Wordley J, Walters S, Ayres J G
Department of Public Health and Epidemiology, University of Birmingham Medical School.
Occup Environ Med. 1997 Feb;54(2):108-16. doi: 10.1136/oem.54.2.108.
To determine the presence and magnitude of any relation between short term variations in ambient concentrations of particulate matter under 10 microns in diameter (PM10) and hospital admissions and mortality in Birmingham, United Kingdom. To find the relative risk associated with various concentrations of PM10, and to estimate the potential public health benefit of reducing PM10 to below various thresholds.
Retrospective ecological study. Air pollution data were taken from a national network monitoring station between 1 April 1992 and 31 March 1994, and weather data for the same period from the University of Birmingham Weather Service. Daily total hospital admissions for the same period for asthma, bronchitis, pneumonia, chronic obstructive pulmonary disease (COPD), acute ischaemic heart disease, acute cerebrovascular disease, all respiratory conditions, and all circulatory conditions were obtained from the West Midlands Regional Health Authority, as well as daily total deaths from 1 April 1992 to 31 December 1994 for chronic obstructive pulmonary disease, pneumonia, all respiratory diseases, all circulatory diseases, and all causes. Multiple linear regression models were constructed after adjusting for confounding factors (day of week, month, linear trend, relative humidity, and temperature). Relative risk of admission at various thresholds of PM10 was calculated with the model, by comparing risk of admission over the threshold with mean risk of admission over the whole period. Potential public health benefits at various thresholds were calculated with the model to predict the number of admissions of deaths that could be saved if, on each day that the PM10 had exceeded that threshold, it had instead been kept at the threshold level.
Significant associations were found between all respiratory admissions, cerebrovascular admissions, and bronchitis admissions and PM10 on the same day. Pneumonia, all respiratory admissions, and asthma admissions were significantly associated with the mean PM10 values for the past three days. Deaths from COPD, all circulatory deaths, and all causes mortality were significantly associated with PM10 24 hours previously, and COPD deaths also with PM10 on the same day. The effect of a 10 micrograms/m3 rise in PM10 was estimated to represent a 2.4% increase in respiratory admissions, a 2.1% increase in cerebrovascular admissions, and a 1.1% increase in all causes mortality. In a population of 1 million, this would represent 0.5 extra respiratory admissions and 0.3 extra deaths. The increase in relative risk was linear without evidence of a threshold. The impact of reducing PM10 to below 70 micrograms/m3 would be small, representing less than 0.1% of respiratory admissions and 0.2% all causes mortality. The impact would be greater at lower thresholds.
Ambient outdoor concentrations of PM10 in the United Kingdom are significantly associated with several indicators of acute health effect. These associations are similar to and consistent with other studies. However, the estimated size of the public health effect is small, accounting for only a small proportion of hospital admissions and mortality over a two year period.
确定英国伯明翰市直径小于10微米的颗粒物（PM10）环境浓度的短期变化与医院收治情况及死亡率之间是否存在关联及其关联程度。找出与不同浓度PM10相关的相对风险，并估计将PM10浓度降至不同阈值以下可能带来的公共卫生效益。
回顾性生态学研究。空气污染数据取自1992年4月1日至1994年3月31日的一个全国性网络监测站，同期的气象数据来自伯明翰大学气象服务中心。同一时期哮喘、支气管炎、肺炎、慢性阻塞性肺疾病（COPD）、急性缺血性心脏病、急性脑血管疾病、所有呼吸道疾病及所有循环系统疾病的每日医院总收治人数，由西米德兰兹地区卫生局提供，1992年4月1日至1994年12月31日COPD、肺炎、所有呼吸道疾病、所有循环系统疾病及所有病因的每日总死亡人数也由该局提供。在对混杂因素（星期几、月份、线性趋势、相对湿度和温度）进行调整后构建多元线性回归模型。通过将超过阈值时的收治风险与整个时期的平均收治风险进行比较，利用该模型计算不同PM10阈值下的收治相对风险。利用该模型计算不同阈值下的潜在公共卫生效益，以预测如果在PM10超过该阈值的每一天，其浓度都保持在阈值水平，可避免的收治和死亡人数。
发现当日所有呼吸道疾病收治、脑血管疾病收治及支气管炎收治与PM10之间存在显著关联。肺炎、所有呼吸道疾病收治及哮喘收治与过去三天的平均PM10值显著相关。COPD死亡、所有循环系统疾病死亡及所有病因死亡率与24小时前的PM10显著相关，COPD死亡也与当日的PM10相关。估计PM10每升高10微克/立方米，呼吸道疾病收治增加2.4%，脑血管疾病收治增加2.1%，所有病因死亡率增加1.1%。在100万人口中，这将意味着呼吸道疾病收治增加0.5例，死亡增加0.3例。相对风险的增加呈线性，无阈值证据。将PM10降至70微克/立方米以下的影响较小，占呼吸道疾病收治的比例不到0.1%，占所有病因死亡率的比例为0.2%。在较低阈值下影响会更大。
英国室外环境中PM10浓度与多种急性健康效应指标显著相关。这些关联与其他研究相似且一致。然而，估计的公共卫生效应规模较小，仅占两年期间医院收治和死亡人数的一小部分。
