Back in 1970, Los Angeles was known as the smog capital of the world — a notorious example of industrialization largely unfettered by regard for health or the environment. Heavy pollution drove up respiratory and heart problems and shortened lives.

在1970年，洛杉矶曾被称为“世界光化学烟雾之都”，它是一个不太考虑健康和环境因素，大肆进行工业化建设的臭名昭著的例子。严重的污染加重了呼吸道和心脏疾病的问题，也缩短了人们的寿命。

But 1970 was also the year the environmental movement held the first Earth Day and when, 45 years ago this month, Congress passed a powerful update of the Clean Air Act. (Soon after, it was signed by President Richard Nixon, and it was followed by the formation of the Environmental Protection Agency and passage of the Clean Water Act, making him one of the most important, though underappreciated, environmentalists in American history.)

但也是在1970年，环保运动人士第一次举行了“世界地球日”(Earth Day)。而且在45年前的9月，国会通过了颇具影响力的新《清洁空气法》(Clean Air Act)。不久以后，理查德·尼克松(Richard Nixon)总统正式签署了该法案，之后美国国家环境保护局（Environmental Protection Agency，简称EPA）成立，《清洁水法案》(Clean Water Act)也获得通过。尼克松因此称得上是美国历史上最重要的环保人士之一，尽管他在这方面的成就没有得到充分的认可。

Since that time, the Clean Air Act has repeatedly been challenged as costly¹ and unnecessary. As a fight brews² over President Obama’s new use of the law to address global warming, it’s worth re-examining the vast difference the law has already made in the quality of the air we breathe, and in the length of our lives.

从那个时候开始，《清洁空气法》就反复受到挑战，它被认为成本高且不必要。在奥巴马总统和民主党正酝酿重新利用这一法案解决全球变暖问题时，有必要来重新审视一下，这项法案给我们呼吸的空气质量和预期寿命带来了怎样的巨大改变。

Numerous studies have found that the Clean Air Act has substantially improved air quality and averted³ tens of thousands of premature⁴ deaths from heart and respiratory disease. Here, I offer new estimates of the gains in life expectancy⁵ due to the improvement in air quality since 1970 — based on observations from the current “smog capital” of the world, China. (To learn more about how this was calculated, click here.)

有许多研究发现，《清洁空气法》大幅提高了空气质量，让数以万计的人免于因心脏和呼吸道疾病而提早死亡。在这里，我对自1970年以来因空气质量改善而实现的预期寿命增长，提供一些最新的估算数据，其中参照了对当今的世界“雾霾之都”中国的观察（了解有关该估算方式的更多信息，请点击这里）。

For several decades starting in the 1950s, China’s government gave residents in the northern half of the country free coal for winter heating, effectively creating a natural experiment in the health impact of pollution. My colleagues and I recently compared pollution and mortality rates between the north south of China and calculated the toll⁶ of airborne particulate⁷ matter, widely believed to be the most harmful form of air pollution, on life expectancy.

从1950年代开始的几十年里，中国政府给华北地区的居民提供免费的煤块用来冬天取暖，这实际上构成了一个观察污染对健康的影响的天然实验。我和同事最近比较了中国南北方污染和死亡率数据的差异，计算出悬浮颗粒物质导致的死亡人数。普遍认为悬浮颗粒物是对人类寿命危害最大的空气污染物。

Applying that formula to E.P.A. particulate data from 1970 to 2012 yields striking results for American cities.

将EPA统计的1970年到2012年间的颗粒物质数据，用同一公式计算，就得到了关于美国城市的惊人数据。

In Los Angeles, particulate pollution has declined by more than half since 1970. The average Angeleno lives about a year and eight months longer. Residents of New York and Chicago have gained about two years on average. With more than 42 million people currently living in these three metropolitan⁸ areas, the total gains in life expectancy add up quickly.

在洛杉矶，颗粒物质污染自1970年以来减少了超过一半。洛杉矶人的平均寿命延长了大约一年零八个。纽约和芝加哥的居民平均寿命延长了大约两年。超过4200万人目前居住在这三大都市圈，整体预期寿命的延长，积累起来颇为可观。

But some of the greatest improvements occurred in smaller towns and cities where heavy industries appeared to operate with few restrictions⁹ on pollution.

但状况改善最明显的其实是一些规模更小的城镇，在那里经营的重工业企业，以前似乎不会受到任何污染方面的监管。

In 1970, the Weirton, W.Va.–Steubenville, Ohio, metropolitan area had particulate concentrations similar to current-day Beijing. A child born there today can expect to live about five years longer than one born in 1970.

1970年，西弗吉尼亚州的韦尔顿(Weirton)和俄亥俄州的斯托本维尔(Steubenville)区域，存在悬浮颗粒浓度高的问题，与如今北京的状态类似。现在出生在那里的孩子，预计可以比1970年出生在那里的孩子，多活大约五年。

More than 200 million people currently live in places monitored for particulates¹⁰ in 1970 and today. (The E.P.A. focuses on the most heavily populated or polluted areas of the country, which is why these calculations exclude approximately 115 million people.) On average, these people can expect to live an additional 1.6 years, for a total gain of more than 336 million life-years.

现在，有2亿多人口生活在1970年和现在都有悬浮颗粒数据监测的地区（EPA主要关注美国人口密集或污染严重的地区，因此有大约1.15亿人口不在计算范围内）。平均而言，这2亿人预计可以多活1.6年，这些人口增加的寿命长度总计超过3.36亿年。

Not all of these benefits came from Clean Air Act regulations. Other factors include local regulations and the shifting of relatively¹¹ dirty industries abroad. But the Clean Air Act was a primary cause.

实现这些改变不能仅仅归功于《清洁空气法》的实施。一些地方法规和一些污染相对严重的产业被转移到国外等因素，也发挥了作用。但《清洁空气法》的确是主要原因。

The history and impact of the Clean Air Act can serve as a valuable case study for countries that are struggling today with the extraordinary pollution that we once faced. In Northern China, where pollution is curtailing¹² lives by an average of five years, the government has at last declared a “war on pollution.” While enforcement is not perfect, the government has improved transparency and amended¹³ environmental protection laws to impose stricter punishments against polluters.

清洁空气法》的历史和影响，可以为正在努力解决我们也曾面临过的严重污染问题的那些国家，提供有价值的研究案例。在中国北部地区，环境污染现在让人们的寿命平均缩短了五年，中国政府终于宣布开启“治理污染之战”。尽管执行得并不完美，但中国政府已经提高了透明度，也修订了环境保护法，对污染环境者采取更严厉的惩罚。

In India, pollution is abridging¹⁴ the average person’s life by about three years. But the growing outrage¹⁵ has not yet coalesced¹⁶ into forceful action, although it’s possible that pressure to take steps against climate change will also have an effect on improving air quality.

在印度，环境污染现在让人们的平均寿命降低了大约三年。但民众日益加剧的不满，尚未促使政府采取有力行动。不过，采取措施应对气候变化的压力，可能也会对改善空气质量产生影响。

The hundreds of millions of life-years saved from improved air quality in our country didn’t happen by accident or overnight. This happened because a collective voice for change brought about one of the most influential¹⁷ laws of the land.

在美国，因空气质量提高而延长的总计数亿年寿命，并非偶然实现，也不是一蹴而就，而是因为民众集体发声，要求做出改变，才促成了这个国家最有影响力的法律之一。

As the United States and other nations continue to debate the costs of environmental regulation, they can do so with the knowledge that the benefits can be substantial. As proof, we need look no further than the five extra years residents of Weirton-Steubenville are living and the hundreds of millions of years gained by Americans throughout the nation.

在美国和其他国家继续就环境法规的成本进行辩论时，他们需要了解，这么做的益处是非常可观的。只要看看韦尔顿-斯托本维尔区域的居民因环境改善而多出的五年寿命，以及全国民众整体增加的数亿年寿命，就足以明白这一点。