The findings of a new study indicates that exposure to glyphosate-based weedkillers like Roundup may harm the organisms that are central to the food web of aquatic ecosystems, which could have an adverse impact on the food chain and potentially cause problems for other species. Originally developed by Monsanto in the 1970s, Roundup is the world’s most widely used non-selective herbicide, with six billion kilograms applied to farms, orchards and residential lawns and gardens worldwide. Unfortunately, Roundup is widely understood to pose a possible adverse human health risk to those who come in contact with the weedkiller, as well as a significant risk to livestock, wildlife and even aquatic ecosystems in areas where runoff from farms and residential neighborhoods flows into nearby rivers, streams and lakes. This Roundup contamination can in turn have an adverse impact on the animals and plant life that depend on these fragile habitats for survival.
In the decades since Roundup was introduced, the weedkiller has become popular for use in both commercial and residential settings because of its ability to destroy weeds without harming crops or killing grass. However, the safety of glyphosate was called into question in 2015, when the World Health Organization’s (WHO) International Agency for Research on Cancer (IARC) classified the chemical as a probable human carcinogen. Research has since established a potential link between Roundup’s active ingredient, glyphosate, and non-Hodgkin’s lymphoma, as well as certain other cancers. More recently, important questions have been raised about the impact of widespread Roundup use on human health and the environment, particularly the ecosystems in areas where the weedkiller is routinely applied.
In this latest study, published in the journal Microbiome on December 15, 2020, researchers from the United Kingdom looked at the impact of glyphosate exposure on Daphnia, also known as water fleas, a keystone species in ponds, lakes and other freshwater environments around the world. Daphnia are planktonic crustaceans. They eat algae, bacteria and other primary producers and are eaten by tadpoles, newts, salamanders, aquatic insects and certain types of small fish. Daphnia are vital to aquatic food chains and fluctuations in populations can lead to issues like algae overgrowth or can even cause a dramatic drop in fish populations. And these changes can travel up the food chain and have an impact on larger animals that are caught or eaten by humans.
Because Daphnia hold an important position in aquatic food chains and are extremely sensitive to changes in their environment, they are widely utilized as an indicator species to gauge the response of ecosystems to environmental stress. What the researchers in this study found is that chronic exposure to concentrations of the weedkiller glyphosate at the threshold federal regulators have approved for drinking water in the United States can “induce embryonic developmental failure, induce significant DNA damage (genotoxicity), and interfere with signaling.” The researchers also found that “chronic exposure to the weedkiller alters the gut microbiota functionality and composition interfering with carbon and fat metabolism, as well as homeostasis.”
The catalog of research surrounding the possible side effects of Roundup and glyphosate exposure is highly contentious. While scientific studies have sought to establish an indisputable link between exposure to Roundup and potentially life-threatening diseases, like cancer, in humans, the makers of Roundup remain steadfast in their claims that the weedkiller has no adverse effect on the health of humans or animals. According to Bayer, glyphosate poses no threat to animals because the chemical is designed to target an enzyme that is found only in plants and microorganisms. However, a growing body of evidence suggests that Roundup has a “proven indirect adverse effect on vertebrates and invertebrates via the gut microbiota,” which animals rely on for growth, pathogen defense and immunity.
“Our results show that chronic exposure to concentrations of Roundup and glyphosate at the approved regulatory threshold for drinking water causes embryonic development failure and alteration of key metabolic functions via direct effect on the host molecular processes and indirect effect on the gut microbiota,” the researchers concluded. “The impact of the weedkiller on [the keystone species Daphnia] has cascading effects on aquatic food webs, affecting their ability to deliver critical ecosystem services.”
More than 125,000 Roundup lawsuits have been brought against Bayer and Monsanto by consumers who allege that they developed cancer and other devastating side effects from exposure to toxins in the weedkiller. Each of the Roundup lawsuits involves similar allegations that the manufacturing companies failed to warn consumers about the health hazards associated with Roundup use, including the alleged increased risk of non-Hodgkin’s lymphoma and other cancers. A handful of early Roundup trials ended with substantial verdicts against the manufacturers, who have since moved towards resolving a large chunk of the remaining Roundup claims. In June 2020, Bayer announced that it would pay close to $11 billion to settle the bulk of the existing Roundup lawsuits, in addition to setting aside $1.25 billion for future lawsuits.