Use of Weed Killers Near a River

Written by joan norton
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Use of Weed Killers Near a River
Herbicide runoff contaminates waterways. (Darrin Klimek/Lifesize/Getty Images)

Pesticides include insect poisons and weed killers, and, according to the University of Wisconsin Extension website, they pose the same danger when used near rivers and other waterways. Pesticide labels recommend not using them near water, but pesticides and herbicides inevitably make their way into bodies of water via runoff from rain, sprinklers, irrigation systems, storm drains or agricultural drainage tiles.


In a study funded by the National Science Foundation, Rick Relyea of the University of Pittsburgh found that tadpole species biodiversity was reduced by 70 per cent in water containing Roundup weed killer. Roundup is the most frequently used weed killer worldwide.

Glyphosate is the main ingredient of Roundup, but it is the "inactive ingredients" that create a toxic effect on amphibians and humans. Roundup weed killer has also been identified by University of Caen, France researchers as a chemical compound that causes miscarriage and cell distortions(Ref.4).

Manufacturer's Recommendations

Monsanto, manufacturer of Roundup and Roundup genetically modified seed products, recommends that weed killer be kept out of water sources. According to the University of Pittsburg researchers, "While it may be intended for terrestrial use, there is overwhelming evidence that Roundup gets into aquatic habitats, typically through inadvertent (or unavoidable) aerial overspray." Many amphibian animals reproduce in small temporary wetlands next to rivers and lakes. These temporary wetlands are often subjected to aerial herbicide spraying.

Toxic Combinations

Glyphosate alone has been determined by the EPA to be non-toxic in rivers. Its label carries only a warning for possible eye irritation. Surfactants are chemicals added to herbicides to help them be absorbed by plants. POEA (polyethoxylated tallowamine, a chemical derived from animal fat) is Roundup's surfactant.The effect of the combination of POEA and glyphosate is highly toxic. A 98 per cent fatality of tadpoles was reported in waters containing the herbicide glyphosate.

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