The Environmental Protection Agency (EPA) today finalized a rule that requires upwind polluters to reduce their smog-forming emissions, which have been harming downwind states’ air quality.

Advocates pushed EPA to finalize its Good Neighbor Rule, which requires power plants and other industrial sources in 23 upwind states to reduce their smog-causing emissions. Smog, or ground-level ozone, is an intense air pollutant that worsens our breathing and increases our risks for lung and heart disease. But air pollution does not stay in one place, it moves between states. So, for example, industry and power plants in Texas emit air pollution that contributes to dangerous smog levels as far away as Illinois.

“For years, states have failed to live up to their ‘Good Neighbor’ obligations,” said Kathleen Riley, Earthjustice attorney. “We are pleased that EPA has responded to calls from overburdened communities to require pollution reductions from industrial sources in addition to power plants, and to ensure the largest coal-fired power plants run their pollution controls every day of the ozone season. Communities across the country have too long suffered from harmful smog pollution originating in upwind states.”

Smog is a persistent problem. More than 127 million people live in parts of the country that suffer from harmful smog levels. The Good Neighbor Rule will prevent premature deaths, save on healthcare costs and nudge power plants and heavy industry to finally clean up their act by installing and operating workable technology that reduces their harmful air pollution.

The Good Neighbor Rule is one step EPA can take to protect people from the adverse health impacts that air pollution has on people. But smog is just one of two of the most harmful and widespread types of air pollution harming people. The other is soot, or particulate matter. Soot is created largely by fossil fuel combustion happening in electricity generation, manufacturing, transportation, and even agriculture.

Recent studies show the national standard for particulate matter, like the ozone standard, is far too weak to protect people from adverse health impacts such as death, lung cancer, reproductive harm, and cardiovascular disease. EPA recently proposed a new standard for soot but it’s not nearly as strong as scientists and doctors say it needs to be. EPA must pass stronger soot and smog regulations that would save tens of thousands of lives.