Leaded Pesticides

Legacy leaded pesticides that were commonly used in agricultural areas present another source of lead exposure to humans and animals. Lead arsenate was the most widely used arsenic based pesticide to control the gypsy moth around the late 1800’s in the U.S. The successful application of lead arsenate against the gypsy moth, and the easy manufacturing process that allowed farmers to prepare it at home, resulted in widespread use of lead pesticides across the U.S.

Largely used on fruit crops, this pesticide began to be phased out of use once it was realized that washing the fruit vigorously did not remove lead residues. It was eventually abandoned when DDT became available in 1948. Lead arsenate can persist in the environment for a very long period of time. Studies conducted as late as 1998 showed high concentrations of lead remaining in soil where this pesticide was previously applied.

There is a strong correlation between the use of lead pesticides and lead poisoning of raptors, such as golden eagles, bald eagles and hawks, because of the fact that lead pesticides were once very prevalent in agricultural use, especially on orchards in Washington. (Department of Washington Fish and Wildlife Report, Feb. 12, 2001) Due to its high solubility, lead arsenate can leach into the ground, groundwater and surface waters (Columbia River) and migrate to soils downstream. Thus, ground squirrels living in burrows in and around orchards are very likely to be exposed to lead in the soil. Because ground squirrels have been shown to be a major diet item of hawks and golden eagles, this situation provides a plausible exposure pathway due to lead in the soil.

Lead pesticides illustrate yet another abundant source of highly soluble compounded lead in the environment and a potential for lead exposure to humans and wildlife.