FRANK MIRER, PhD, CIH, is a professor in the CUNY School of Public Health in New York. He can be reached at (212) 396-7782 or
Fifty Shades of Gray Evolving Approaches to Evidence for Chemical Hazards
In May, the Colombian government announced it would halt spraying of the herbicide glyphosate (sold under the trade name Roundup) on coca fields. Colombia’s announcement followed the International Agency for Research on Cancer’s announcement of Monographs Volume 112 classifying glyphosate as “probably” carcinogenic to humans (Group 2A). I’m not sure of the current status of Colombia’s ban; certainly there will be pushback from the U.S. Drug Enforcement Agency and the chemical companies. But it provides a teachable moment for industrial hygienists to understand the evolving practice of identifying exposures that have the toxic potential to cause cancer. Colombia’s spraying of glyphosate was part of the U.S.-sponsored war on drugs. News stories include pictures that evoke an earlier war: the spraying of Agent Orange herbicide in Vietnam. And since a major selling point for GMO crops is resistance to glyphosate, the label-GMO and anti-label-GMO forces will mobilize, likely provoking another war, in which the chemical industry will be a combatant attacking IARC. A broader issue than the assessment for glyphosate concerns sources and interpretation of data for chemical hazard risk assessment. Each volume of IARC monographs is written by a working group of scientists; the group members eventually meet for more than a week of review, discussion, and voting. The U.S. National Toxicology Program’s Report on Carcinogens (ROC), a parallel program of carcinogen classification, was mandated by Congress in 1978 and produced its first report in 1980; these assessments are developed by staff and then peer reviewed by external experts.
Editor's note: California followed suit in September, announcing its intention to list glyphosate as a carcinogen under Proposition 65.
Opposition to the use of Agent Orange in Vietnam was part of my motivation to move from chemistry to toxicology, and the insecticide parathion was part of my post-doctoral project. And I claim expertise (or at least experience) in this process by serving on two IARC working groups, and on National Toxicology Program (NTP) peer review groups for bioassay reports, the criteria for evaluating those bioassay reports, and the Report on Carcinogens (ROC).
- Frank Mirer
IARC Monographs Volumes 112 and 113 address insecticides and herbicides. They classify lindane as known to be carcinogenic to humans (Group 1); DDT, malathion, and diazinphos as probably carcinogenic (Group 2A); and 2,4-D, tetrachlorvinphos and parathion as possibly carcinogenic (Group 2B). Although few IHs work in agriculture, we are likely to get questions about pesticide use in homes and, regarding glyphosate, on our lawns.
- Frank Mirer