Inequality in hazardous volatile organic compound (VOC) emissions and concentrations measured over Los Angeles

In the United States, PM_2.5 and NO_x pollution disproportionately burden communities of color and of lower income. However, such information is lacking when it comes to hazardous air pollutants (HAPs) like toxic volatile organic compounds, for which city-wide measurements are more challenging and thus are not available in routine observations.

In this study, we use the highest spatially resolved (~2 km) airborne measurements of emissions and concentrations ever reported of HAPs while covering a whole megacity, and combine these observations with US Census information. We observe higher concentrations and emissions of 17 measured HAPs – such as benzene, naphthalene, and p-chlorobenzotrifluoride (PCBTF) – in California-designated Disadvantaged Communities and census tracts with low-income Hispanics and Asians. While concentrations were on average 32 ± 5% higher for low-income Hispanics compared to high-income non-Hispanic whites, emissions were even 107 ± 21% higher - indicating the proximity of low-income Hispanics to localized emission sources. Low-income Hispanics and Asians share an unequal burden from traffic-related emissions, with benzene, nitrogen oxides (NO_x ), and carbon monoxide (CO) concentrations up to 60% higher. However, in Disadvantaged Communities and census tracts with large Hispanic populations (>50%), we observe toluene-to-benzene emission ratios above 3, pointing to inequalities in other HAPs primarily caused by non-traffic emission sources such as industry and solvents. In these communities, regulatory inventories also significantly underestimate the observed emissions. We find that efforts to address HAP inequalities and environmental justice concerns in Los Angeles will need to consider contributions from volatile chemical products, which represent a growing source of emissions driving inequalities in impacted communities.