Pesticides in Stormwater FAQs
Pesticides are man-made substances used to control unwanted pests or vegetation. Pesticides are usually made up of a combination of active and inert chemicals and materials that can break down in the environment into substances often more toxic than the original materials. Examples of pesticides include insecticides, herbicides, fungicides, defoliants and desiccants.
Pesticides get into stormwater by being dissolved or attached to soil particles and carried away in runoff. Pesticides can also enter the groundwater if the pesticide is highly water soluble and applied before a large rainfall event or regular irrigation. A form commonly found in stormwater is 2,4- Dichlorophenoxyacetic acid (2,4-D); glyphosate (Roundup). [ii] DDT was in common use to control mosquitos in the United States until its residue was found to have serious effects on wildlife, especially birds and fish.
Pesticides should be removed from stormwater discharge because their presence in water sources can have serious, adverse effects on human health and the viability of fish and wildlife. Certain pesticides can irritate human tissue, damage the nervous, immune and endocrine (hormone) systems, increase the risk of cancer and even cause death.[iii]
Pesticides most frequently found in water at concentrations that are toxic to aquatic plants and invertebrates are not toxic to fish.[iv] However, the pesticides chlorpyrifos, diazinon, and malathion interfere with salmonids’ ability to swim, find food, reproduce, and escape predators.[v] Studies have also linked high pesticide levels with hormone imbalances in fish.[vi] DDT causes acute and chronic health problems for birds, including thin-shelled eggs and reproduction difficulties.[vii]
Enhanced, passive media filtration and advanced polishing can be used to effectively remove pesticides from stormwater prior to discharge. If further reduction is necessary to remove pesticides, advanced polishing technologies can be used. Both types of BMPs combined in a treatment train will remove pesticides from stormwater prior to discharge to help facilities meet benchmarks or NALs. The Aquip passive media filter and the Purus polisher in combination offer an advanced level of pesticide removal from stormwater. Learn more about our stormwater media filtration and polishing technologies.