Spatial variations in the concentrations of traffic-related pollutants in indoor and outdoor air in Huddersfield, England

As part of the Small Area Variations in Air Quality and Health (SAVIAH-2) study, monitoring was carried out for a number of traffic related pollutants (mass and absorbance of PM10 and PM2.5, benzene, B(a)P and PAHs) indoors and outdoors of homes in an area of Huddersfield, England. Homes were selected on the basis of their distance from nearby major roads. Monitoring was conducted during two 2-week periods. On each occasion, pollution levels were measured in paired ‘proximity’ (within 50 m of the main road) and ‘background’ (>50 m from the main road) homes, for a 24 h period, using active pump samplers. Spatial variations in pollutant concentrations were modest and in most cases did not show significant associations either with distance from road or modelled NO2 concentrations. Neither of these commonly used measures would thus seem to provide reliable indicators for these traffic-related pollutants in this study area. Several of the measured pollutants showed significant inter-correlations, but overall absorbance of the fine particulate fraction displayed the strongest correlations, and would appear to provide the best general marker for these pollutants, perhaps reflecting the importance of diesel vehicles as a major emission source. Indoor–outdoor ratios of PM10, PM2.5 and absorbance of these fractions were below 1, but other pollutants did not show significant differences between indoor and outdoor concentrations. However, all the pollutants showed significant positive correlations between indoor and outdoor concentrations, strongest correlations being seen for the absorbance measures of the particulate fraction. This suggests that outdoor concentrations may give a useful measure of exposures to traffic-related pollutants for use in epidemiological studies.