近日，來自哈佛公共衛生學院的研究人員通過研究發現，相比空氣汙染率水平（PM2.5）較地地區生活的65歲以上的老年個體而言，空氣汙染率水平（PM2.5）較高地區生活的個體的死亡率較高，相關研究刊登於國際雜誌Environmental Health Perspectives上；本文研究首次檢測了不同地區空氣中煙塵顆粒對個體機體的影響，同時觀察了細顆粒對機體的損傷效應，研究者表示，這些有害顆粒的濃度還不到環境保護局（EPA）製定的當前標準規定的三分之一。

　　Joel Schwartz教授表示，多數國家可以要麼滿足EPA的標準，要麼在未來幾年爭取達到這樣的標準；但我們的研究卻發現這並不足夠，我們依然需要許多不經過除塵器排放煙塵的燃煤電廠，同時也應當盡量避免交通和木材燃燒帶來的煙塵。

　　此前研究發現短期或長期暴露於PM2.5中和個體死亡率增加的關聯，究其機製研究者發現這跟心髒疾病、血壓增加以及肺部功能降低直接相關；而本文中研究者利用衛星數據來測定新英格蘭每個區域的顆粒水平和溫度，這就可以幫助研究者檢測PM2.5對遠離檢測點的區域的影響，同時也可以幫助觀察個體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年間工隊240萬個體進行了健康數據的追蹤分析。

　　結果發現，短期和長期PM2.5的暴露均和個體死亡率增加直接相關，甚至在有些PM2.5水平低於EPA標準的地區仍然有這樣的關係；在短期暴露（2天）的情況下，隨著PM2.5濃度增加10μg/m3，個體的死亡率就會增加2.14%；而在長期暴露（1年）的情況下，隨著PM2.5濃度增加10μg/m3，個體的死亡率就會增加7.52%。

　　最後研究者Schwartz說道，空氣汙染物中的微粒就好象鉛汙染一樣，目前並沒有證據表明微粒在標準之下的水平是安全的，因此後期我們還需要製定新的策略來盡可能降低個體的暴露風險，從而為改善個體的健康提供一定的幫助。

　　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.