Toxicity of car exhausts and opportunity for suicide: comparison between Britain and the United States.

The rate of car exhaust suicides in the United States has declined following the introduction of emission controls in the mid-1960s, though not as much as the decline in CO emitted by cars. In Britain, where emission controls have not been introduced, the rate of these suicides, initially much lower than in the United States, has greatly increased since the beginning of the 1970s and is now about double that of the United States. This rise cannot be explained simply on the basis of an increase in the opportunities for suicide as represented by an increase in the number of cars but may be due to increased knowledge of the method. While these results are interpreted as generally supporting the potential for opportunity-reducing preventive measures, they also demonstrate that much more research is needed into the complex nature of the opportunity structure for suicide.