Great concern arises when pesticides are consumed by animals, remain intact, and work their way up the food chain. Pesticides that have this trait have been removed from the US market. However, scientists lacked the means to determine effects of very long term exposures to low concentrations of these chemicals in the body. While there is potential for an undesirable level of exposure if a treated site is entered before the spray dries, research with lawn chemicals has shown that the amounts picked up on clothing, feet, hands, etc., once the spray has dried are well within safe limits. The soil and the thatch in turf are key sites for processes that immobilize or break down pesticides.
Adsorption occurs rapidly, such that strongly adsorbed chemicals essentially have no soil activity.
Thus pesticides that are strongly adsorbed are not available for root uptake and have a low leaching potential. However, adsorbed chemicals still can move off-site by soil erosion. Once chemicals are adsorbed, they may be broken down by soil organisms. Soil microbes are the most important actors in the fate of pesticides since microbial degradation is the ultimate fate of most pesticides. Rates are described in terms of half-lives which may be days, weeks, or months depending on the chemical.