Statistical issues in epidemiologic studies of the health effects of ambient acid aerosols

Although the ecologic effects of acid rain have been widely reported, relatively little is known about the effects of acidic air pollution on human health. Some epidemiologic and animal studies suggest, however, that acidity is an important determinant of the respiratory health effects of aerosols. This paper reviews some of that evidence and discusses its implications for the design and analysis of epidemiologic studies. We contrast two types of exposure patterns: peak exposures associated with air pollution episodes, and chronic exposures resulting from persistently high levels of air pollutants. Recent work on the analysis of repeated categorical outcome variables provides new methods for the analysis of episode studies. Studies of long-term exposure require comparisons among population groups, and these comparisons can be subject to the design effects characteristic of multistage sample surveys. We examine the implications of these design effects for epidemiologic studies. Finally, the paper discusses the measurement errors induced by the use of outdoor measurements to quantify personal exposure to air pollutants. Recent work on methods for errors-in-variables problems may aid in assessing the effects of such errors on conventional analyses of air-pollution studies.     

健康风险与喷洒污水产生的喷雾中微生物浓度的关系

与喷洒处理后的生活污水产生的喷雾相关联的细菌健康风险难于控制.在Rolleston 污水处理厂进行喷雾取样,符合取水权条件.Rolleston 采用延时曝气, UV 处理和土地喷雾灌溉.虽然喷洒液中有大肠杆菌,即使采用非选择性媒介,用Andersen 采样器收集不到.在微小杆菌芽孢计数为 1000 /100 ml,在暴露在相当于一个人靠近喷雾器站两小时的空气体积的琼脂皿上只生长出三个菌群.三个芽孢可能没有暴露在空气中,因为可能被污染了.因为存留在空气中的液滴体积较小,微生物存在的机会较低,除非喷洒液中微生物浓度较高.如果排放物中某微生物含量10,000 /100 ml ,则直径100 (m 的颗粒含有一个或多个微生物的机会是0.005% . 进行了野外实验,以确定排放物中微生物数量和喷雾雾珠大小比例关系,该雾珠可能进入人的肺部且含有微生物. 两株小芽孢杆菌是一样的,只对两种抗生素的抵抗力不同,混入水中喷洒.用装有含适当抗生素琼脂皿的几对六级Andersen 采样器收集雾珠/ 颗粒.结果表明,当喷洒悬浮液中芽孢浓度平均大一百倍时,六级Andersen采样器收集(即可能进入人肺)的雾珠/ 颗粒数量平均大五十倍.因此,如果始终(就像食品厂进行有害分析和关键点控制)可检测排放物,确保要喷洒的排放物中致病菌水平始终较低,则对于公共健康风险,这应当是比监测大气更容易更可靠的测试.     

Associations Between Morbidity and Alternative Measures of Particulate Matter

This paper explores the association between acute respiratory morbidity and different measures of exposure to airborne particulate matter, including sulfates, total suspended particulates, and fine and inhalable particulates. Regression analysis was used to test for the impacts of these alternative measures of particulate matter on respiratory morbidity using the 1979-1981 annual Health Interview Surveys and EPA's Inhalable Particle Monitoring Network. The general results indicate that, of the surrogate measures for particulate matter, sulfates appear to have the greatest association with morbidity. To the extent that sulfuric acid aerosols are correlated with airborne sulfates, the results suggest that respiratory impairment sufficient to lead to days of reduced activity may be related to the existence of acidity in the air. These findings are consistent with the results of ecological studies reporting an association between mortality and exposures to fine particles and sulfates.     

感染性气溶胶泄漏环境风险预测模型系统与应用

目的针对高等级生物安全实验室污染物泄漏的环境风险开展理论与技术研究，建立适用于高等级生物安全实验室发生感染性气溶胶泄漏的环境风险预测模型。方法以烟团扩散模型为基础，并结合病原微生物在空气中的传播特性和周边地形条件进行修正，建立了感染性气溶胶泄漏环境风险预测模型系统。结果与结论模拟案例分析表明，在发生极端风险泄漏事故时，实验室周边将出现短暂的高风险区。当大气环境为中性稳定度时，发生感染性气溶胶泄漏事故对环境浓度影响最大。