Kostrzewa Aude, Reungoat Patrice, Raherison Chantal
Laboratoire Santé Travail Environnement (LSTE), EA 3672, ISPED-Université Victor Segalen Bordeaux 2, Case 11, 146 Rue Léo Saignat, 33076 Bordeaux Cedex, France.
Environ Res. 2009 Aug;109(6):651-6. doi: 10.1016/j.envres.2009.05.007.
Fine particles (PM(2.5)) are an important component of air pollution. Epidemiological studies have shown health effects due to ambient air particles, particularly allergies in children. Since the main difficulty is to determine exposure to such pollution, traffic air pollutant (TAP) dispersions models have been developed to improve the estimation of individual exposure levels. One such model, the ExTra index, has been validated for nitrogen oxide concentrations but not for other pollutants. The purpose of this study was to assess the validity of the ExTra index to assess PM(2.5) exposure.
We compared PM(2.5) concentrations calculated by the ExTra index to reference measures (passive samplers situated under the covered part of the playground), in 15 schools in Bordeaux, in 2000. First, we collected the input data required by the ExTra index: background and local pollution depending on traffic, meteorology and topography. Second, the ExTra index was calculated for each school. Statistical analysis consisted of a graphic description; then, we calculated an intraclass correlation coefficient.
Concentrations calculated with the ExTra index and the reference method were similar. The ExTra index underestimated exposure by 2.2 microg m(-3) on average compared to the reference method. The intraclass correlation coefficient was 0.85 and its 95% confidence interval was [0.62; 0.95].
The results suggest that the ExTra index provides an assessment of PM(2.5) exposure similar to that of the reference method. Although caution is required in interpreting these results owing to the small number of sites, the ExTra index could be a useful epidemiological tool for reconstructing individual exposure, an important challenge in epidemiology.
细颗粒物（PM2.5）是空气污染的重要组成部分。流行病学研究表明，环境空气中的颗粒物会对健康产生影响，尤其是对儿童的过敏反应。由于主要困难在于确定此类污染的暴露情况，因此已开发出交通空气污染物（TAP）扩散模型，以改进个体暴露水平的估算。其中一个模型，即ExTra指数，已针对氮氧化物浓度进行了验证，但尚未针对其他污染物进行验证。本研究的目的是评估ExTra指数评估PM2.5暴露的有效性。
2000年，我们在波尔多的15所学校中，将ExTra指数计算得出的PM2.5浓度与参考测量值（位于操场有遮盖部分下方的被动采样器）进行了比较。首先，我们收集了ExTra指数所需的输入数据：取决于交通、气象和地形的背景污染和本地污染。其次，为每所学校计算ExTra指数。统计分析包括图形描述；然后，我们计算了组内相关系数。
用ExTra指数和参考方法计算出的浓度相似。与参考方法相比，ExTra指数平均低估暴露量2.2微克/立方米。组内相关系数为0.85，其95%置信区间为[0.62；0.95]。
结果表明，ExTra指数提供的PM2.5暴露评估与参考方法类似。尽管由于研究地点数量较少，在解释这些结果时需要谨慎，但ExTra指数可能是重建个体暴露的有用流行病学工具，这是流行病学中的一项重要挑战。
