Mike Bergin first saw particles on solar panels on a rooftop of a building at Indian Institute of Technology at Gandhinagar.

According to a new study, air pollution may have yet another harmful effect—reduction of solar energy production.

Researchers from Duke, the Indian Institute of Technology at Gandhinagar and the University of Wisconsin at Madison performed the research, which appeared last month in Environmental Science & Technology Letters. The investigators—including Mike Bergin, professor in the Department of Civil and Environmental Engineering, and Drew Shindell, professor of climate sciences at the Nicholas School of the Environment—found that solar energy production was reduced by about 17 to 25 percent in India, China and the Arabian Peninsula due to particulates in the air.

“The main reason we care is that [pollution] kills people because it's toxic to breathe, but it also damages our food supply—and now, we find yet another thing,” Shindell said. “If you really did the economic analysis of these things, you would find that this is yet another reason why the apparently cheap, but very dirty fossil fuels are actually not so cheap.”

Bergin said that on a trip to India, his colleagues at IIT-Gandhinagar took him up to the roof to showcase their solar panels. He noticed that they were “totally coated” with dust particles and became interested in how particles on the panels and in the air affected solar energy production.

Using Shindell’s global climate model, which quantifies the effects of air pollution relative to the solar panel's baseline, Bergin noted that the researchers were able to predict “the amount of sunlight getting to the surface and how much of it was being blocked because of air pollution” around the world. The models were also compared to actual measurements in the field, which provided a similar picture.

Shindell said that while China’s large solar productivity reduction was due to pollution from human activity, the reduction in India and the Arabian Peninsula could be attributed to additional factors—arid climate and wind-blown dust from deserts.

“What [the Arabian Peninsula needs to do] is clean the panels fairly often, maybe more often than other places or after their big dust storms because there's so much material blowing around in the air there,” Shindell said.

As for the United States, Shindell described its air pollution reduction over the past 30 years as "one of our environmental success stories." He noted, however, that domestic air pollution still contributes to a 10 percent loss in solar power productivity.

The research ultimately verified one hypothesis for Shindell and Bergin—reducing air pollution benefits more than what meets the eye.

“There's a lot of really awesome benefits of decreasing these [human-generated] pollutants,” Bergin said. “If you decrease these particulates, you would get less carbon dioxide, less people getting sick from breathing these things in. But also now, we come to find that you would also have a dramatic increase in solar energy production. It's kind of something that people had not foreseen, but I think this is just another great benefit of reducing emissions of air pollutants.”