Pesticides find their way into creeks, rivers and the oceans, threatening aquatic life and the safety of drinking water.

The most harmful pesticides commonly found in California are pyrethroids and organophosphates. Many organophosphates were taken off the market in 2005 due to their health impacts on birds and small children, targeting nerve signals with additional links to leukemia, but some are still in use. Pyrethroids, however, have limited restrictions, and while not as toxic to humans can cause extensive damage to fish and invertebrates. 

Research from the American Chemical Society shows that in 2016, 75 percent of dust collected in residential areas had traces of at least 5 different types of pesticides, of which 55 percent were pyrethroids. In much of the state, storm drains transport pesticides from garden and field runoff directly to surface waters.

The majority of pesticides are hydrophobic, meaning they repel water as much as possible and are theoretically easy to remove. Adsorption and distillation are appropriate treatment techniques. Adsorption uses charcoal filters with pores big enough for pesticides’ toxic components to become trapped to the surface. Distillation is a form of demineralization which requires boiling the water in question, catching its steam, then re-condensing it back to liquid form.