U.S. utilities are moving away from coal-fired power plants in favor of natural gas and renewable energy sources. The move reduces greenhouse gas emissions. And according to new research from UC San Diego, the move can also save lives and increase crop yields.

Jennifer Burney, environmental scientist at UC San Diego, is the lead researcher.

"These pollutants, especially aerosols which are particles in the air, really cause a lot of damage. They hurt people. They change the way the sunlight is reaching the surface of the earth and that matters for crops," Burney said.

Listen to this story by Shalina Chatlani.

To conduct the study, she looked at satellite images, government health and agricultural data and mortality rates. Burney says she saw the same impacts from coal plant emissions everywhere she looked.

"If you're looking at just one spot and you see that a plant turns off and mortality rates drop off ... maybe there was something else going on here," she said. "But there are hundreds of locations where a plant has gone offline and so as you get more and more locations that are having the same changes in different locations, at different times, you can be more and more confident that it's not some other factor causing it."

Burney investigated hundreds of locations where American coal-fired power plants shut down between 2005 and 2016. Where plants shut down, the human mortality rate decreased and the crop yield increased.

"When any fossil fuel is burned it releases emissions into the atmosphere...particulate matter, compounds that contribute to the formation of ozone. These are very detrimental to human health and crop health," she said.

She estimates these shutdowns over a decade saved about 26,000 lives and 570 million bushels of crops. The study shows much of the negative impacts of coal come from its combustion products like carbon dioxide, alongside particulate matter like fly coal ash, which can have toxic materials like mercury and arsenic.

While many of these plants have gone offline in the United States, they've been transitioned into natural gas plants. The study says that's what has led to the overall decrease in emissions. In the same period between 2005 and 2016, over 600 natural gas units came online across the United States. According to the Union of Concerned Scientists, these plants emit 50 to 60 percent less carbon dioxide.

But while these plants lead to substantially lower emissions, climate advocates like Nicole Capretz, founder of the Climate Action Campaign non-profit, says natural gas plants still aren't the ideal alternative to coal plants, because they still cause pollution.



"Unfortunately, we are just replacing one dirty polluting fossil fuel with another dirty polluting fossil fuel," Capretz said. "And that is not the solution in order for us to be climate safe and climate ready ... we have to go straight to new technologies like solar, wind and batteries."

The Union of Concerned Scientists reports that natural gas still produces nitrogen oxide gases, which can cause respiratory problems. It also can still produces particulate matter and ozone that can lead to poor air quality.

California, which has a goal to reduce its greenhouse gas emissions by 40% from its 1990 levels by 2030, doesn't have any heavy polluting coal plants. But, the Los Angeles Times reports that about one-third of the state's power still comes from natural gas.

The environmental consulting firm Environmental Economics Inc., which has worked with California utility regulators, wrote in research last year that the state would still need to use upwards of 35,000 megawatts of gas capacity, which is not too far off from what the state already uses, according to the Los Angeles Times.



"The more expert evidence that exists to show why it's not acceptable to burn any fossil fuels, whether it's coal or natural gas ... the better. We applaud any and all research that comes forward," Capretz said on the UC San Diego study.

But, she adds, a shift from coal to natural gas isn't the takeaway. The takeaway is that burning fossil fuels generally has negative impacts on human health and the environment.

"We are still burning carbon and emitting it into the air and generating air pollution that has a direct negative impact on peoples' ability to breath," Capretz said.

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Shalina Chatlani

Science and Technology Reporter

I cover all things science and technology — from the biotech industry in San Diego to rooftop solar energy on new homes. I'm interested in covering the human side of science and technology, like barriers to entry for people of color or gender equity issues on biotech boards.

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