A new study links heavy air pollution from coal burning to shorter lives in northern China. Researchers estimate that the half-billion people alive there in the 1990s will live an average of 5 years less than their southern counterparts because they breathed dirtier air.

　　一项新的研究表明由于烧煤引发的严重空气污染将缩短中国北方居民的寿命。研究人员估计，因为呼吸更污浊的空气，上世纪90年代居住于北方的5亿居民要比南部的居民平均少活5年。

　　China itself made the comparison possible: for decades, a now-discontinued government policy provided free coal for heating, but only in the colder north. Researchers found significant differences in both particle pollution of the air and life expectancy in the two regions, and said the results could be used to extrapolate the effects of such pollution on lifespans elsewhere in the world.

　　中国可以用自身来做一个比较：几十年来，国家政策只允许给寒冷的北方地区提供免费的煤燃料供暖，现在这项政策已经被废止。研究人员发现，在南北两个地区，空气中颗粒物污染和人们的预期寿命都存在显著差异，而且研究结果可以用来推断在世界其他地方这种污染对寿命的影响。

　　The study by researchers from China, Israel and the United States was published Tuesday in the Proceedings of the National Academy of Sciences.

　　这项研究由来自中国，以色列和美国的研究人员共同完成，并于周二发表在《美国国家科学院院刊》上。

　　While previous studies have found that pollution affects human health, “the deeper and ultimately more important question is the impact on life expectancy,” said one of the authors, Michael Greenstone, a professor of environmental economics at Massachusetts Institute of Technology.

　　虽然之前的研究发现，污染会影响人体健康，但是“更深层和根本上更重要的问题是对预期寿命的影响。”该项研究的作者之一，麻省理工学院环境经济学教授迈克尔·格林斯通说。

　　“This study provides a unique setting to answer the life expectancy question because the (heating) policy dramatically alters pollution concentrations for people who appear to be of otherwise identical health,” Greenstone said in an email. “Further, due to the low rates of migration in China in this period, we can know people’s exposure over long time periods,” he said.

　　“这项研究为回答有关寿命的问题提供了一个独特的情境，因为(供暖)政策极大地改变了看似健康状况相同的人生存环境的污染浓度，”格林斯通在一封电子邮件中说道，“此外，由于中国在此期间的低迁移率，我们就可以知道，人们长期以来都是暴露在一定污染浓度的环境中。”

　　The policy gave free coal for fuel boilers to heat homes and offices to cities north of the Huai River, which divides China into north and south. It was in effect for much of the 1950-1980 period of central planning, and, though discontinued after 1980, it has left a legacy in the north of heavy coal burning, which releases particulate pollutants into the air that can harm human health. Researchers found no other government policies that treated China’s north differently from the south.

　　因淮河为中国区分南北的界限，故之前的政策为中国淮河以北城市的家庭和办公室提供免费的煤燃料锅炉供暖。该政策在中央计划的1950年-1980年期间开始实行，虽然在1980年后被废止，但大量的煤燃烧却给北方的空气留下了危害人体健康的颗粒污染物。研究人员并没有发现其他不同对待中国南北部的政策。

　　The researchers collected data for 90 cities, from 1981 to 2000, on the annual daily average concentration of total suspended particulates. In China, those are considered to be particles that are 100 micrometers or less in diameter, emitted from sources including power stations, construction sites and vehicles.

　　研究人员收集了90个城市多年总悬浮微粒日平均浓度的数据，时间跨度从1981年到2000年。在中国，悬浮微粒被认为是指由包括发电厂、建筑工地和车辆发出的，直径小于或等于100微米的粒子。

　　The researchers estimated the impact on life expectancies using mortality data from 1991-2000. They found that in the north, the concentration of particulates was 184 micrograms per cubic meter ― or 55 percent ― higher than in the south, and life expectancies were 5.5 years lower on average across all age ranges.

　　研究人员通过1991年-2000年的死亡率数据来估计对预期寿命的影响。他们发现，在北方，微粒的浓度为每立方米184微克——比南部数据高55%，而且在所有年龄段的平均预期寿命比南方短5.5年。

　　The researchers said the difference in life expectancies was almost entirely due to an increased incidence of deaths classified as cardiorespiratory ― those from causes that have previously been linked to air quality, including heart disease, stroke, lung cancer and respiratory illnesses.

　　研究人员说，预期寿命的差异几乎完全是由于心肺死亡类疾病的发生率增加——这些通常被人们认为是空气质量导致的疾病包括心脏病、中风、肺癌和呼吸系统疾病。

　　Total suspended particulates include fine particulate matter called PM2.5 ― particles with diameters of no more than 2.5 micrometers. PM2.5 is of especially great health concern because it can penetrate deep into the lungs, but the researchers lacked the data to analyze those tiny particles separately.

　　总悬浮粒子包括被称为PM2.5的细颗粒物，即直径不超过2.5微米的颗粒。因为它可以渗透到肺部深处，PM2.5引起人们对健康的极大担忧，但研究人员缺乏数据来单独分析这些微小颗粒的实际影响。