Personal PM10 exposure in asthmatic adults in Padova, Italy: seasonal variability and factors affecting individual concentrations of particulate matter

Personal exposure to PM10 measured in different seasons in a sample of asthmatic subjects living in Padova (Northern Italy) was compared with simultaneously measured outdoor PM10 concentrations. The specific contribution of ambient PM10 and other factors to individual exposure was evaluated in one of the areas of Europe with the worst air pollution.Thirty-one asthmatic subjects (21 non-smokers and 10 smokers) carried personal PM10 monitors for six 24-hr sessions, in different seasons of the year. Concomitant daily 24-hr ambient PM10 concentrations were measured by air quality monitoring networks. A multivariate analysis was performed to identify factors explaining personal exposure to PM10, using a random effect model.The analysis on the 31 subjects referred to a total of 155 observations. The mean personal PM10 exposure was higher (range 79.3–126.1 μg/m3) than the outdoor concentrations (range 37.3–85.4 μg/m3) in all seasons; and personal exposures varied less than outdoor PM10 levels from one season to another. Smokers had significantly higher personal PM10 concentrations than non-smokers (127.99 vs 78.8 μg/m3; T=−5.70; p<0.001). Moderate correlations emerged between outdoor and personal PM10 concentrations. The correlation improved after excluding subjects exposed to active or passive smoking (median Pearson's R 0.41 vs 0.26). Considering all the subjects, smoking was the main factor affecting personal exposure, contributing to 41% of the variability. Outdoor PM10 concentrations (25%), temperature (12%) and season (15%) also contributed to personal PM10 exposure. Outdoor PM10 (46%), temperature (20%), season (19%) and time spent indoors (6%) were significantly associated with personal exposure in non-smokers.We concluded that it is crucial to perform personal monitoring and to evaluate the complexity of factors that contribute to individual PM exposure. While tobacco smoke was the primary source of PM10 in all subjects, the contribution of ambient components was particularly relevant for the personal exposure levels of our non-smokers living in a highly-polluted environment.