NAAQS (National Ambient Air Quality Standards) define attainment and protect human health by setting a limit on SO2 concentration nationwide.

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。

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The reference for formulating Chinese environmental quality standards is provided by analyzing the formulating procedure and process on ambient air quality standard in EC.

通过分析欧盟环境空气质量标准的制订过程，为我国环境质量标准的制订提供参考与借鉴。

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In the United States, national ambient air quality standards have led to efforts to reduce human emissions that cause pollution.

CNN: Canadian forest fires add to U.S. pollution