Glyphosate and human health: Response to correlation accusations
Some recent articles (two authored by Samsel and Seneff1 and one by Nancy Swanson2) attempt to establish causal links between glyphosate and a range of diseases and health conditions in humans.
A common theme evident in these publications is the presentation of glyphosate as a causal factor (or at least one link in a chain of causal factors) related to numerous diseases and conditions including autism, Alzheimer’s, obesity, anorexia nervosa, liver disease, reproductive and developmental disorders and even cancer.
© iStockphoto.com/Aseev However, these publications do not present any new data and are of limited value as they are restricted to hypothetical speculation on various matters.
The most recent paper (Swanson et al) links numerous observations in an attempt to establish a chain of causation connecting glyphosate to various health issues. However, many of the individual observations made are either incorrect or poorly established. None of the disease associations are supported by available toxicology testing or observations which associate glyphosate exposure with these disease outcomes in human populations.
In short, the authors have put forth a series of highly elaborate hypotheses regarding causation in the absence of any observable associations. In the event that any single one of the assumptions or linkages in the overall string of hypotheses is incorrect, the entire hypothesis fails. Furthermore, the authors’ approach fails to consider other hypothetical causes even though biological systems are highly complex.
In fact, previous risk assessments have established that glyphosate has a low degree of mammalian toxicity. One of the reasons for this is that it targets a metabolic pathway which although present in plants does not occur in animals. Comprehensive toxicological studies in animals have demonstrated that glyphosate does not cause cancer, birth defects, mutagenic effects, nervous system effects or reproductive problems3.
After a thorough review of all toxicology data available, the U.S. EPA concluded that glyphosate should be classified in Category E (“Evidence of Non-carcinogenicity in Humans”), the most favourable category possible4. Moreover, numerous health assessments conducted by public authorities over the past 40 years have so far concluded that glyphosate does not pose any unacceptable risk to human health.
3 U.S. EPA, 1993; Williams et al., 2000; Williams et al., 2012; Kier and Kirkland, 2013; European Commission, 2002; JMPR, 2004.
Last update: 21 April 2015