Unhealthy air pollution generally brings to mind coal-fired plants spewing black soot from a smokestack. But that image may quickly be becoming outdated. A study published on Wednesday in Environmental Research Letters found that using natural gas and biomass in sources like buildings and industrial boilers actually caused more deaths in 19 states as a result of air pollution than burning coal.
To conduct the study, researchers looked at the health impacts from fine particulate matter air pollution, or PM2.5, tied to burning different fuels. PM2.5 can cause a whole host of health problems, including numerous cardiovascular and respiratory diseases. Different forms of PM2.5 can include pollutants like sulfur dioxide, nitrogen oxides, and volatile organic compounds, and can come from a variety of sources, including burning coal, gas, and wood.
The particles that cause these kinds of health problems “are wide enough that you can fit about 20 of them across a human hair,” said Jonathan Buonocore, the lead author of the study and a research scientist at the Harvard TH Chan School of Public Health. PM2.5 particles can travel from inhalation into the bloodstream, and he said “every single system is in the body” can be harmed.
The study found that PM2.5 exposure caused between 47,000 and 69,000 premature deaths nationwide in 2017, the most recent year in the federal pollution dataset they used. By taking pollution data from federal sources and state databases and running those numbers through three separate computer models, researchers deduced that more than 70% of those deaths—between 33,000 and 53,000—were due to fuel sources other than coal, among them natural gas, wood, and biomass. That percentage is a big jump from 2008 data, which shows that emissions from coal-fired power plants were the dominant source of deadly PM 2.5. What’s more, PM2.5 emissions from natural gas sources caused more premature deaths than coal did in 19 states plus the District of Columbia. California, Colorado, Massachusetts, Mississippi, New York, and Oregon are among the states, pointing the geographic diversity.
The research, ironically, is actually a result of a bit of good news. Deaths from coal pollution are so low because we’ve been rapidly moving away from using coal to fuel electricity generation, partly because of national and state policies, but mostly because of economics as renewables and natural gas have become cheaper and cheaper. Several of the states in the study have only one or two coal-fired power plants remaining in their borders. (Massachusetts, New York, and Oregon all closed their last plants in the past couple of years.) In 2008, PM 2.5 pollution from electricity generation—mostly coal-fired sources—alone was responsible for 59,000 and 66,000 premature deaths around the country; in 2017, that number was down to just 10,000 to 12,000.
“All other things being equal, if coal plants remained online, there would be higher impacts from coal,” said Buonocore. “However, if we had switched over to renewables more aggressively, there would be even fewer deaths due to electricity generation.”
Electricity generation isn’t the only way we use fuels and generate PM2.5, though. Heating residential and commercial buildings, cooking, powering industrial boilers, waste disposal, and other kinds of industry all come with deadly emissions. The findings show these activities continue to take a toll on public health.
The study comes amid a growing movement across the U.S. to ban natural gas hookups in new buildings. While most of these fights have been motivated by concern over planet-heating methane emissions, the air pollution models make it clear that there could also be huge health benefits for swapping gas use in buildings for cleaner energy sources. What’s more, the total health impacts of using gas and biomass in buildings could actually be an undercount because they don’t take a look at what we’re actually exposed to inside.
“The study shows that buildings are the leading sources of outdoor air pollution,” said Buonocore, but it “doesn’t include indoor impacts from the air pollution I get exposed to from, say, my stove.”
Retiring the bulk of the nation’s coal-fired power plants was a big win for reducing overall carbon emissions; figuring out how to eliminate carbon emissions from the various other sectors that contribute to climate change may be more of an uphill slog marked with smaller and smaller victories. The study demonstrates that curbing air pollution from various fuel sources may work in the same way.
“Switching out one combustion fuel for another is not a pathway that gets you to a healthy energy system,” said Buonocore. “From a regulatory standpoint, this shows that there’s been a shift in health impacts being from large power plants and large energy sources to smaller, more numerous, but more distributed sources. In order to continue to reduce impacts from air pollution, the strategy for how we regulate air pollution has to change.”