Butadiene inhalation accelerates arteriosclerotic plaque development in cockerels

1,3-Butadiene (BD), a gas widely used in the rubber industry, is also present in automotive exhaust and in the vapor phase of environmental tobacco smoke (ETS; approximately 400 micrograms/cigarette). The threshold limit value (TLV) for BD which was 10 ppm, has now been reduced to 2 ppm. Extensive investigations of workers have identified very few statistically significant increases in BD-associated cancer mortality. However, two studies have reported increased BD-associated mortality from arteriosclerotic heart disease in black workers in the BD rubber industry. The cockerel is a sensitive animal model for studying effects of environmental agents on arteriosclerosis development. Previous studies showed that inhaled environmental levels of ETS significantly accelerate arteriosclerosis. Surprisingly, the carcinogen-rich tar fraction of ETS was ineffective. The elevated risk of death from arteriosclerotic heart disease in black BD workers and the high BD level in the vapor phase of ETS, raised the question of whether BD would accelerate arteriosclerosis in cockerels. Here, cockerels breathed either 20 ppm BD or filtered air (6 h/day, 80 days). Blinded measurements showed no differences between groups in plaque frequency or location. However, plaque sizes were significantly larger in BD-treated cockerels than in controls--results nearly identical to those reported earlier for ETS-exposed vs. air-exposed cockerels. This indicates that BD may contribute to the atherogenicity of ETS and provides experimental support for the recent reduction in the TLV for BD.