1,3 Butadiene, a Vapor Phase Component of Environmental Tobacco Smoke, Accelerates Arteriosclerotic Plaque Development

Abstract

Background Our recent results support predictions from epidemiology studies that thousands of excess heart disease–related deaths result yearly in the United States from involuntary exposure to environmental tobacco smoke (ETS). Limited exposures of cockerels to ETS significantly accelerate arteriosclerosis. Despite little direct in vivo support, tar fraction rather than vapor phase compounds are considered largely responsible for the plaque-promoting effects of cigarette smoke. Here, we evaluate the effects of two ETS components on plaque development: the vapor phase component, 1,3 butadiene, and the tar component, the tobacco-specific N -nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). At relatively high doses, injected NNK is carcinogenic in rodents. Epidemiology studies have identified increased mortality from arteriosclerotic heart disease among black men working in the butadiene rubber industry. Neither butadiene nor NNK has been tested experimentally for a possible role in plaque development. Methods and Results Cockerels inhaled butadiene (20 ppm; 16 weeks) or were injected biweekly with NNK (10 mg/kg, 16 weeks). Control cockerels were exposed to filtered air or were injected with the NNK solvent dimethylsulfoxide. Plaque incidence, prevalence, location, and size were determined double-blind. NNK had no significant effect on any of these measurements. In contrast, butadiene elicited a statistically significant increase in plaque size comparable to that seen after steady-state exposure to ETS from 5 cigarettes. Conclusions (1) This study represents the first time that a single cigarette smoke component has been demonstrated to accelerate arteriosclerosis, at a dose that is environmentally relevant. (2) The plaque-promoting components of ETS may reside in the vapor phase. (3) The cockerel model should be valuable in understanding the mechanism underlying the reported increases in heart disease deaths among black workers in the butadiene rubber industry.