Inequality in Hazardous Air Pollutant Emissions and Concentrations Measured Over Los Angeles

In Los Angeles, air pollution disproportionately impacts
communities
of color and low-income residents. Routine city-wide measurements
of hazardous air pollutants (HAPs), of concern for health and contributing
to urban air pollution, are notably lacking. In this study, we use
the highest spatially resolved (∼2 km) measurements of emissions
and concentrations ever reported of HAPs while covering a whole megacity
and combine 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 (DACs) and census
tracts with low-income Hispanics and Asians. These groups share an
unequal burden from traffic-related emissions, with benzene, nitrogen
oxides (NOx), and carbon monoxide (CO)
concentrations up to 60% higher. However, in DACs 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
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.