Environmentalists worry that climate change could cause problems with rising sea levels and crop failures in the coming decades, but one group of researchers has found it’s already causing health problems now.

Temperature increases linked to climate change are worsening air pollution in communities across the country right now contributing to a range of health problems from asthma to premature death, according to a new report from the American Lung Association.

The total number of Americans exposed to unhealthy air rose to nearly 134 million, according to the group’s 2018 State of the Air report. That represents a spike from 125 million in the previous year.

Ozone pollution — commonly known as smog — sits at the heart of America’s worsening air pollution problem. Warmer temperatures create conditions conducive to smog formation and lead air to stagnate, keeping dirty air from leaving a given area. The number of days with unsafe levels of ozone pollution increased significantly in 2014 – 2016, the timeframe evaluated in the report, at the same time as the planet experienced the hottest years on record.

“Climate change makes it harder to protect human health” the report says. “Too many cities suffered increased ozone from the increased temperature.”

The worsening ozone problem hit both the country’s largest population centers such as New York City and Los Angeles as well as smaller communities like Bakersfield and Fresno, according to the report.

The findings come as the federal government — led by Trump’s Environmental Protection Agency — has sought to slow programs aimed at addressing air pollution. Earlier this month, Trump signed an executive order asking the EPA to change federal air quality standards to reduce “unnecessary impediments to new manufacturing and business expansion essential for a growing economy.”

Federal law requires the EPA to administer the program in question, the National Ambient Air Quality Standards, using best available science without considering the cost to industry.

The Trump Administration’s efforts to stop global warming regulations have been even more aggressive. The EPA has stopped the Obama-era Clean Power Plan, which sought to reduce emissions of climate change-causing emissions, despite estimates that the program would cut air pollution and ultimately save 3,600 lives by 2030. And a range of other related regulations are on the chopping block, from vehicle emissions standards to a rule regulating methane emissions.

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Write to Justin Worland at justin.worland@time.com.