The Effect of Catalytic Converter Legislation on Suicide Rates in Grampian and Scotland 1980–2003

Abstract

Objective To examine the effect of catalytic converter legislation on suicide rates in Grampian and Scotland since its implementation in 1993. Methods 1. Population study in Grampian and Scotland using national population and mortality statistics for 1980 to 2003. 2. Retrospective, controlled cohort study of individuals who had unsuccessfully attempted suicide by motor vehicle exhaust gassing to examine the theory of method substitution. Results There was a significant fall in suicides by motor vehicle exhaust gas inhalation in Scotland and Grampian following the introduction of compulsory catalytic converter legislation. However, in the same time period, there was a significant increase in numbers of suicides by hanging and total suicide rates in Scotland. There was a non-significant trend in a small sample of patients from a local hyperbaric unit for an increased rate of subsequent completed suicide between those who had previously attempted suicide by motor vehicle exhaust gas inhalation and controls. Conclusions Catalytic converter legislation has resulted in a decrease in the number of suicides by motor vehicle exhaust gas inhalation. Overall suicide rates have not decreased. There is evidence to suggest that those who would have previously committed suicide by motor vehicle exhaust gas inhalation find alternative methods of suicide, so called ‘method substitution’. Initiatives to reduce suicide rates should be directed at those means that are used by impulsive suicide attempters, as other, determined individuals, will commit suicide by another method.