When Monsanto started selling glyphosate in 1974, the herbicide appeared to pose little risk to humans and wildlife based on toxicity tests the company commissioned and submitted to regulators. But a growing body of evidence shows that regulators’ assumptions about the safety of glyphosate, commonly sold as Roundup, are based on outdated science, according to a team of environmental and public-health experts in a statement appearing in the journal Environmental Health.
The team includes several notable experts in assessing harmful effects from exposure to environmental chemicals, including Bruce Blumberg, professor of developmental and cell biology at the University of California, Irvine; Frederick vom Saal, professor of biological sciences at the University of Missouri; and Bruce Lanphear, professor of children’s environmental health at Simon Fraser University in Vancouver.
The scientists cite emerging evidence of glyphosate’s potential hazards, its persistence in the environment, and its unanticipated routes of human exposure in their call for an independent assessment to safeguard environmental and public health.
Many glyphosate-based herbicides include other chemicals, which could interact in ways that enhance toxicity. But regulators don’t require testing of the mixtures, the scientists say. What’s more, independent scientists can’t test these mixtures because the ingredients are considered a trade secret.
Because glyphosate kills weeds by targeting a plant protein not found in animals, early risk assessments concluded it would not harm humans or wildlife. Regulators assumed no residue would remain on crops–which would expose humans–because farmers would only use the chemical before planting and after harvest, lest they kill their crops along with the weeds.
But Monsanto genetically engineered Roundup Ready soybeans, corn, and other crops to tolerate the chemical, which allowed growers to apply the herbicides late in the season to facilitate harvest. Now studies are detecting glyphosate residue on harvested crops, the scientists say, which means people could be exposed to the herbicides in their diet.
With growers producing millions of acres of Roundup Ready crops, and contending with glyphosate-resistance in weeds, glyphosate has become the most heavily applied herbicide in the world.
And that raises serious concerns, the scientists say, because evidence from animal and human studies over the past two decades undercuts regulators’ assumptions that glyphosate harms only plants. Glyphosate, and the compounds produced when it breaks down, may in fact target several pathways in animals, leading to a wide range of health problems, including liver and kidney damage, birth defects, reproductive disorders, and impaired nutrient uptake. Even more worrying, the scientists argue, was the reclassification of glyphosate as “probably carcinogenic to humans” by the World Health Organization’s cancer research arm last year.
But many of these effects would probably not be detected under traditional regulatory toxicology tests, which have not kept pace with the latest science, they say.
Based on their review of the potential risks from glyphosate exposure, the scientists call for a “fresh and independent examination” of the herbicide’s toxicity, along with systematic efforts to monitor levels in people, drinking water, and the food supply.
In order to avoid potential conflicts of interest, they say, any new regulatory assessments should be conducted by independent scientists with no stake in the glyphosate market, expected to be worth $8.79 billion by 2019. Studies for the most recent glyphosate risk assessment was provided by a group of 25 agricultural companies seeking to renew their glyphosate registration.