Introduction

1. Carbon monoxide is a gas produced in the process of combustion, be it in a motor car engine, domestic heating, a cigarette or a forest fire. Of all the pollutant gases, it is one of the most dangerous since it can and does cause death. However, this fatal consequence is confined to people exposed to very high levels produced for example, by fires in buildings, blockage of flues, faulty appliances and deliberate self-poisoning by car exhaust gases. In the indoor environment individuals are exposed to carbon monoxide from sources such as domestic fuel burning heaters and gas cooking appliances. Outdoors, the main sources of carbon monoxide are vehicle exhausts, and the threat to health in such circumstances is a reduction in the oxygen-carrying capacity of the blood that may increase the risk of problems in individuals with ischaemic heart disease.
2. In this document, the Panel discuss the main sources of carbon monoxide in the general outdoor atmosphere, methods of measuring its concentration and the levels recorded in the United Kingdom, and its possible effects on health. We then recommend an Air Quality Standard for the United Kingdom for carbon monoxide.