The Developmental and Reproductive Risks Associated with Glyphosate Exposure
Aaron Lobsenz Abstract: Glyphosate is the primary active ingredient in many glyphosate-based herbicides (GBHs) including RoundUp, Touchdown, Glifloglex, and Glyphogan. When GBHs were first introduced to agriculture in the 1970s, they were regarded as harmless to humans. However, recent studies suggest that human exposure to GBHs may be associated with reproductive inhibition. This paper describes glyphosate and GBHs and the risks that they potentially pose to human reproduction and development. Introduction: Plants use the shikitame pathway to synthesize the amino acids tryptophan, phenylalanine, and tyrosine (see Figure 1)1. Glyphosate’s ability to actively inhibit 3phosphoshikimate 1-carboxyvinyltransferase (EPSP synthase) prevents this mechanism.
Figure 1: This diagram depicts the mechanism of the shikimate pathway, which glyphosate and GBHs act upon to inhibit the synthesis of three essential amino acids.
4
Researchers initially believed that GBHs would pose no significant health risks to humans, who do not use this pathway. Because of the increasing usage of GBH resistant crops – to remove unwanted weeds and plants while protecting crops – GBHs’ utilization has significantly increased. Between 1974 and 2014, overall glyphosate use in the United States (US) rose approximately 300-fold in agriculture. Globally, the use of glyphosate increased from 12 to 20 million liters from 2008 to 20122. With its increasing presence in the environment and food supplies, some studies that examined GBHs’ impact on human and animal health are finding concerning results. Varying regulatory bodies have made different determinations regarding its safety. In 2017, the International Agency for Research on Cancer classified glyphosate as “probably carcinogenic” to humans. However, currently, the European Food Safety Authority and the US Environmental Protection Agency both consider glyphosate to pose no significant risks2. Glyphosate Persistence in Humans: Glyphosate is frequently found within human urine, blood, and maternal milk, which primarily accumulates in the kidneys, liver, colon, and small intestine. Glyphosate in urine is detected at a rate of 0.16-7.6 µg/L in the general population, 0.26-73.5 µg/L in exposed workers, and up to 292 µg/L in workers in China involved in glyphosate production. One of the few studies that directly tested glyphosate on humans discovered that it could remain in the body for at least 106 hours after initial consumption. The same study also found that, in comparison to prior animal studies, less glyphosate is removed from urine in humans than in animals, raising possible concerns over bodily absorption rate and lingering presence of glyphosate in humans3.
