近日，来自哈佛公共卫生学院的研究人员通过研究发现，相比空气污染率水平（PM2.5）较地地区生活的65岁以上的老年个体而言，空气污染率水平（PM2.5）较高地区生活的个体的死亡率较高，相关研究刊登于国际杂志Environmental Health Perspectives上；本文研究首次检测了不同地区空气中烟尘颗粒对个体机体的影响，同时观察了细颗粒对机体的损伤效应，研究者表示，这些有害颗粒的浓度还不到环境保护局（EPA）制定的当前标准规定的三分之一。

　　Joel Schwartz教授表示，多数国家可以要么满足EPA的标准，要么在未来几年争取达到这样的标准；但我们的研究却发现这并不足够，我们依然需要许多不经过除尘器排放烟尘的燃煤电厂，同时也应当尽量避免交通和木材燃烧带来的烟尘。

　　此前研究发现短期或长期暴露于PM2.5中和个体死亡率增加的关联，究其机制研究者发现这跟心脏疾病、血压增加以及肺部功能降低直接相关；而本文中研究者利用卫星数据来测定新英格兰每个区域的颗粒水平和温度，这就可以帮助研究者检测PM2.5对远离检测点的区域的影响，同时也可以帮助观察个体PM2.5的短期暴露以及每年的平均暴露水平，研究者在2003年至2008年间工队240万个体进行了健康数据的追踪分析。

　　结果发现，短期和长期PM2.5的暴露均和个体死亡率增加直接相关，甚至在有些PM2.5水平低于EPA标准的地区仍然有这样的关系；在短期暴露（2天）的情况下，随着PM2.5浓度增加10μg/m3，个体的死亡率就会增加2.14%；而在长期暴露（1年）的情况下，随着PM2.5浓度增加10μg/m3，个体的死亡率就会增加7.52%。

　　最后研究者Schwartz说道，空气污染物中的微粒就好象铅污染一样，目前并没有证据表明微粒在标准之下的水平是安全的，因此后期我们还需要制定新的策略来尽可能降低个体的暴露风险，从而为改善个体的健康提供一定的帮助。

　　doi:10.1289/ehp.1409111

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　　Low-Concentration PM2.5 and Mortality: Estimating Acute and Chronic Effects in a Population-Based Study.

　　Liuhua Shi1, Antonella Zanobetti1, Itai Kloog1,2, Brent A. Coull3, Petros Koutrakis1, Steven J. Melly1, and Joel D. Schwartz1

　　Background: Both short- and long-term exposures to fine particulate matter (PM2.5) are associated with mortality. However, whether the associations exist below the new EPA standards (12 μg/m3 of annual average PM2.5, 35 μg/m3 daily) is unclear. In addition, it is not clear whether results of previous time series studies (fit in larger cities) and cohort studies (fit in convenience samples) are generalizable to the general population. Objectives: To estimate the effects of low-concentration PM2.5 on mortality. Methods: High resolution (1 × 1 km) daily PM2.5 predictions, derived from satellite aerosol optical depth retrievals, were employed. Poisson regressions were applied to the Medicare population (age>=65) in New England to simultaneously estimate the acute and chronic effects, with mutual adjustment for short- and long-term exposure, as well as area-based confounders. Models were also restricted to annual concentrations below 10 μg/m3 or daily concentrations below 30 μg/m3. Results: PM2.5 was associated with increased mortality. In the cohort, 2.14% (95% CI: 1.38, 2.89%) and 7.52% (95% CI: 1.95, 13.40%) increases were estimated for each 10 μg/m3 increase in short- (2 day) and long-term (1 year) exposures, respectively. The associations still held for analyses restricted to low-concentration PM2.5 exposures. The corresponding estimates were 2.14% (95% CI: 1.34, 2.95%) and 9.28% (95% CI: 0.76, 18.52%). Penalized spline models of long-term exposure indicated a higher slope for mortality in association with exposures above versus below 6 μg/m3. In contrast, the association between short-term exposure and mortality appeared to be linear across the entire exposure distribution. Conclusions: Using a mutually adjusted model, we estimated significant acute and chronic effects of PM2.5 exposures below current EPA standards. These findings suggest that improving air quality below current standards may benefit public health.