Toxic chemicals pose significant threats to ecosystems, climate change, and human health. Unfortunately, pollution inequality is pervasive in the United States, with a disproportionate exposure of racial/ethnic minorities and low-socioeconomic groups to toxic releases. This inequality is especially pronounced in Houston, Texas. Moreover, income inequality has widened over decades, and the distribution of toxic releases has changed over time in the USA.

To better understand the problem of pollution inequality, it is necessary to investigate the embodied toxic release in final demand by states and income groups. Notably, pollution inequality is non-uniform across regions and over time in the USA. The relationship between socioeconomic development and toxic risk necessitates analysis to comprehend the resultant health outcomes at different spatial scales and locations. Further, identifying the spatial heterogeneity of the association between environmental hazards and socioeconomic indicators is critical for addressing environmental inequality. Investigating the spatiotemporal heterogeneity of the impact of racial disparities and socioeconomic development on toxic risk can reveal disparities between regions and trends in pollution inequality.

This study employs an extended U.S. multi-regional input-output (MRIO) model with toxic chemical release data to analyze the inter-regional transfer of embodied toxic release between states and their unequal distribution between income groups from a consumption-based perspective. Additionally, this study analyzes the spatial non-stationarity in the associations between toxic chemical hazard risk and community characteristics of census block groups in Texas, USA, for 2017 using a multiscale geographically weighted regression (MGWR). Further, this study uses Houston, a city with a history of segregation and discrimination and a diverse racial/ethnic makeup, as an example to analyze the spatiotemporal heterogeneity of the impact of racial disparities and socioeconomic development on toxic risk using geographical and temporal weighted regression (GTWR) models. The study's outcomes are instrumental in determining whether pollution inequality has improved or worsened. Results indicate that non-metallic and metallic products manufacturing sectors are crucial for interregional flows of embodied toxic release from the Great Lake Region to Southeast, Mid-Atlantic, and Northeast regions, and are the most important sectors for most states from the consumption-based perspective. The findings also highlight the significance of identifying the spatial patterns of the association between toxic chemical hazard risks and community characteristics at the census block group level to address environmental inequality.