he was aware of the updated data since at least 2013.


When challenged on this decision, Dr. Blair claimed the data was not published in time because “there was too much to fit into one scientific paper,” an excuse that was deemed absurd by the St. Louis Post-Dispatch editorial board.


“Wait — there was too much evidence, so it had to be omitted? If that’s true, the agency has some explaining to do.”


Under oath, Blair admitted that had IARC considered the study, it likely would have changed its conclusion on glyphosate: “[the] data would have altered IARC’s analysis.” Yet IARC still told Reuters it will not reconsider its conclusions on glyphosate, which are out of step with every other world regulator that has studied glyphosate.


Unfortunately, IARC’s misleading glyphosate classification has direct policy implications in the U.S.


IARC Primary Factor in California Proposition 65 Labor Code Listings


Regulations implementing Prop. 65’s labor code listing mechanism, found in Section 25904 of Title 27 of the California Code of Regulations, state that IARC’s data and specific classifications is the determining factor for whether a chemical is listed as carcinogenic. From Packaging Law:


The new Section 25904, which became effective Oct. 1, 2015, specifies that a chemical or substance shall be included on the list if it is “…classified by the International Agency for Research on Cancer (IARC) in its IARC Monographs series on the Evaluation of Carcinogenic Risks to Humans (most recent edition), or in its list of Agents Classified by the IARC Monographs, as:

  1. Carcinogenic to humans (Group 1), or

  2. Probably carcinogenic to humans (Group 2A) with sufficient evidence of carcinogenicity in experimental animals, or

  3. Possibly carcinogenic to humans (Group 2B) with sufficient evidence of carcinogenicity in experimental animals. A chemical or substance for which there is less than sufficient evidence of carcinogenicity in experimental animals and classified by IARC in Group 2B shall not be included on the list.”


This new provision to the labor code expanded the original labor code criteria for listing chemicals on Prop 65. According to the Safe Drinking Water and Toxic Enforcement Act of 1986 and corresponding Labor Code Section 6382(b)(1), “substances listed as human or animal carcinogens by the International Agency for Research on Cancer” shall be published on the Prop 65 list. The 2015 provision cited above elaborates on the inclusion criteria to state that any “chemical or substance” shall be added on the list if it has been identified specifically by IARC’s Monographs program as a Group 1, 2A, or 2B carcinogen. Why should California base these decisions on a body and program that failed to consider all relevant data?


Other Prop 65 Listings


Another notable example of a chemical that has been deemed carcinogenic by IARC and is also listed on Prop 65’s list is acrylamide — a chemical that naturally occurs in roasted coffee beans, potato chips, cooked vegetables and baked goods.


The basis for the chemical’s listing on Prop 65 originated in IARC’s 1994 declaration that acrylamide was “probably carcinogenic” despite “inadequate” evidence in humans. To this day, there still is no scientific proof linking acrylamide to cancer in people. Meanwhile, federal regulatory agencies say acrylamide is not harmful in the small doses typically found in table food. According to the U.S. Food and Drug Administration (FDA), Americans should not stop eating foods that are fried, roasted or baked because of their acrylamide levels.


Lisa Halko, a Sacramento lawyer, expands upon Prop 65’s false-alarm list versus the FDA’s approach: “There are better ways to get that information to people than putting a warning on just one theoretical risk. The U.S. Food and Drug Administration has more complete, better targeted information on possible risks.”


This affects more than Californians. Given the difficulty in ensuring unlabeled products with Prop 65-listed ingredients do not end up on store shelves in California, many manufacturers stamp the CA-required warning label on products destined for other states that do not have this requirement. This label causes unnecessary alarm and confusion for many other Americans, thus widening the reach of IARC’s flawed science across our country.


Virtually Every Other Study on Glyphosate Contradicts IARC


The U.S. Environmental Protection Agency (EPA), the European Food Safety Authority (EFSA), the European Chemicals Agency (ECHA), and a joint UN/WHO working group have all determined that glyphosate is not carcinogenic. Additionally, EPA, UN and EFSA have all relied upon the AHS for their glyphosate risk assessments. IARC, however, came to a different conclusion as a result of the agency’s flawed research methodologies, which have been criticized by regulatory bodies such as the EPA in the past. So much for IARC being the so-called “Gold Standard.”


Even before the existence of this critical data became public knowledge via Reuters reporting, EPA’s Cancer Assessment Review Committee criticized IARC’s methodology, saying the monograph included “positive findings from studies with known limitations,” lacked “reproducible positive findings,” and omitted “negative findings from reliable studies” which “may have had a significant bearing on IARC’s conclusion on the genotoxic potential of glyphosate.” EPA’s criticism of IARC’s data sources and research methodology is yet another example of why its determination on glyphosate was a textbook example of an outlier and why the Monograph program is in need of extensive reform.





Recent news that an IARC working group chairman suppressed key data proving glyphosate is not a carcinogen is reason enough to question IARC’s influence in U.S. policy. The fact that that every other credible organization has said there’s no evidence that glyphosate causes cancer clearly illustrates even more that IARC’s Monographs should not be dictating California policy decisions.