NIHR HPRU Health Impact of Environmental Hazards, Analytical, Environmental & Forensic Sciences, King's College London, UK.
NIHR HPRU Health Impact of Environmental Hazards, Analytical, Environmental & Forensic Sciences, King's College London, UK.
Environ Int. 2020 Apr;137:105500. doi: 10.1016/j.envint.2020.105500. Epub 2020 Feb 1.
The use of proxy exposure estimates for PM and NO in air pollution studies instead of personal exposures, introduces measurement error, which can produce biased epidemiological effect estimates. Most studies consider total personal exposure as the gold standard. However, when studying the effects of ambient air pollution, personal exposure from outdoor sources is the exposure of interest.
We assessed the magnitude and variability of exposure measurement error by conducting a systematic review of the differences between personal exposures from outdoor sources and the corresponding measurements for ambient concentrations in order to increase understanding of the measurement error structures of the pollutants.
We reviewed the literature (ISI Web of Science, Medline, 2000-2016) for English language studies (in any age group in any location (NO) or Europe and North America (PM)) that reported repeated measurements over time both for personal and ambient PM or NO concentrations. Only a few studies reported personal exposure from outdoor sources. We also collected data for infiltration factors and time-activity patterns of the individuals in order to estimate personal exposures from outdoor sources in every study.
Studies using modelled rather than monitored exposures were excluded. Type of personal exposure monitor was assessed. Random effects meta-analysis was conducted to quantify exposure error as the mean difference between "true" and proxy measures.
Thirty-two papers for PM and 24 for NO were identified. Outdoor sources were found to contribute 44% (range: 33-55%) of total personal exposure to PM and 74% (range: 57-88%) to NO. Overall estimates of personal exposure (24-hour averages) from outdoor sources were 9.3 μg/m and 12.0 ppb for PM and NO respectively, while the corresponding difference between these exposures and the ambient concentrations (i.e. the measurement error) was 5.72 μg/m and 7.17 ppb. Our findings indicated also higher error variability for NO than PM. Large heterogeneity was observed which was not explained sufficiently by geographical location or age group of the study sample.
LIMITATIONS, CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS: Relying only on information available in published studies led to some limitations: the contribution of outdoor sources to total personal exposure for NO had to be inferred, individual variation in exposure misclassification was unavailable and instrument error could not be addressed. The larger magnitude and variability of errors for NO compared with PM has implications for biases in the health effect estimates of multi-pollutant epidemiological models. Results suggest that further research is needed regarding personal exposure studies and measurement error bias in epidemiological models.
在空气污染研究中，使用代理暴露估计值（PM 和 NO）代替个人暴露值会引入测量误差，从而导致流行病学效应估计值产生偏差。大多数研究都将总个人暴露值视为金标准。然而，在研究环境空气污染的影响时，人们更感兴趣的是来自室外源的个人暴露值。
我们通过系统地回顾室外个人暴露值与相应的环境浓度测量值之间的差异，评估暴露测量误差的大小和可变性，以便更好地了解污染物测量误差结构。
我们检索了文献（ISI Web of Science、Medline，2000-2016 年），纳入了报告时间序列内个人和环境 PM 或 NO 浓度重复测量的英语语言研究（任何年龄组、任何地点（NO）或欧洲和北美（PM））。只有少数研究报告了来自室外源的个人暴露值。我们还收集了个体渗透因子和时活动模式的数据，以便估算每个研究中来自室外源的个人暴露值。
排除了使用模型而非监测暴露值的研究。评估了个人暴露监测器的类型。采用随机效应荟萃分析量化暴露误差，即“真实”和代理测量值之间的平均差异。
共确定了 32 篇关于 PM 的论文和 24 篇关于 NO 的论文。结果发现，室外源对 PM 的总个人暴露值的贡献为 44%（范围：33-55%），对 NO 的贡献为 74%（范围：57-88%）。室外源个人暴露值（24 小时平均值）分别为 PM 9.3μg/m 和 NO 12.0 ppb，而这些暴露值与环境浓度之间的差异（即测量误差）分别为 5.72μg/m 和 7.17 ppb。我们的研究结果还表明，NO 的测量误差变异性高于 PM。观察到较大的异质性，但地理位置或研究样本的年龄组无法充分解释这种异质性。
局限性、结论和关键发现的意义：仅依赖于已发表研究中的信息会带来一些局限性：NO 总个人暴露值中室外源的贡献必须推断得出，个体暴露分类错误的个体差异不可用，仪器误差也无法解决。与 PM 相比，NO 的测量误差幅度和变异性更大，这对多污染物流行病学模型的健康效应估计值产生了偏差。结果表明，需要进一步研究个人暴露研究和流行病学模型中的测量误差偏差。
