Cleaner skies Particulate air pollution in the contiguous United States has decreased considerably over recent decades, but where exactly has that progress been made? Colmer et al. analyzed 36 years of data and found that the spatial distribution of fine particulate matter concentrations has remained largely unchanged over that interval (see the Perspective by Ma). Although, fine particulate pollution levels have dropped overall, those areas that were most and least polluted in 1981 remain so today. We may have made important strides in pollution control, but we have been less successful in addressing disparities of exposure between communities. Science, this issue p. 575; see also p. 503 Particulate air pollution in the United States has fallen substantially over the past four decades, but the relative pattern persists. Air pollution at any given time is unequally distributed across locations. Average concentrations of fine particulate matter smaller than 2.5 micrometers in diameter (PM2.5) have fallen over time. However, we do not know how the spatial distribution of PM2.5 has evolved. Here, we provide early evidence. We combine 36 years of PM2.5 concentrations measured over ~8.6 million grid cells with geographic, economic, and demographic data from ~65,000 U.S. census tracts. We show that differences in PM2.5 between more and less polluted areas declined substantially between 1981 and 2016. However, the most polluted census tracts in 1981 remained the most polluted in 2016. The least polluted census tracts in 1981 remained the least polluted in 2016. The most exposed subpopulations in 1981 remained the most exposed in 2016. Overall, absolute disparities have fallen, but relative disparities persist.

中文翻译：

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美国PM2.5空气污染差异

更清洁的天空 近几十年来，美国本土的颗粒物空气污染已大大减少，但具体是在哪里取得的进展呢？科尔默等人。分析了 36 年的数据，发现细颗粒物浓度的空间分布在那个区间内基本保持不变（见马的观点）。尽管细颗粒物污染水平总体上有所下降，但那些在 1981 年污染最严重和最少的地区今天仍然如此。我们可能在污染控制方面取得了重大进展，但在解决社区之间的暴露差异方面却不太成功。科学，这个问题 p。575; 另见第 503 在过去的 40 年中，美国的颗粒物空气污染大幅下降，但相对模式仍然存在。任何特定时间的空气污染在不同地点的分布都是不均等的。直径小于 2.5 微米的细颗粒物 (PM2.5) 的平均浓度随着时间的推移而下降。但是，我们不知道 PM2.5 的空间分布是如何演变的。在这里，我们提供早期证据。我们将超过 860 万个网格单元测量的 36 年 PM2.5 浓度与来自约 65,000 个美国人口普查区的地理、经济和人口数据相结合。我们发现，1981 年至 2016 年间，污染程度高和污染程度低的地区 PM2.5 的差异大幅下降。然而，1981 年污染最严重的普查区在 2016 年仍然是污染最严重的地区。1981 年污染最轻的普查区在 2016 年仍然是污染最少. 1981 年暴露最多的亚群仍然是 2016 年暴露最多的亚群。