Parathion may be stored in fat. Some fat storage of parathion does occur. However, upon release from fat storage, parathion is rapidly broken down and eliminated. Bioconcentration of parathion is low to moderate. It binds tightly to soil particles and is degraded by biological and chemical processes within several weeks.
Degradation is faster in flooded soil.
Residues of parathion can persist for many years, but usually remain in the upper 6 inches of soil. Sunlight can convert parathion into the active metabolite paraoxon, which is more toxic than parathion. In open water, parathion will usually disappear within a week, mainly by adsorption to suspended particles and bottom sediments. Adsorbed parathion is subject to degradation by microorganisms and chemical hydrolysis. In orange groves, the half-life of parathion is as long as one month.