Clean air act amendment ( 1987 ) established a national air - quality standard for ozone 1987年洁净空气法修正案建立了空气的国家空气质量标准。
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Clean air act amendment ( 1977 ) established new deadlines for cleaning up polluted areas ; also required review of existing air - quality standards 1977年洁净空气法修正案确定了清理被污染区域的新期限，同时要求对现行空气质量标准进行评估。
