Emphysema is commonly known as a “smoker’s disease.” Yet a recent study shows that merely living in a smoggy place puts you at higher risk for this lung condition. Instead of working to protect millions of people from the harms of dirty air, the Environmental Protection Agency (EPA) has decided not to do anything about a serious ozone pollution problem in the eastern U.S.

Fortunately, a court tossed out the EPA’s plan after Earthjustice challenged it in court. That legal victory means EPA now is required to take action to protect public health.

Ozone, formed when emissions from cars, power plants, factories, and other sources react with sunlight, was already known to be hugely harmful to human health. When inhaled, the pollutant, which is also commonly referred to as “smog,” can cause a variety of negative health effects, from shortness of breath and coughing; to chronic illnesses such as chronic pulmonary disease and asthma; to premature death.

While ozone was already known to cause other types of lung damage, we now know that it is strongly linked to the development of emphysema, even in individuals who don’t smoke. A recent, comprehensive study involving over 7,000 participants in six U.S. metropolitan regions led researchers to conclude that long-term exposure to ambient air pollutants, especially ozone, was strongly associated with increased prevalence of emphysema. Even just a small increase in the ozone levels of one’s surroundings could result in health impacts equivalent to smoking a pack a day for 29 years.

Compounding the effects of this alarming finding, smog formation, like numerous other environmental harms, is likely exacerbated by climate change. Ozone forms when volatile organic compounds interact with nitrogen oxides in the presence of heat and sunlight. Therefore, climate change may increase the formation of smog, as elevated temperatures contribute to the conditions that give rise to it.

To help protect people from the harmful health impacts of ozone, part of the Clean Air Act obligates the EPA to ensure that air pollution from eastern states does not contribute to poor air quality in states that sit downwind. Numerous metropolitan areas — New York, Baltimore, Chicago, and Houston among them — continue to suffer from dirty air that does not meet the EPA’s standard and that endangers public health.

Significantly, Census data shows that the affected downwind portions of the country are disproportionately comprised of racial and ethnic minorities. And the effects of the health impacts caused by ozone are not evenly distributed: children and communities of color have been shown to be disproportionately exposed to air pollution. For instance, African American children are not only more likely to have asthma than non-Hispanic white children (13% vs. 8%), they are also 500% more likely to die as a result of asthma.

Though legally bound to address the problem, the EPA has thus far attempted to do nothing, asserting that smog-causing emissions are projected to decline as a result of existing programs, and thus, no further reductions are necessary. At the same time, the agency is actively seeking rollbacks of the programs that would guarantee such pollution reductions. This illogical and backwards course of inaction would have guaranteed that smog levels remain high. Given what is known about hazards of breathing ozone, this would harm the health of millions of people. Unwilling to stand for that, earlier this year environmental groups represented by Earthjustice filed suit to declare the agency’s inaction illegal. The Court agreed in a ruling issued last month, tossing out the EPA’s do-nothing rule and requiring the agency to take action to protect public health from the dangers of ozone pollution.

We now know that the harm of exposure to ambient air pollution is even more severe than previously thought — on par with impacts caused by regular smoking. The likelihood that ozone levels will increase at a faster rate as our climate warms only lends the problem more urgency. In short, the EPA cannot continue to do nothing: It needs to take action to reduce ozone pollution and save lives.