These 7 states have the worst air pollution in the U.S.

Air pollution takes a toll on your lungs and can be bad for your brain, increasing psychological stress and cognitive decline in adults.

A 2019 Proceedings of the National Academy of Sciences study even found that the annual toll of Americans who have died from air pollution — some 100,000 — is almost equal to the number of people in the U.S. killed in car crashes every year.

Put simply, you should avoid spending lots of time in highly polluted places. That's bad news for a good handful of states, according to a new U.S. News and World Report analysis, which ranked all 50 U.S. states according to how polluted they are and the risk that pollution poses to people's health.

The ranking is based on 2019 data from the U.S. Environmental Protection Agency, which measured the total toxic chemical pollution generated in each state and the risks of long-term, chronic health effects — from cancer to birth defects — posed to each state's population per capita.

Those measurements accounted for air and water emissions from manufacturing, electric power generation, mining and hazardous waste treatment, according to the U.S. News and World Report. They didn't include pollution from transportation, agriculture or small facilities like auto body shops or dry cleaners.

Here are the ranking's seven worst states, starting at the bottom:

Louisiana coming in dead last is no surprise: A 2020 analysis by the Environmental Integrity Project found that Louisiana is home to four of the top ten "super polluter" chemical plants in the U.S. A 2019 ProPublica investigation also found that the number of plants in Louisiana with high emissions has increased since the 1980s, despite the overall number decreasing nationally.

At least 85 cancer cases per year in the state are due to exposure to high levels of air pollution, according to a January 2022 study from Tulane University.

Nevada's status as the second-most polluted state is also seemingly well deserved: In 2021, the American Lung Association also ranked the state's air quality among "the unhealthiest for the most harmful and widespread types of air pollution." That same year, the cities of Las Vegas and Reno were listed on the organization's top 25 cities most polluted by short-term particles, or harmful particles in the air that are dangerous to breathe.

Oregon's appearance on the list may be somewhat surprising: The state is home to 11 national forests, a national grassland and even 21 national wildlife refuges. Oregon's website notes that cars and trucks are the state's largest source of air pollution, and frequent wildfires only worsen the state's poor air quality.

A handful of Oregon cities rank among the country's most polluted, according to the ALA.

At the other end of the spectrum, Vermont took home the U.S. News and World Report's top spot as the country's least polluted state. Vermont's cities are among the cleanest by air quality in the country, and have particularly low levels of the most harmful types of air pollution, the ALA says.

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