We’ve come a long way since the days when air pollution was a visibly deadly thing that could kill thousands of people upon exposure, as it did in The Great Smog of London in 1952, which The Crown so vividly depicted. But despite significant advances since the Clean Air Act of 1970, we’re not in the clear just yet. Air pollution—mostly from fossil fuel-burning power plants and vehicles—is still a health threat to everything with lungs.

While environmental advocates and the current EPA leaders are butting heads over climate change, how much we should be worried about the quality of our air right now? Are we basically smoking a pack a day when we venture into a city? What can individuals do to protect ourselves? Take a deep breath (gas mask optional) and read on to find out.

The Dangers of Dirty Air

Since 1970, the EPA reports that emissions of six common pollutants have gone down 70 percent nationwide. But the effects of the toxic gases and particulate matter that are still in our air can’t be ignored: The Lancet Commission on Pollution and Health just reported this fall that pollution was responsible for 9 million premature deaths in 2015.

There are two culprits that worry experts most. The first is ground-level ozone—not the kind high in the atmosphere protecting us from the sun, but the stuff that’s formed when burning fossil fuel emits oxides of nitrogen and volatile organic compounds (a.k.a. smog). This gas irritates the lungs, limiting their function, which can lead to asthma in some and potentially cause more adverse effects later in life.

The other is particulate matter, which refers to airborne particles that are smaller than 2.5 micrometers but still manage to carry with them contaminants, including organic compounds called polycyclic aromatic hydrocarbons (PAH). The damage PAH can inflict go beyond the lung issues and asthma aggravation you might expect, as Frederica Perera, professor of environmental health sciences at Columbia University’s Mailman School of Public Health and director of the Columbia Center for Children’s Environmental Health, explains.

“A combination of size and toxicity has conspired to make [PAH] particularly harmful in a number of ways,” she says. Because the gases and particles are so small, they bypass the filters in our noses and throats and go deep into the lungs, reaching the alveoli (the air sacs in the periphery of the lungs). “So they’re picked up in the blood and circulated systemically through the body. That is why there are a number of effects, not just respiratory effects, of breathing in air pollution.”

These and other pollutants cause oxidative damage (which harms our proteins, lipids, and DNA), affect autoimmune response, and cause inflammation, Perera says. That damage has been linked to cardiovascular issues such as heart disease, strokes, and atherosclerosis, as well as to neurodegenerative diseases. It’s not the equivalent of smoking two packs of cigarettes a day, Perera says, but it’s “on the continuum.”

“We have shown that when pregnant mothers are exposed to higher levels of PAH, their children are more likely to develop certain adverse conditions, like slightly reduced IQ and an increase in ADHD symptoms,” Perera says. “More recently, we and others have linked air pollution exposure of pregnant mothers to obesity in the children.”

There’s even a chance that exposure to pollutants now may lead to neurodegenerative problems such as Alzheimer’s decades later, Perera says, though she cautions against pointing to air pollution as the sole cause of all of these health issues.

“All of these diseases and disorders and problems have many factors involved,” she says. “These include genetics and nutritional factors and the immune status of the person.”

So what can you do about it?

If you’re really panicked about air quality, you could study the American Lung Association’s annual rankings of the “cleanest” cities in the country (in terms of ozone and particle pollution) and move accordingly. But there are a few easier steps:

Don’t exercise outside on bad air quality days.

You can check for these at airnow.gov, though Perera notes that indoor air quality might be bad on those days too, because buildings are more permeable than you think. “During exercise, one is inhaling more air and therefore more contaminants in the air per unit of body weight,” she says.

Exercise in parks instead of along busy streets.

Also avoid exercising in rush hour. According to an article published in the journal Breathe, this makes a significant difference in the emissions your active lungs will take in. (Just don’t stop exercising, because, you know, all the other benefits that outweigh the dangers.)

Keep your home air clean.

Use ventilation when cooking and avoid open grilling and even wood-burning fires (aw, man). “Any kind of combustion in the home should be minimized or eliminated,” Perera says.

Use a HEPA filter, especially if you live in a very polluted area.

“These are expensive and they’re expensive to run, but if you’re living near heavily trafficked roadways, for example, it might be valuable to use air filters,” Perera says.

Adopt some house plants.

Nature’s air filters can take care of carbon dioxide as well as other indoor pollutants such as formaldehyde and benzene.

Eat well.

“A diet rich in micronutrients that are found in fruits and vegetables can offset the oxidative damage in pollutants,” Perera says. Nutrients such as vitamin C help your cells build protection against the destructive molecules you may be inhaling regularly. In other words, those antioxidant-rich foods you eat in hopes of staving off colds and wrinkles can help protect you from cancer and cardiovascular disease.

Choose clean energy.

If your utility provider allows you to choose green energy, you can help make sure there’s a market for fossil fuel alternatives. Same goes for your vehicle choice too. Both smog and particulates are generated by a variety of sources, but a big source of both, especially in cities, are our cars.

Get active.

“The real answer to this problem is government action and actions by industry,” Perera says.

To help make this happen, start locally. Attend community board meetings and be in touch with your local government about the regulation of nearby businesses and to encourage the development of greener practices such as public transportation. You can also act on a bigger scale, writing to state reps in support of more laws to mitigate pollution in the country and around the globe.

“Advocating for clean air in one’s neighborhood, community—that can be very effective,” Perera says. “You can help yourself and you can help others.”

Sabrina Rojas Weiss lives in Brooklyn, surrounded by her fellow freelance writers and competitive stroller-pushers. Follow her on Twitter @shalapitcher.