Multi-hazard risk in socially vulnerable communities across the United States

Society's most vulnerable communities bear the burdens of a multitude of environmental shocks and stressors, which are increasingly likely to occur simultaneously or in quick succession. However, our understanding of where environmental risks accumulate across the United States and how determinants of multi-hazard risk vary within the country remains incomplete. This study offers a more comprehensive understanding of the national scope and underlying drivers of compounding environmental risks from five hazards (water shortage, air pollution, wildfire, flooding, and impaired water quality) in socially vulnerable communities in the contiguous United States. By pairing census tract-level Social Vulnerability Index data from the Centers for Disease Control with hazard exposure data, we find that over 11 percent of the population-37 million people-is at high risk from multiple hazards. We find that multi-hazard risk disproportionately accumulates in the most vulnerable communities and therefore constitutes an environmental injustice. Nationally, socioeconomically vulnerable populations (e.g., low-income households and those lacking health insurance) are inequitably exposed to multiple severe hazards. However, the specific combinations of demographic and environmental drivers of risk accumulation vary across regions. While the widespread nature of environmental risk accumulation indicates that reducing multi-hazard risk will likely require comprehensive rather than piecemeal approaches, results also highlight the need for context-specific interventions.