Chapter 105 – Methyl Bromide

Publisher Summary This chapter briefly describes many of the published studies and elaborates the results from a number of contemporaneous unpublished methyl bromide toxicity studies by the oral and inhalation routes, which were conducted to support pesticide registration and other regulatory needs of the U.S. Environmental Protection Agency as well as state and international regulatory bodies. The primary focus is on methyl bromide-induced neurotoxicity. Methyl bromide is a broad-spectrum pesticide primarily used for soil fumigation, commodity/quarantine treatment, and structural fumigation. Fumigation typically occurs where the commodities are stored, such as in ship holds, grain elevators, warehouses, special fumigation chambers, and on shipping piers/docks. The toxicology of methyl bromide has been extensively reviewed. From a risk characterization standpoint, clinical observations of neurotoxicity are considered as the primary endpoint of concern from inhalation exposure. Reviewing the overall toxicity of methyl bromide shows that methyl bromide-induced toxicity is a function of both the concentration and the duration of exposure. Since human exposure is more likely to occur by the inhalation route, the majority of toxicologic evaluations for methyl bromide are inhalation studies. Ingestion of fumigated commodities is a secondary route of human exposure. People living in close proximity to fumigated fields, greenhouses, or structures are protected from the risk of significant inhalation exposure through special notice requirements, safety precautions, and the use of buffer zones. Neurotoxicity was the primary effect following inhalation exposures in acute and subchronic neurotoxicity studies in rats, in a series of specifically designed neurotoxicity studies in dogs, and in a developmental neurotoxicity study with direct inhalation exposure of dams and pups.