Nitrogen dioxide, a precursor to ground-level ozone and particulate matter, is produced mainly by vehicles and power plants. In Houston, petrochemical refineries and industrial activities also emit this pollutant, which has been linked to respiratory problems. The researchers used the NASA airborne spectrometer data to examine differences in population-weighted nitrogen dioxide levels for different census tracts. The areas where the pollutant was highest were where more low-income, non-white and Hispanic people lived. In contrast, where the pollutant was lowest, high-income, white people tended to live there. Most of the disparities could be explained by proximity of the neighborhoods to industrial sources and heavy-duty diesel vehicles.
— source American Chemical Society | Aug 5, 2020