美国空气最清新的城市

Forty years after the Clean Air Act, more people are breathing easier. "In general, we’ve seen tremendous improvement in air quality," says Jonathan M. Samet, MD, director of the Institute for Global Health at the University of Southern California, in Los Angeles.

空气清洁法实行后40年来，越来越多人呼吸到更加清新的空气。“总体上，我们见证了空气质量的巨大改善。”落砂机南加利福尼亚大学全球健康研究所主任Jonathan M. Samet哲学博士说。

But some air is cleaner than others. Here are the 5 cities with the cleanest air, according to the American Lung Association’s annual report, which looks at levels of ozone and particulates, which are tiny particles that can get lodged in your lungs.

不过，一些地方的空气比其他地方的更加清新。下面是根据美国肺协会的年度报告列出的5个空气最清新的城市，肺协会观察了臭氧和微粒物质的含量，这些细微颗粒可能进入肺部。

Cheyenne, Wyo.

Population: 88,854

怀俄明州夏延

人口：8 8854

Cheyenne is the clear winner: It has the lowest level of year-round PM 2.5 particulates, tiny lung invaders about 1/30th the width of a human hair. Cheyenne's small size may help; fewer cars travel the roads, and vehicles are a key source of PM 2.5 (and ozone).

夏延是空气最清新的城市。它全年的微粒含量PM2.5最低，肺部侵略者——微粒PM 2.5是人类头发直径的约30分之一。夏延城市面积小也有帮助；路上来往的车辆更少，机动车是PM2.5的主要来源。

Wyoming’s capital also has fewer short-term spikes in 24-hour particle pollution. "When exposure peaks, you can have an increased risk of hospitalization for asthma or a heart attack," notes Joel Kaufman, MD, director of the Occupational and Environmental Medicine Program at the University of Washington, in Seattle.

怀俄明州首府的24小时颗粒污染物也曾短期上升。“当接触达到顶峰，就会增加因患哮喘或心脏病而住院治疗的风险。”西雅图华盛顿大学的职业与环境医学计划哲学博士Joel Kaufman说。

Santa Fe, N.M.

Population: 188,210

新墨西哥圣达菲

人口：18 8210

Popular for both its art galleries and clean air, it may come as no surprise that a Santa Fe artist recently unveiled a sculpture that measures particulate air pollution.

圣达菲以美术馆和清新空气闻名，所以，一名圣达菲艺术家最近公布了一个雕刻品，测量空气颗粒物污染，这一点也不令人惊奇。

The city’s growing population cares about air quality too. There are strict rules that limit wood burning, a source of particulates. (The area has more than 1.5 million acres of national forest.)

该城市逐渐增加的人群也引起了对空气质量的担忧。严格法规限制焚烧木材，木材是微粒物质的来源之一。（这个地区拥有的国家森林超过150万英亩。）

Santa Fe is one of only 20 U.S. cities the ALA looked at with consistently safe ozone levels. (While the atmosphere’s ozone protects us from the sun’s rays, ground-level ozone is a pollutant.)

圣达菲是美国汽车法律协会（ALA）观察的臭氧水平一贯在安全范围的20个城市中唯一的一个。（大气层中的臭氧保护我们免受阳光的辐射，而地面的臭氧是一种污染物。）

Bismarck, N.D.

Population: 106,286

北达科他州俾斯麦

人口：10 6286

Bismarck has some of the lowest year-round particulate levels of all U.S. cities (it comes in at number 11) and ozone levels below what is considered dangerous.

俾斯麦是美国所有整年微粒物质水平最低的城市之一，而且该城市的臭氧含量也属于安全水平。

North Dakota’s capital is protected from pollutants due to a relatively remote location and the fact that it’s not downwind of other cities. Although its winters make it one of the coldest U.S. cities, the low temperatures keep ozone at bay.

北达科他州首府不受污染物的破坏是由于它相对偏远的位置，还有它不处于其它城市的下风区的事实。尽管这样使它冬天成为美国最冷的城市，但是低温也预防臭氧的危害。

Its citizens care also helped establish the Bismarck Tobacco Free Coalition to promote a smoke-free environment.

该市市民也积极帮助建立无烟联盟促进无烟环境。

Great Falls, Mont.

Population: 82,178

蒙大拿州大瀑布城

人口：8 2178

It’s a good thing that the small and relatively remote city of Great Falls enjoys clean air, given how much time its residents probably spend outdoors taking advantage of the area’s natural beauty.

好事就是这个小，相对遥远的大瀑布城拥有清新的空气，给居民们充足时间充分利用这个地区的自然美景，进行户外活动。

The city continues to work hard to maintain that quality standard, recently fending off a major coal-fired power-plant project.

这个城市继续努力保持这种空气质量标准，最近还反对一个重要的煤矿发电厂的计划。

Honolulu

Population: 907,574

火奴鲁鲁

人口：90 7574

Honolulu is well-known as a popular vacation destination. But it can be a vacation for the lungs too, as it has some of the nation’s lowest levels of both ozone and particulates.

火奴鲁鲁以流行的度假胜地著称。但是它也是肺病患者的一个度假胜地，因为它是国家臭氧和微粒物质含量最低的城市之一。

Due to Honolulu’s isolation in the Pacific Ocean, Dr. Kaufman suggests that it generally remains safe from the long-range transport of pollution. Particles that result from burning coal, for example, can travel great distances, but few are likely to reach Honolulu, some 2,000 miles off the mainland.

由于火奴鲁鲁远离太平洋，Kaufman教授建议，总体上，它不受需要远程传送的污染物的影响。例如，由燃煤引起的微粒物质可以传播到远距离，但是极少会传到火奴鲁鲁，它离大陆约2000英里。

Large amounts of rain, adds Dr. Samet, also help.

Samet博士还称，大量降水也有帮助。