Friday, June 16, 2017

Glyphosate Regulatory Evaluation and the IARC Decision

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  Glyphosate, the active ingredient in the herbicide Roundup, has been used as a non-selective (kills all plants) herbicide since 1970.  It blocks a necessary step in plant metabolism and the plant dies, yet it has lower acute toxicity than table salt to animals. It is inexpensive, and a small amount works well, with rapid turnover in the environment. For this reason it has been widely used in municipal, agricultural and residential applications for decades.  Glyphosate sales increased upon the advent of genetically engineered crops. Some of these crops were engineered with a gene that circumvents the toxic effects of glyphosate on the plant, so the herbicide kills weeds but not the plant itself. The technology has been widely adopted and is popular with farmers.  The chemical has been tested and approved but government agencies all over the globe.  Hundreds of studies have concluded that it is extremely safe when used as directed.  However, there is a movement afoot that has targeted this compound with misinformation, including the claim that it causes cancer.  This is almost exclusively predicated on the decision of the International Agency for Research on Cancer (IARC) that described glyphosate as a "probable carcinogen" based on a few barely significant data points, while ignoring higher-quality data.  Dr. Len Ritter is a Fellow of the Academy of Toxicological Sciences and an Professor Emeritus at the University of Guelph. He is an expert in human toxicology and has followed the glyphosate story for decades.  In this episode of Talking Biotech we discuss the historical assessments of glyphosate safety, the well-described risks, and the IARC decision.