As part of the National Surface Water Quality Monitoring Programme ('NAWA spez 2023'), the Swiss Federal Institute of Aquatic Science and Technology (Eawag), together with partner institutions, systematically investigated how pesticides make their way into surface waters. The result, published in early October 2025, is surprising: only part of the contamination can be traced back to diffuse runoff from crop production.

Many substances—particularly insecticides—originate from sources much closer to our everyday lives. Active ingredients such as imidacloprid or fipronil, which have long been banned as plant protection products, still reach rivers and streams via wastewater treatment plants. They come, for example, from flea and tick treatments for pets, from cleaning and disinfecting agents, or from wood preservatives. Residues can cling to animal fur, hands or textiles and wash off into sewage systems, eventually ending up in waterways. This shifts the focus—from the field to the laundry room. Laundry room? We’ve heard that before—right, glyphosate! A study showed that glyphosate can also form as a degradation product of certain detergents. Again, it’s clear that pointing fingers solely at crop protection products misses the full picture.

The new NAWA analysis highlights that everyone’s daily habits play a role. Pet owners who use certain insect repellents, for instance, may inadvertently contribute to water pollution. Likewise, cleaning products, biocidal sprays, or treated materials can add to the overall chemical load. Part of the problem, it seems, lies literally within our own four walls.

From an ecotoxicological perspective, insecticides remain the main risk drivers for aquatic organisms. In the study, concentration limits were exceeded particularly for cypermethrin, imidacloprid, metazachlor, metribuzin, nicosulfuron, and thiacloprid. Many of these substances are now banned as plant protection products but continue to circulate as biocides or veterinary medicines. Even after regulatory action, these compounds persist in the environment.

A Broader Focus Is Needed

Pathways of entry differ significantly by substance. Diffuse runoff is typical for current crop protection products such as aclonifen, which are washed off fields during rain. Entry via wastewater treatment plants, on the other hand, is characteristic of substances from non-agricultural uses, such as imidacloprid or fipronil. Many substances follow both pathways in parallel, depending on location and use. The responsibility is therefore widely shared. Not only farms but also households, veterinarians, small businesses, and consumers contribute to the chemical burden on surface waters.

The study makes one thing clear: pesticide contamination is not solely an agricultural problem. The pathways are diverse—and some lead directly from our bathrooms and laundry rooms into the streams. Protecting our waters therefore begins not only in the fields, but also at home.