Monitoring nitrogen dioxide and its effects on asthmatic patients: two different strategies compared

Objectives: To develop a 'methodology assessment' to evaluate the strengths and the weaknesses of two different epidemiological approaches and to identify the best suited monitoring strategy to measure the effects of 'normal levels' of nitrogen dioxide exposure on the health of an urban population. Methodology: all exposures to nitrogen dioxide were determined with passive samplers, each sampler consisting of 3 measuring Palmes tubes. In the first study the nitrogen dioxide exposure was assessed in 23 school children (11 asthmatic and 12 non asthmatic). Children wore samplers for a week and parallel measurements were made in their kitchens, in bedrooms and outside their homes. The second study consisted in a case-control study where the relative risk of hospital admission was calculated considering nitrogen dioxide levels in a city of northern Italy. 110 asthmatic patients were compared to a control group of 5322 people. Results: Personal sampler measurements highlighted significant differences in exposure when nitrogen dioxide atmospheric levels were compared in asthmatic and healthy children (p<0.05). No other parameters were significant in the two groups. A significant action of atmospheric nitrogen dioxide on hospital admission was demonstrated (p<0.01). Conclusions: Although a cause-effect relation as such cannot be identified, the studies show a relation between the exposure to nitrogen dioxide and the presence of adverse effects on people's health. However the 'disadvantage' is for subjects with asthmatic pathologies, compared to the others. To manage this problem most effectively, a combined approach with the activation of specific personal monitoring campaigns of the subjects with verified risk seems necessary. This requires 'reading' the data resulting from most extensive and up to date information systems, capable of a thorough control both of the living environment and of the clinical outcome of the whole population.