Personal exposure to benzene and the influence of attached and integral garages.

Benzene is an air pollutant that is a recognised human carcinogen. An air quality standard has been established for ambient air in the UK to reduce the population's exposure. It has been estimated that about 70% of benzene emissions to air in the UK come from petrol vehicles. A number of studies, including the Avon Longitudinal Study of Pregnancy and Childhood in the UK, have found that benzene concentrations in homes with attached or integral garages tend to be higher than in those without such garages. The present paper reviews these studies and reports a detailed investigation of five homes with either an attached or an integral garage. Indoor and outdoor locations were monitored using diffusive sampling to determine the average benzene concentration over approximately 28 days each month for 18 consecutive months (June 1998-November 1999). For one of these homes, ten years of data had shown the indoor benzene concentration to be consistently higher than outdoors. Personal exposure monitoring of one adult in this home showed that the benzene concentration in the main bedroom was a better predictor of personal exposure than the concentration outdoors. In the homes where a car was regularly parked in the garage, 18-month average benzene concentrations of up to 101.3 micrograms m-3 were measured in the garage, which is more than six times the ambient air quality standard for benzene (16.25 micrograms m-3 running annual average). Mean benzene values in all cars and most of the garages studied exceeded the benzene standard. Mean benzene concentrations in the room above the garage ranged from 3.7 micrograms m-3 in one home, where the car was rarely parked in the garage, to 39.9 micrograms m-3 in another home where a car with high benzene emissions was parked in the garage for six of the 18 months monitored. The mean benzene concentration in the room above the garage in this latter home was nearly 2.5 times the ambient air standard. The study demonstrates that there is a potential for people to have a higher exposure to benzene as a result of living in a home with an attached or integral garage. An understanding of routes of personal exposure is important to develop effective policies to reduce risks to health.