BRONCHIAL RESPONSIVENESS, EOSINOPHILIA, AND SHORT-TERM EXPOSURE TO AIR-POLLUTION

The number of capillary blood eosinophils and the prevalence of bronch ial hyperresponsiveness (BHR) were compared between schoolchildren liv ing in a polluted area (Ardal) and unpolluted area (Laerdal). In Ardal there is an aluminium smelter emitting sulphur dioxide and fluoride t o the environment. Daily measurements of these pollutants in ambient a ir were available. The mean number of eosinophils in Ardal was 220 x 1 0(6)/l compared with 106 x 10(6)/l in Laerdal. The prevalence of BHR w as 15.9% in Ardal and 11.8% in Laerdal. The odds ratio of having BHR i n relation to these pollutants during the last 24 hours were: 1.12 (95 % confidence interval (CI) 1.01 to 1.24) by increasing sulphur dioxide with 10 mu g/m(3), and 1.31 (95% CI 1.07 to 1.60) when fluoride expos ure increased with 1 mu g/m(3). Similarly, these exposures were associ ated with a decrease in eosinophils of -21 x 10(6)/l (95% CI -36 to -6 ) and -52 x 10(6)/l (95% CI -98 to -8), respectively, in atopics. It i s hypothesised that recent exposure to irritants induces changes in th e airways leading to BHR in addition to recruitment of eosinophils to the airways in atopic subjects.