Mutagenicity, carcinogenicity and reproductive effects of dibromochloropropane (DBCP)

Dibromochloropropane (DBCP), a brominated organochlorine nematocide, has been used since the mid-1950s. Its primary value was its effectiveness on perennial crops without damaging the plants. DBCP also had less acute toxicity than earlier soil fumigants such as ethylene dibromide. DBCP became widely used on citrus, grapes, peaches, pineapple, soybeans and tomatoes. In Central America and Israel, banana trees were treated with DBCP. By 1975, 25 million pounds were being produced in the U.S. per year. The majority of U.S. production was applied in the Pacific Coast states, particularly California's San Joaquin Valley, and the Southern Atlantic Coast states. Animal studies in the early 1960s revealed hepatic and renal effects and testicular atrophy in DBCP-treated rates. Testicular atrophy was noted at the lowest exposure level tested (5 ppm). In 1973, DBCP was found to cause gastric carcinoma in mice and rats, and mammary adenocarcinoma in rats. A later study linked DBCP to nasal cavity tumors in rats. DBCP is an in vitro mutagen after activation with microsomal enzymes. A dominant lethal effect has been observed in rats. DBCP also induces increases in sister-chromatid exchanges and chromosomal aberrations. Mean fetal weight and maternal weight gain is decreased in pregnant rats exposed to DBCP. In mid-1977, employees in a California pesticide formulation plant were discovered to be infertile. Further investigations documented azoospermia and oligospermia among many of the workers handling DBCP. These findings were duplicated in other DBCP production plants. In the United States, the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA) rapidly restricted the use of DBCP. The application of DBCP to all but pineapples in Hawaii was banned by the EPA in 1979. In 1982, the EPA exempted the peach crop in the Southern Atlantic coast states from the ban on DBCP use. Prior to the 1977 events, no such agent in workplace concentrations had been shown to produce infertility and sterility in otherwise healthy men. Subsequently, the interest in DBCP had led to many other studies, and has contributed to a heightened awareness about workplace hazards to both the male and female reproductive systems. This article will review the current state of knowledge of the in vitro, animal, and human toxicology of DBCP.