Long-range transport of chlorpyrifos may be caused by spray drift, volatilization, or particle transport. Chlorpyrifos has been shown to form chlorpyrifos-oxon via indirect and direct photolysis. Although chlorpyrifos-oxon may be slightly more persistent in air (i.e., longer indirect photolysis half-life), chlorpyrifos-oxon is susceptible to indirect and direct photolysis.
The primary exposure pathway of chlorpyrifos-oxon to non-target organism in the environment is thought to be a result of photolysis of chlorpyrifos in air following volatilization. The available air monitoring data indicate that, when detected, chlorpyrifos-oxon may be found at levels that are on the same order of magnitude as the parent. Additionally, the available toxicity data suggest that chlorpyrifos-oxon is of similar toxicity for most taxa when compared to the parent and is perhaps more toxic to some taxa (especially aquatic-phase amphibians) and less toxic to other (e.g., aquatic invertebrates). Therefore, in general, the effects of chlorpyrifos-oxon to exposed non-target organisms are likely to be similar to those of chlorpyrifos.