An epidemiological study of acute carbon monoxide poisoning in the West Midlands

Objectives - To describe the epidemiology of carbon monoxide (CO) poisoning in a defined population, identifying those at greatest risk from acute poisoning resulting in admission to hospital or death. Methods-A retrospective study with routinely collected information, set in the former West Midlands Regional Health Authority; population of 5.2 million. The data comprised 939 deaths and 701 hospital admissions due to CO poisoning between January 1988 to December 1994. The main outcome measures were age and sex standardised incidence rates (SIRs) for non-intentional, suicidal, and undetermined poisonings for health authorities and the linear relation with socioeconomic deprivation. Results-Overall rate of non-intentional poisonings over the 7 year period was 7.6/100 000, an annual rate of 1.1/100 000. The 7 year rates were highest in people greater than or equal to 85; men 24.0/100 000 and women 19.7/100 000. For suicides the 7 year rate was 19.6/100 000, an annual rate of 2.8/ 100 000. The 7 year rates were highest for men of 35-39, 64.1/100 000, and for women aged 45-49, 15.3/100 000. None of the causes of poisoning were related to deprivation. Non-intentional poisonings showed a strong seasonal variation with the highest rates being recorded in the months October to March. Increased rates of poisoning were found in the rural districts of the West Midlands. There seems to have been a decline in suicides coinciding with the introduction of three way catalytic converters on cars. Conclusions-Elderly people and the very young are at the greatest risk from non-intentional CO poisoning and rates are highest in the winter months. Although deaths from non-intentional CO poisoning are declining nationally, in the West Midlands they have remained stable and hospital admissions are increasing. It is not solely an urban phenomenon with rates for non-intentional CO poisoning and suicides higher in the rural districts. Health authorities need to consider all populations in any prevention programme. Further work is needed to establish the extent of the burden of chronic CO poisoning and the impact of catalytic converters on suicides.