The assessment of the effects of motor-vehicle exhaust gas on the respiratory symptoms of children, through a large-scale long-term longitudinal survey

从1973年到2003年，每隔2年或3年，对大坂府所有公立小学儿童进行了15次主观症状问卷调查。自1983年以来，儿童“咳嗽”的流行率一直保持在同一水平，约为10%。咳嗽患病率（10月调查）与当年7、8月平均气温呈显著负相关。据推测，夏季气候对“咳嗽”的患病率有影响。在对部分抽样学校的个体问卷数据进行logistic回归分析时，每次调查的“交通沿着道路沿线居民”与“咳嗽”的比值比为1.37 ± 1.70（p<0.001）。此外，“咳嗽”的患病率与“交通沿着居民”的百分比之间也存在显著相关性。由于“交通繁忙道路沿着居民”的比例与大气中二氧化氮（NO_2）浓度之间存在很强的相关性，因此认为该比例可作为机动车尾气污染的指标。1995年以来，大坂府“交通繁忙道路沿着居民”比例和NO_2水平略有下降。提示儿童“咳嗽”患病率下降是由于NO_2水平下降所致。此外，还估算了影响儿童咳嗽症状的NO_2浓度的年平均下限为0.022 ~ 0.024ppm。

A total of 15 questionnaire surveys on subjective symptoms have been conducted on all public elementary-school children in Osaka Prefecture at 2- or 3-year intervals between 1973 and 2003. The prevalence rate of "coughing" among children has remained at the same level, approximately 10%, since 1983. A significant inverse correlation was observed between the prevalence rate of "coughing"(surveyed in October) and the mean temperature in July and August of the relevant year. It is supposed that the summer climate had an effect on the prevalence rate of "coughing." In the logistic regression analysis of the individual questionnaire data obtained from some sampled schools, the odds ratios of "residents along heavy-traffic roads" to "coughing" were 1.37〜1.70 (p<0.001) for every survey. Also, a significant correlation was observed between the prevalence rate of "coughing" and the percentage of "residents along heavy-traffic roads". Since there is a strong correlation between the percentage of "residents along heavy-traffic roads" and the atmospheric nitrogen dioxide (NO_2) concentration, it was considered that the percentage was available as the index of motor-vehicle exhaust gas pollution. The percentage of "residents along heavy-traffic roads" and the NO_2 levels in Osaka Prefecture had decreased slightly since 1995. Then, it was suggested that the prevalence rate of "coughing" among children had decreased due to the decline in the NO_2 levels. In addition, the lower limits of the NO_2 levels which have an effect on the "coughing" symptoms of children were estimated to be 0.022〜0.024 ppm in terms of the annual mean value.