PM2.5 and NO2 assessment in 21 European study centres of ECRHS II: annual means and seasonal differences

Abstract

The follow-up of cohorts of adults from more than 20 European centres of the former ECRHS I (1989–1992) investigates long-term effects of exposure to ambient air pollution on respiratory health, in particular asthma and change of pulmonary function. Since PM 2.5 is not routinely monitored in Europe, we measured PM 2.5 concentrations in 21 participating centres to estimate ‘background’ exposure in these cities. Winter (November–February), summer (May–August) and annual mean (all months) values of PM 2.5 were determined from measuring periods between June 2000 and November 2001. Sampling was conducted for 7 days per month for a year. Annual and winter mean concentrations of PM 2.5 vary substantially being lowest in Iceland and highest in centres in Northern Italy. Annual mean concentrations ranged from 3.7 to 44.9 μg m −3 , winter mean concentrations from 4.8 to 69.2 μg m −3 , and summer mean concentrations from 3.3 to 23.1 μg m −3 . Seasonal variability occurred but did not follow the same pattern across all centres. Therefore, ranking of centres varied from summer to winter. Simultaneously, NO 2 concentrations were measured using passive sampling tubes. Annual mean NO 2 concentrations range from 4.9 to 72.1 μg m −3 with similar seasonal variations across centres and constant ranking of centres between seasons. The correlation between annual NO 2 and PM 2.5 concentrations is fair (Spearman correlation coefficient r s =0.75), but when considered as monthly means the correlation is far less consistent and varies substantially between centres. The range of PM 2.5 mass concentrations obtained in ECRHS II is larger than in other current cohort studies on long-term effects of air pollution. This substantial variation in PM 2.5 exposure will improve statistical power in future multi-level health analyses and to some degree may compensate for the lack of information on within-city variability. Seasonal means may be used to indicate potential differences in the toxicity across the year. Across ECRHS cities annual NO 2 might serve as a surrogate for PM 2.5 , especially for past exposure assessment, when PM 2.5 is not available.