New research reveals that fine particle air pollution from plants burning fossil fuels to make electricity was the cause of about 16,000 premature deaths in the United States during 2014.
In addition, the researchers found that while average exposures were higher for lower-income groups than they were for higher-income ones, racial disparity was more marked than income disparity.
Exposures were higher among black people and non-Latino white people than among other groups, such as Asian, Native American, or Latino people.
Emissions resulted in around seven premature deaths per 100,000 among black people and six per 100,000 among non-Latino white people. The average for other races was around four premature deaths per 100,000 people.
Another key finding was the large difference between the location of electricity generation and where the health consequences occurred.
"Some states are net exporters of health impacts, other[s] are net importers," conclude the researchers in a recent Environmental Science & Technology paper on the study.
In 36 states, power plant pollution from other states was responsible for more than half of the related premature deaths.
"Our data show that even if states take measures to change their own electricity production methods, what happens across state lines could dramatically affect their population," says senior study author Julian D. Marshall, a professor of civil and environmental engineering at the University of Washington (UW), in Seattle.
"These results can help local, state, or national governments make more informed decisions that will improve everyone's air quality and quality of life," he adds.
Particulate matter and health
Two types of particulate matter (PM) in air pollution give rise to health concerns: Coarse matter, or PM 10, includes particles under 10 micrometers (μm) in diameter, while fine matter, or PM 2.5, includes particles under 2.5 μm in diameter.
Scientists have been studying the relationship between particulate air pollution, health, and premature death for more than 25 years.
They have linked exposure to fine PM to strokes, heart attacks, lung cancer, and other health consequences.
An earlier study by Prof. Marshall and others estimated that, in the U.S., PM 2.5 pollution due to human activity was responsible for about 107,000 premature deaths in 2011, at a cost of $886 billion.
Electricity generation from fossil fuels is a large contributor to PM 2.5 air pollution, but scientists have known little about demographic variations in exposure.
Countrywide pollution map and model
So, for their new study, Prof. Marshall and colleagues estimated exposures to PM 2.5 from electricity generation, together with resulting health consequences. They did this "for each of the seven regional transmission organizations [...] for each U.S. state, by income, and by race."
"We looked at emissions from different types of power plants," says first study author Maninder P. S. Thind, "including coal, natural gas, diesel and oil power plants and modeled how the pollutants would travel, based on things like wind patterns or rain."
Thind, a doctoral student in civil and environmental engineering at UW, adds, "We also consider how emissions can react in the atmosphere to form fine particle air pollution."
From that data, they constructed a countrywide map of pollution levels. They then overlaid the map with census data to estimate where people lived and how the air pollution gave rise to health consequences.
By adding data on deaths from the National Center for Health Statistics, the team then estimated numbers of early deaths as a result of air pollution from power plants.
This was how they got the figure of 16,000 premature deaths due to power plant air pollution in 2014. They also found that 91% of these early deaths were due to fine particle air pollution from coal-fired electricity plants.
State by state variations
On a state by state basis, Pennsylvania had the highest number of premature deaths due to power plant emissions in 2014 – the team estimated this to be around 2,000.
The lowest numbers were in Idaho and Montana, with each having fewer than 10 premature deaths.
Kentucky had the largest disparity in emissions exposure by race, with black people being the most affected.
The research also highlights the contrast between the national average and regional variation.
For example, while Native Americans had the lowest exposure overall in 2014, this was the most exposed group in Kansas and Oklahoma.
"We've seen in our previous research that our society is more segregated by race than by income, and now it's showing up again with air pollution from electricity generation emissions."
Prof. Julian D. Marshall