Both laboratory studies and extensive field studies have shown that chlorpyrifos breaks down quickly in water. In laboratory studies, chlorpyrifos was added to pure water with a neutral pH factor. As with soil, chlorpyrifos’ half-life was about a month — with water and light (photolysis) contributing to its detoxification and breakdown. And, as with soil, more alkaline conditions resulted in faster breakdown — half-life was around two weeks.

In field studies, where samples of natural water from streams and canals were analyzed, chlorpyrifos often broke down significantly faster than in the laboratory — as much as 16 times faster. In fact, half-lives in the water of less than one day are typical, due to a combination of breakdown by microbes and plants, evaporation, and bonding with organic matter and sediments.

Further Resources

Racke, K.D. “Environmental Fate of Chlorpyrifos.” Reviews of Environmental Contamination and Toxicology, 1993, Volume 131:1-154.
http://www.ncbi.nlm.nih.gov/pubmed/7678349

Giddings, J.M. et al. “Fate of chlorpyrifos in outdoor pond microcosms and effects on growth and survival of bluegill sunfish.” Environmental Toxicology and Chemistry, 1997, Volume 16(11): 2353–2362.
http://onlinelibrary.wiley.com/doi/10.1002/etc.5620161122/abstract