Valberg Peter A
Gradient Corporation, Cambridge, MA, U.S.A.
Nonlinearity Biol Toxicol Med. 2003 Oct;1(4):521-30. doi: 10.1080/15401420390271137.
Numerous studies of populations living in areas with good air quality have reported correlations between daily average levels of ambient particulate matter (PM) and daily mortality rates. These associations persist at PM levels below current air quality standards and are difficult to reconcile with the toxicology of PM chemical constituents. The unusual level of lethality per unit PM mass predicted by these associations may result from confounding by unmeasured societal, behavioral, or stress factors. Daily average ambient PM levels may be expected to correlate with societal activity level, because a working population increases PM emissions through increased manufacture, power utilization, construction, demolition, farming, and travel. Also, people's perceived and actual health depend on societal and psychological factors. A stress such as anger strongly increases the risk of death due to heart attack. Societal factors modify mortality as shown by calendar-related changes in mortality that are unrelated to air quality. Cardiovascular and respiratory mortality are correlated to day of the week, end of the month, and to the first week of the year. There is likely a role of such nontoxicologic variables in the PM associations, and without vigorously testing if other variables correlate as well as PM, we may erroneously conclude that reducing already low levels of PM will yield real public health benefits.
众多针对生活在空气质量良好地区人群的研究报告了环境颗粒物（PM）日均水平与每日死亡率之间的相关性。这些关联在PM水平低于当前空气质量标准时依然存在，且难以与PM化学成分的毒理学相协调。这些关联所预测的单位PM质量的异常致死水平可能源于未测量的社会、行为或压力因素造成的混杂。预计环境PM日均水平会与社会活动水平相关，因为工作人群会通过增加制造、电力使用、建筑、拆除、农业和出行等活动来增加PM排放。此外，人们的感知健康和实际健康取决于社会和心理因素。诸如愤怒之类的压力会大幅增加因心脏病发作而死亡的风险。如与日历相关的死亡率变化（与空气质量无关）所示，社会因素会改变死亡率。心血管和呼吸系统死亡率与一周中的日期、月末以及一年中的第一周相关。在PM关联中，此类非毒理学变量可能起到了作用，而且如果不积极测试其他变量是否与PM具有同样的相关性，我们可能会错误地得出结论，即降低本就很低的PM水平将产生切实的公共卫生效益。
