美国肺科协会本周三发布的一份报告称，虽然绿色行动和旨在提高空气质量的法律在不断推行，但仍有60％的美国人生活在不利健康的被污染空气中。该协会根据2005年到2007年间美国各州和地方机构向美国环境保护局提交的空气检测结果，对美国各城市和县镇的空气污染水平进行了排名。该报告指出，几乎每一个美国大城市的空气污染水平都达到对健康不利的程度，而居住在这些地区的美国人达到1.861亿。

Sixty percent of Americans live in areas with unhealthy air pollution levels, despite a growing green movement and more stringent¹ laws aimed at improving air quality, the American Lung Association said in a report released Wednesday.

The public-health group ranked the pollution levels of US cities and counties based on air quality measurements that state and local agencies reported to the US Environmental Protection Agency between 2005 and 2007.

Overall, the report found that air pollution at times reaches unhealthy levels in almost every major city and that 186.1 million people live in those areas. The number is much higher than last year's figure of about 125 million people because recent changes to the federal ozone² standard mean more counties recognize unhealthy levels of pollution.

Health effects from air pollution include changes in lung function, coughing, heart attacks, lung cancer and premature³ death.

"Six out of 10 Americans right now as we speak live in areas where the air can be dirty enough to send people to the emergency room, dirty enough to shape how kids' lungs develop and even dirty enough to kill," said Janice E. Nolen, the association's assistant vice⁴ president on national policy and advocacy.

Cities including Los Angeles, New York, Atlanta, Charlotte, Philadelphia, Washington D.C. and Baltimore have seen improvements in air quality over the last decade, the report said.

The Los Angeles-Long Beach-Riverside region of Southern California remained the metropolitan⁶ area with the highest levels of ozone pollution, as it has in each of the past 10 reports. Other metropolitan areas considered to have the most ozone pollution included Houston-Baytown-Huntsville and Dallas-Fort Worth in Texas.

The areas with the most short-term particle pollution or soot⁷ were Pittsburgh-New Castle, Pa.; and the California areas of Fresno-Madera, Bakersfield and Los Angeles-Long Beach-Riverside.

The cleanest metro⁵ area in all categories was Fargo, N.D.

The rankings in the "State of the Air Report" were based on ozone pollution levels produced when heat and sunlight come into contact with pollutants⁸ from power plants, cars, refineries⁹ and other sources.

The lung association also studied short-term and year-round levels of particle pollution, which is made up of a mix of tiny solid and liquid particles in the air.

Vocabulary:

at times: on occasion; sometimes （有时）

particle pollution: 颗粒物污染