A new study by scientists from the Helmholtz Centre for Environmental Research (UFZ) proves how the impact of pesticides are damaging waterways. While pesticides do protect crops from invasive species of insects, fungi, and weeds, they may do more harm than good. They inevitably runoff into nearby streams, damaging aquatic communities, which are essential to the food chain. Marine life helps maintain biodiversity and purify water as well.

The team of scientists found that government regulations generally are lax when it comes to pesticides. Even more alarming, 80% of waterways exceed these superfluously high pesticide levels. They published these findings in the scientific journal Water Research.

 In the study, they explain that biodiversity loss will continue unless pesticide use decreases dramatically. The scientists suggest that governments perform a thorough environmental risk assessment of pesticides.

For two years, the team studied pesticide contamination at over a hundred monitoring sites at waterways flowing through mostly agricultural land. These lowland regions were located in 12 federal states in Germany. Not surprisingly, they found that pesticide levels in most waterways drastically exceeded government standards.

The science showed that most waterways were impacted by pesticides on dangerously high levels.

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In a staggering 81% of small streams, the team found exceedingly high RAC values. These refer to the concentration of an active ingredient specified in the official regulations of pesticides. To prevent negative effects on aquatic communities, this level should never exceed the threshold. Sadly, in 18% of the waterways, over 10 pesticides surpassed the RAC recommendations.

“We have detected a significantly higher pesticide load in small water bodies than we originally expected,” says Prof. Matthias Liess, an ecotoxicologist at the UFZ and coordinator of the small water monitoring project.

Scientists found the following in some of the waterways tested:

  • The insecticide thiacloprid exceeded the RAC value by more than 100-fold
  • In 27 streams, the insecticides clothianidin, methiocarb, and fipronil exceeded the RAC value 10- to 100-fold
  • Herbicides such as terbuthylazine, nicosulfuron, and lenacil also surpassed the RAC value 10- to 100-fold

After analyzing the data collected, the researchers found that the impact of pesticides affect aquatic invertebrates more than previously thought. These species react to pesticides at much lower concentrations than prior pesticide risk assessments suggest. Of course, the sensitivity to pesticides depends on the species studied. For example, insects like caddisflies and dragonflies have much lower (1.000-fold) pesticide thresholds than snails and worms.

“For sensitive insect species, the pesticide concentration in the small lowland streams is the most relevant factor that determines their survival. In contrast, other environmental problems such as watercourse expansion, oxygen deficiency, and excessive nutrient content are less important. For the first time, this study allows a ranking of environmental problems,” says Liess.

The study found that current pesticide regulations grossly underestimate aquatic species’ sensitivity to the chemicals. Prior environmental risk assessments of pesticides only included data collected from laboratory findings, artificial ecosystems, and simulation models. However, according to Liess, real-world results differ vastly from the laboratory findings.

The research by the German scientists is the first to study the actual ecosystem rather than just a simulation. Now, there’s much more clarity on the harmful impact of pesticides on waterways and marine life.

Rainfall can make pesticide levels even higher in waterways.

“In addition to pesticides, many other stressors act on organisms in the ecosystem. These make them much more sensitive to pesticides. Natural stressors such as predation pressure or competition between species are not sufficiently considered in the risk assessment. But these obvious problems often go unnoticed because the degree of pesticide contamination and the effect of this have not been validated in the field — neither in Germany nor in other countries,” he says.

Throughout the project, the team discovered that pesticide levels differed depending on the type of samples taken. They took two types of samples: scoop and event samples. Scoop refers to a random sampling of water specified by the EU Water Framework Directive. In an event sample, an automatically controlled sampler takes water samples from the waterway following rainfall.

“The event sample provides much more realistic results because the pesticides enter the water bodies as a result of the increased surface run-off from the field, especially during rain,” says Liess. Researchers found that pesticides measured 10 times higher after rainfall compared with scoop samples.

Matthias Liess says this:

“In order to realistically depict the water pollution, samples must therefore be taken after rainfall events. That’s why we need an official regular environmental monitoring to be able to assess the amount and the effects of pesticides.”

He and his team demand that governments incorporate these findings into new pesticide approvals immediately.

“We are still using pesticides that were approved many years ago based on an outdated risk assessment. This must therefore change as soon as possible. Only in this way can we preserve the biodiversity in our waters and with it the services that these biotic communities provide for our ecosystems.”

This study only included the impact of pesticides on waterways in Germany. However, in the US, many waterways have also been contaminated by the impact of pesticides. A new study published in March 2021 by the American Chemical Society found that 90% of streams sampled contained extremely toxic pesticide breakdown products.

“The pesticide industry has conditioned Americans to believe the fiction that these highly toxic pesticides just magically vanish,” said Jess Tyler, a scientist at the Center for Biological Diversity. “This study should be a wake-up call to the pesticide regulators at the Environmental Protection Agency and the Biden administration, that they can’t keep ignoring the well-documented, systemic pesticide pollution of our landscapes and waterways.”

Final thoughts on a study showing how pesticides impact waterways and the water supply

Pesticides allow for higher crop yields since they protect agricultural products from insects and fungi. However, they also have a dark side: they cause lasting, widespread degradation to waterways and animals. A new German study revealed that over 80% of waterways contained dangerously high pesticide levels. After rainfall, pesticide levels increased, even more, up to ten times higher in some cases.

Waterways in the US also contain exceedingly high pesticide levels. The US produces more food than any country in the world, so pesticides are a necessary evil. However, it’s clear that pesticides cause damage to our waterways and animal life. Are the consequences worth it? That’s a difficult question to answer, but the health of our planet hangs in the balance.