美國空氣最清新的城市
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.
空氣清潔法實行後40年來，越來越多人呼吸到更加清新的空氣。“總體上，我們見證了空氣質量的巨大改善。”落砂機南加利福尼亞大學全球健康研究所主任Jonathan M. Samet哲學博士說。
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.
不過，一些地方的空氣比其他地方的更加清新。下面是根據美國肺協會的年度報告列出的5個空氣最清新的城市，肺協會觀察了臭氧和微粒物質的含量，這些細微顆粒可能進入肺部。
Cheyenne, Wyo.
Population: 88,854
懷俄明州夏延
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).
夏延是空氣最清新的城市。它全年的微粒含量PM2.5最低，肺部侵略者——微粒PM 2.5是人類頭髮直徑的約30分之一。夏延城市面積小也有幫助；路上來往的車輛更少，機動車是PM2.5的主要來源。
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.
懷俄明州首府的24小時顆粒污染物也曾短期上升。“當接觸達到頂峯，就會增加因患哮喘或心臟病而住院治療的風險。”西雅圖華盛頓大學的職業與環境醫學計劃哲學博士Joel Kaufman說。
Santa Fe, N.M.
Population: 188,210
新墨西哥聖達菲
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.
聖達菲以美術館和清新空氣聞名，所以，一名聖達菲藝術家最近公佈了一個雕刻品，測量空氣顆粒物污染，這一點也不令人驚奇。
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.)
該城市逐漸增加的人羣也引起了對空氣質量的擔憂。嚴格法規限制焚燒木材，木材是微粒物質的來源之一。（這個地區擁有的國家森林超過150萬英畝。）
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.)
聖達菲是美國汽車法律協會（ALA）觀察的臭氧水平一貫在安全範圍的20個城市中唯一的一個。（大氣層中的臭氧保護我們免受陽光的輻射，而地面的臭氧是一種污染物。）
Bismarck, N.D.
Population: 106,286
北達科他州俾斯麥
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.
俾斯麥是美國所有整年微粒物質水平最低的城市之一，而且該城市的臭氧含量也屬於安全水平。
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.
北達科他州首府不受污染物的破壞是由於它相對偏遠的位置，還有它不處於其它城市的下風區的事實。儘管這樣使它冬天成爲美國最冷的城市，但是低溫也預防臭氧的危害。
Its citizens care also helped establish the Bismarck Tobacco Free Coalition to promote a smoke-free environment.
該市市民也積極幫助建立無煙聯盟促進無煙環境。
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.
好事就是這個小，相對遙遠的大瀑布城擁有清新的空氣，給居民們充足時間充分利用這個地區的自然美景，進行戶外活動。
The city continues to work hard to maintain that quality standard, recently fending off a major coal-fired power-plant project.
這個城市繼續努力保持這種空氣質量標準，最近還反對一個重要的煤礦發電廠的計劃。
Honolulu
Population: 907,574
火奴魯魯
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.
火奴魯魯以流行的度假勝地著稱。但是它也是肺病患者的一個度假勝地，因爲它是國家臭氧和微粒物質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.
由於火奴魯魯遠離太平洋，Kaufman教授建議，總體上，它不受需要遠程傳送的污染物的影響。例如，由燃煤引起的微粒物質可以傳播到遠距離，但是極少會傳到火奴魯魯，它離大陸約2000英里。
Large amounts of rain, adds Dr. Samet, also help.
Samet博士還稱，大量降水也有幫助。
