Personal exposures of children to nitrogen dioxide relative to concentrations in outdoor air

To investigate the relation between fluctuations in personal exposure to nitrogen dioxide (NO(2)) in school children and changes in outdoor NO(2) concentrations.

114 Asthmatic school children aged 7-12 years were recruited from the Southampton area. Weekly average personal exposures to NO(2) were measured over a 13 month period with passive diffusion tubes. At the same time, outdoor NO(2) concentrations were monitored at a fixed site in the centre of Southampton. Correlations between weekly personal exposures and mean outdoor concentrations during the same periods were examined.

Mean duration of follow up was 32 weeks. Measurements of weekly mean personal NO(2) exposures were generally low and ranged from 2.47 to 1751 [corrected] micrograms/m(3) with a geometric mean of 60 [corrected] micrograms/m(3). Substantial variation in personal exposures occurred between children and more especially within individual children from week to week. Daily outdoor concentrations of NO(2) ranged from 15.2 to 105.2 [corrected] micrograms/m(3), with a geometric mean of 43.4 [corrected] micrograms/m(3). There was no evidence of seasonal variation in outdoor concentrations. No significant correlation was found between each child's weekly mean personal exposures to NO(2) and mean outdoor concentrations for the corresponding periods.

At low outdoor NO(2) concentrations, fluctuations in NO(2) in outdoor air as measured at a central monitoring station do not contribute importantly to variations in personal exposure when averaged over a week.