23
Jun
Pesticide Contamination in Waterways Raises New Alarm for Aquatic Life, Citing Poor Regulation
(Beyond Pesticides, June 23, 2021) Small streams are prone to excessively high levels of pesticide contamination that are even more hazardous than once thought, according to a pilot study generated by a team of German researchers. The results indicate significant risks for the health of aquatic ecosystems and should be used as evidence for establishing greater protections from toxic pesticide use, researchers say. With many aquatic benchmarks set by the U.S. Environmental Protection Agency lower than those established in Germany and the European Union, and evidence of widespread pesticide contamination in America’s waterways, the study could have even greater weight for for U.S. regulatory agencies’ deficiencies.
Scientists established monitoring sites at more than 100 streams throughout Germany over the course of two years. Most sites were established near farm fields, where chemical farmers will use highly toxic pesticides than often make their way into local waterways. Streams were monitored for pesticide concentrations, with particular eye to whether they met the country’s regulatory acceptable concentration (RAC value) in a given water body. The RAC value is intended to be the highest level at which there will be no adverse effects on aquatic life, however these regulatory levels often do not correspond with real world conditions.
The results are significantly worse than researchers anticipated. “We have detected a significantly higher pesticide load in small water bodies than we originally expected,” said Matthias Liess, PhD ecotoxicologist and coordinator of the water monitoring project. RAC values are exceeded in 81% of streams tested. For nearly 1 in 5 streams, RAC values are exceeded for over 10 different pesticide compounds. Certain pesticides are astronomically higher than their RAC value. The neonicotinoid thiacloprid is found in three streams at 100x higher than its RAC value. Twenty-seven streams exceed RAC value between 10 and 100x for the following pesticides: clothianidin, methiocarb, and fipronil, terbuthylazine, nicosulfuron, and lenacil.
Moreover, the data collected allowed scientists to further determine whether RAC values themselves are adequately protective. For the most sensitive aquatic species, such as caddisflies and dragonflies, researchers say that these species require 1,000x lower threshold values than less sensitive animals like 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,” said Dr. Liess.
Dr. Liess indicates that the results show that the current process for evaluating sensitive aquatic species – using laboratory studies, artificial ecosystems, and simulations, do not adequately account for real world stressors. “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 taken into account 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 notes.
Scientists say that testing protocols may also be missing the mark. Testing conducted after a rain event, rather than regular testing at any given time, resulted in detections of pesticides 10x higher than regular testing. “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”, Dr Liess said. “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.”
Dr. Liess indicates that his team’s findings should immediately be incorporated into the process that regulatory agency’s use to determine pesticide safety. “We are still using pesticides that were approved many years ago based on an outdated risk assessment,” he said. “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.”
While streams in Germany may be worse than researchers expected, U.S. streams are likely more contaminated due to higher RAC values (called aquatic benchmarks by EPA) with less regulatory oversight and testing. The data that is available from the U.S. Geological Survey shows that nearly 90% of water samples in US rivers and streams contain at least five or more different pesticides.
To stem the tide of pesticide contamination in waterways, embrace a farming system that eschews the use of toxic chemical pesticides by purchasing organic whenever possible. Any pesticide approved for organic use undergoes and independent assessment by a board of experts, and must meet higher standards of safety for human health and ecological systems. Read here why organic is the right choice, and see Beyond Pesticides Contaminated Waters webpage for more information on the dangers these chemicals pose to American waterways.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: EurekAlert! press release
