国家环境空气质量标准规定了全国的二氧化硫浓度限值来保护人民健康。
NAAQS (National Ambient Air Quality Standards) define attainment and protect human health by setting a limit on SO2 concentration nationwide.
在1997年，美国环保署就首次制定了年度，和24小时国家环境空气质量标准来监测PM 2.5。
In 1997, EPA established annual and 24-hour NAAQS for PM2.5 for the first time.
2004年，受监测的342个城市中有210个城市的空气质量超过了国家环境空气质量标准的二级标准。
In 2004, 210 cities exceeded the Class 2 limit values of the National Ambient Air Quality Standard (NAAQS) within the total 342 monitored cities.
自1970年制定之后，国家环境空气质量标准评审流程已经逐步形成，并且呈现许多当前特征业已存在了20多年。
This NAAQS review process has evolved since it was instituted in 1970, with many of the current features having been in place for over 20 years.
根据环境保护部对全国338个城市的调查，2016年，只有四分之一的中国城市达到了国家的空气质量标准。
In 2016, only one fourth of Chinese cities met the country's air quality standards, according to a survey of 338 cities nationwide from the Ministry of Environmental Protection.
按照国家实施严格的空气质量标准后需求的不断增加，中国应该加快研发环境空气监测设备。
China should speed up the research and development on air monitoring equipment in line with the rising demand after the country puts in place stricter air quality standards.
根据一篇科学期刊文章表示，只有9％的中国人生活在符合国家空气质量标准的环境下。 。
Only 9 percent of people in China live in an environment that meets the national air quality standards, according to a scientific journal article.
根据一篇科学期刊文章表示，只有9％的中国人生活在符合国家空气质量标准的环境下。 。
Only 9 percent of people in China live in an environment that meets the national air quality standards, according to a scientific journal article.
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