Glyphosate is the active ingredient in RoundUp, made by Monsanto, and the most widely used herbicide in the world. People have been squirting it for the past 40 years, and the amount sprayed on fields has gone up about 15-fold since the introduction of RoundUp Ready crops, also made by Monsanto, in 1996.

Glyphosate inhibits a metabolic pathway used only by plants, fungi, and bacteria. It is therefore not obviously dangerous for birds, insects, or other animals to consume—any risk of RoundUp use comes from off-target effects. Thus, our EPA and the European Commission have just reapproved the use of glyphosate for the next five years. (RoundUp Ready crops are not planted in Europe, but glyphosate is still used, as it's an effective herbicide.)

In last week's Science, two Dutch scientists—collectively, they have backgrounds in ecology, risk assessment, pharmaceuticals, and genetic modification—have questioned whether this reapproval is such a great decision. They suggest that social factors need to be seriously considered in determining how we use agricultural agents. Glyphosate use has impacts for society that go beyond any physiological effects it may have on humans, and societal factors have not been considered thus far.

Risk and hazard

Some very quick background: in 2015, the International Agency for Research on Cancer, an arm of the World Health Organization, classified glyphosate as “probably carcinogenic in humans.” Glyphosate joins that list along with red meat and drinks hotter than 65oC. For glyphosate, this classification was based on studies in tissue culture demonstrating that it could damage DNA in human cells and on rodent studies indicating that exposure to glyphosate could increase the incidence of some rare tumors in mice and rats.

The Internet promptly freaked out.

But recent scrutiny of the methods used to analyze the data from these animal studies has called the conclusions of those experiments into doubt. And long-term studies of human health records have not uncovered any increase in cancer among humans routinely exposed to glyphosate, like farm workers. The substance thus qualifies as a hazard—meaning that exposure to some amount of it might theoretically cause cancer—rather than a risk, which means that exposure to a given amount has actually been demonstrated to cause cancer.

Glyphosate isn't the only agricultural chemical where risk is complicated. Neonicotinoids, a separate class of chemicals, are the most widely used pesticides in the world. They are used to protect plants grown for food, for energy, and for aesthetics, and they work because they are toxic to all insects—the majority of described life on Earth and the most diverse group of animals. But they're far less toxic to non-insects, like birds and mammals, and thus are approved by the EPA for use on crops grown for human consumption.

The three most commonly used neonicotinoids have just been banned in Ontario and in Europe, where the current Insect Apocalypse was first documented. But the chemicals remain in use everywhere else, and they have been found in soil and water, in addition to plants.

These agents have helped increase and maintain the food supply that the growing human population relies on. And they seem to be safe for us to ingest. But about 200 scientists are still suggesting that this should not be the only factor determining how glyphosate use should be regulated. We are not the only ones living on this planet, after all, and just because these agents don’t directly harm our bodies doesn’t mean they aren’t causing harm.

Risk and regulation

When regulating agricultural chemicals, regulating agencies often only consider human health effects, not environmental ones. The effects of glyphosate potentially leaching from soil into groundwater and drinking water are unknown, and its effects on microbial communities are equally uncertain. And there are suggestions that neonicotinoids are hurting insect species beneficial to us—like bees—and are decreasing global biodiversity. People can debate the merits of biodiversity as an end in and of itself and decide whether it can be sacrificed to maintain an adequate food supply for a growing human population. But, in another perspective, 233 scientists are calling to restrict neonicotinoids, arguing that global environmental factors—not just human health—should be given credence in deciding how, and how much of, these agents are used.

And in addition to any potential environmental effects, there are significant societal effects to the continued use of these compounds. People might not want to use them regardless of their safety. Herbicides' and insecticides' continued use have a couple of ramifications. One is that experts’ continued insistence on their safety won’t sway this population’s views, since that’s not its issue in the first place.

Another is that our wariness could limit their efficacy. If the goal is to grow enough food to feed all of humanity and a chunk of humanity refuses to grow, sell, purchase, or eat food gown using these compounds (for whatever reason), then the compounds are not serving their purpose. Nathaniel Johnson came to a similar conclusion regarding the genetic modification of crops. “If we decide it’s just too culturally fraught to accept genetic modification,” he wrote, “we can survive without it—in the same way that we’d survive without computers. We’d figure something else out!”

Such societal effects have not yet been considered in how these agricultural agents can be used, but scientists and government agencies in Europe are trying to figure out how to do so. Perhaps that’s why they approved glyphosate only for the next five years—and not the more standard 10 to 15.

Science, 2018. DOI: 10.1126/science.aat0567

Science, 2018. DOI: 10.1126/science.aau0432 (About DOIs).