Exposure to atmospheric particulate matter (PM) exacerbates respiratory and cardiovascular conditions and is a leading source of premature mortality globally. Organic aerosol contributes a significant fraction of PM in the United States. Here, using surface observations between 1990 and 2012, we show that organic carbon has declined dramatically across the entire United States by 25–50%; accounting for more than 30% of the US-wide decline in PM. The decline is in contrast with the increasing organic aerosol due to wildfires and no clear trend in biogenic emissions. By developing a carbonaceous emissions database for the United States, we show that at least two-thirds of the decline in organic aerosol can be explained by changes in anthropogenic emissions, primarily from vehicle emissions and residential fuel burning. We estimate that the decrease in anthropogenic organic aerosol is responsible for averting 180,000 (117,000–389,000) premature deaths between 1990 and 2012. The unexpected decrease in organic aerosol, likely a consequence of the implementation of Clean Air Act Amendments, results in 84,000 (30,000–164,000) more lives saved than anticipated by the EPA between 2000 and 2010.

中文翻译：

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美国大气有机气溶胶减少的原因和后果


暴露于大气颗粒物 (PM) 会加剧呼吸系统和心血管疾病，是全球过早死亡的主要原因。在美国，有机气溶胶占 PM 的很大一部分。在这里，通过 1990 年至 2012 年间的地面观测，我们发现整个美国的有机碳急剧下降了 25-50%；占全美PM降幅的30%以上。这一下降与野火导致的有机气溶胶增加形成鲜明对比，且生物排放没有明显趋势。通过为美国开发碳排放数据库，我们表明，至少三分之二的有机气溶胶下降可以通过人为排放的变化来解释，主要来自车辆排放和住宅燃料燃烧。我们估计，1990 年至 2012 年间，人为有机气溶胶的减少避免了 180,000 人（117,000–389,000）人过早死亡。有机气溶胶的意外减少可能是实施《清洁空气法修正案》的结果，导致 84,000 人（30,000 人）过早死亡。 2000 年至 2010 年间，拯救的生命比 EPA 预期的要多 –164,000 人。