Determination of acute toxic effects in mice following exposure to methyl bromide

Abstract

An inhalation system was designed and constructed for acute nose exposure of mice to methyl bromide. Animals were exposed for 1 h to concentrations ranging from 0.87 to 5.93 mg/l. Mice exposed to concentrations up to 1.72 mg/l did not exhibit any indication of developing a toxic response. Animals exposed to concentrations fo 2.20 and 2.70 mg/l exhibited significantly decreased lung and liver weights when compared to controls. Animals exposed to concentrations above 3.50 mg/l exhibited kidney lesions. At concentrations of 3.82 mg/l and above, animals exhibited abnormal clinical signs, weight loss, and mortality. In addition, at 4.70 mg/l, a liver lesion was observed. At concentrations above 5.77 mg/l, pathological changes were observed in the color and a decreased motor coordination was evident. Methyl bromide exposures of up to 3.82 mg/l did not affect the ability of mice to recall a single‐task passive‐avoidance test. The 1‐h LC50 of methyl bromide in mice via inhalation was determined to be 4.68 mg/l (approximately 1200 ppm). The dose‐response curve was quite steep and the LC10 to LC90 range of mortality was contained within a doubling of concentration.