Many toxic pesticides have been banned by the EU, however some can remain in the environment for many decades. Aquatic invertebrates are particularly vulnerable to pesticides, which can alter their feeding behaviour, growth and mobility. New research has found that persistent pesticides can increase toxicity in streams by up to 10 000 times compared to the residues of currently used pesticides. The researchers recommend these be taken into account when calculating overall toxicity.
- Findings comprised a range of contemporary and banned legacy pesticides in streams.
- Groundwater is a significant pathway for some herbicides entering streams.
- Legacy pesticides increased predicted aquatic toxicity by four orders of magnitude.
- Sediment-bound insecticides were identified as the primary source for ecotoxicity.
- Stream monitoring programs should include legacy pesticides to assess impacts.
Banned pesticides continue to affect toxicity in streams, Science for Environment Policy, 12 January 2017.
Sources, occurrence and predicted aquatic impact of legacy and contemporary pesticides in streams, science direct, February 2015.
We couple current findings of pesticides in surface and groundwater to the history of pesticide usage, focusing on the potential contribution of legacy pesticides to the predicted ecotoxicological impact on benthic macroinvertebrates in headwater streams. Results suggest that groundwater, in addition to precipitation and surface runoff, is an important source of pesticides (particularly legacy herbicides) entering surface water. In addition to current-use active ingredients, legacy pesticides, metabolites and impurities are important for explaining the estimated total toxicity attributable to pesticides. Sediment-bound insecticides were identified as the primary source for predicted ecotoxicity. Our results support recent studies indicating that highly sorbing chemicals contribute and even drive impacts on aquatic ecosystems. They further indicate that groundwater contaminated by legacy and contemporary pesticides may impact adjoining streams. Stream observations of soluble and sediment-bound pesticides are valuable for understanding the long-term fate of pesticides in aquifers, and should be included in stream monitoring programs.