Thanks for your question and for permitting us the opportunity to respond to this very important issue. The study that you are referring to is by Thongprakaisang et al. and reports that glyphosate induces the growth of human breast cancer cells via an estrogen receptor–mediated signaling pathway. First, it is very important to clear something up. This study was performed in a laboratory setting with cells. The cells are immortal T47D breast cancer cells derived from an infiltrating ductal carcinoma of the breast. Therefore, this study was performed on already cancerous cells and did not cause breast cancer. The results in no way implicate glyphosate as inducing human breast cancer.
Counter to the findings in this one study, glyphosate does not have estrogenic activity. In fact, the results of this study contradict what is widely established about glyphosate: that it is not an endocrine active compound, an estrogen receptor agonist or carcinogenic. Glyphosate was recently screened in the Environmental Protection Agency's Tier 1 screening battery under the Endocrine Disruptor Screening Program, and, based on the results of the validated EDSP Tier 1 assays, glyphosate did not have estrogenic activity. Additionally, numerous studies in the literature clearly demonstrate that glyphosate is not an estrogen receptor agonist. Williams et al. (2012) performed an analysis of the available literature to assess the developmental and reproductive safety of glyphosate and concluded that “the literature shows no solid evidence linking glyphosate exposure to adverse developmental or reproductive effects at environmentally realistic exposure concentrations.” This includes several studies showing that “glyphosate did not demonstrate estrogenic activity.”
Glyphosate is not carcinogenic. A literature review by Mink et al. concludes that there is “no consistent pattern of positive associations indicating a causal relationship between total cancer (in adults or children) or any site-specific cancer and exposure to glyphosate.” Also, the Environmental Protection Agency classifies glyphosate as a compound that shows no evidence of carcinogenicity for humans.
Glyphosate is one of the most widely used and most comprehensively evaluated active ingredients in herbicides worldwide, and all assessments have consistently concluded that glyphosate does not pose any unacceptable risk to human health, the environment or nontarget animals and plants. Glyphosate’s overall low toxicity and its excellent safety profile are major benefits that have contributed to the widespread use of glyphosate based plant protection products.