County-Level Artificial Light at Night (ALAN) in the Contiguous U.S. (2012-2019): Spatial Variations, Temporal Trends and Environmental Justice Analyses

Abstract

Abstract Artificial light at night (ALAN) is a growing environmental exposure with economic, ecological and public health implications. Moreover, previous studies suggested a higher burden of light pollution and related adverse effects in disadvantaged communities. It is critical to characterize the geographic distribution and temporal trend of ALAN and identify associated demographic and socioeconomic factors at the population level to lay the foundation for environmental and public health monitoring and policy making. We used satellite data from the Black Marble suite to characterize ALAN in all counties in contiguous US and reported considerable variations in ALAN spatiotemporal patterns between 2012 and 2019. As expected, ALAN levels were generally higher in metropolitan and coastal areas; however, several rural counties in Texas experienced remarkable increase in ALAN since 2012, while population exposure to ALAN also increased substantially in many metropolitan areas. Importantly, we found that during this period, although the overall ALAN levels in the US declined modestly, the temporal trend of ALAN varied across areas with different racial/ethnic compositions: counties with a higher percentage of racial/ethnic minority groups, particularly Hispanic populations, exhibited significantly less decline. As a result, the disparities in ALAN across racial/ethnic groups exacerbated between 2012 and 2019. In conclusion, our study documented variations in ALAN spatiotemporal patterns across America and identified multiple population correlates of ALAN patterns that warrant future investigations.