Sources of Exposure to 1,3-Butadiene

4. The 1,3-butadiene in the air derives solely from human activity. It is an important industrial chemical, being used particularly in the manufacture of synthetic rubber for tyres. Some commercial liquid petroleum gases also contain up to 8 percent by volume. However, apart from accidental releases from such industrial activities, the 1,3-butadiene in the ambient air comes from combustion. It is mainly derived from combustion of petrol and diesel fuel, but some also comes from house fires and the burning of other fossil fuels. 1,3Butadiene is also present in cigarette smoke.
5. There is little or no preformed 1,3-butadiene in diesel or in petrol, either leaded or unleaded; the emissions in the exhaust gases being produced by the combustion process itself. The chemicals in petrol from which the 1,3-butadiene is derived, higher olefins, have been present in increasing proportion in petrol over the last decade, and it is likely that the amounts of 1,3-butadiene released into the atmosphere have therefore been rising. However, 1,3-butadiene is removed efficiently by catalytic converters on motor cars and this is likely to reverse any such trend, while increasing use of diesel as a vehicle fuel would be expected partly to counter this.