Trends in Exposure to Air Pollution from Power Plants

Featured in print Digest

Air pollution from electric power plants declined substantially between 2000 and 2018, and reductions in pollution exposure were broadly similar across various ethnic, income, and racial groups, Danae Hernandez-Cortes, Kyle C. Meng, and Paige E. Weber note in Decomposing Trends in US Air Pollution Disparities from Electricity (NBER Working Paper 30198). The study focuses on exposure to particulate matter that is released when burning fossil fuels. PM2.5 concentration measures the airborne level of particulates that are no more than 2.5 micrometers in diameter, or about 3 percent of the width of a human hair.

The researchers use Environmental Protection Agency data on almost 1,750 power plants to create a comprehensive record of production quantities and fuel inputs as well as air pollution emissions. Their dataset also includes smokestack characteristics such as stack height, temperature, velocity, and diameter, all of which are important for determining how air pollution travels. They use a pollution transport model to characterize pollution dispersal across space from each power plant, along with American Community Survey data to determine how the emissions from each plant affect pollution exposure for individuals in various ethnic, income, and racial groups.

Fuel substitution from coal to natural gas, coupled with local air pollution regulations, led to sharply lower particulate pollution from power generation in 2018 than in 2000.

Air pollution concentrations from electric power plants dropped by 89 percent, from 2.4 to 0.30 micrograms per cubic meter (μ/m3) per person, between 2000 and 2018. The national average ambient PM2.5 concentration level from all pollution sources fell during the same period by 39 percent, from 13.5 to 8.2 μ/m3. Power plants accounted for 18 percent of all ambient PM2.5 concentrations in 2000, but only 4 percent in 2018.

The reduction in exposure to air pollution associated with electric power generation was similar across racial, income, and ethnic groups: 90 percent for Blacks, 89 percent for Whites, and 86 percent for Hispanics. The dispersion across groups in exposure to PM2.5 concentration also dropped sharply. Over the 18 years the study considers, the gap in average PM2.5 exposure between Blacks and Whites declined from 0.75 to 0.036 μ/m3 per person — a 95 percent decline. The average White experienced a concentration 1.07 μ/m3 higher than the average Hispanic in 2000, but that disparity fell to 0.07 μ/m3by 2018.

The large disparities in exposure across different population subgroups at the start of the study period reflect the locations of electricity generation plants and where different population subgroups live. PM2.5concentrations from electric power plants were highest across southern states, which have larger Black populations. The next highest concentrations were in the Midwest, with a higher White population share. PM2.5 concentrations were lower in southwestern and western states, which have large Hispanic populations.

The researchers suggest that more than half of the particulate emission reductions from power plants during the period of study are attributable to a shift from coal to natural gas combustion for electricity generation. Most of the remainder was due to reduced emission intensity for a given fuel mix, often associated with air pollution policies such as the Clean Air Act.

— Brett M. Rhyne