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

1973年至2003年期间，在大阪府所有公立小学儿童中，每隔两年或三年共进行了15次关于主观症状的问卷调查。自1983年以来，儿童中“咳嗽”的患病率一直保持在相同的水平，约为10%。“咳嗽”的患病率(10月调查)与有关年份7、8月的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。对抽样调查学校的个人问卷资料进行Logistic回归分析，每次调查“交通繁忙路旁居民”与“咳嗽”的优势比为1.3 7~1.7(p&lt；0.001)。此外，“咳嗽”的患病率与“交通繁忙的道路上的居民”的比例之间也存在显著的相关性。由于“交通繁忙路段居民”的百分比与大气中的二氧化氮(NO2)浓度有很强的相关性，因此认为该百分比可以作为机动车尾气污染的指标。自1995年以来，大阪府“交通繁忙路段居民”的比例和NO_2水平略有下降。结果表明，由于NO2水平的下降，儿童咳嗽患病率有所下降。此外，对儿童咳嗽症状有影响的NO2水平的年平均值下限估计为0.022~0.024 ppm。

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.