Lead arsenate compounds are used as insecticides in and around orchards. It persists in the soil many years after use and commonly is found in high concentration around filling places for spraying and dusting machinery and in old orchards from which trees have been removed.
"Lead Arsenate Toxicosis - A Case Report,"
Iowa State University Veterinarian: Vol. 32
, Article 1.
Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol32/iss1/1