Air quality statistics released by the National Park Service reveal that Sequoia National Park has the highest smog levels by a wide margin. The California park is home to the famous giant Sequoia redwood trees, which are now left to struggle to grow in the dense smog. According to the National Park Service, Sequoia National Park had 87 days of violations last year, and had ozone readings as high as 98 parts per billion, which the EPA deems “unhealthy for everyone.” Joshua Tree National Park, also located in California, came in second with 56 days of violations and ozone readings as high as 91 parts per billion.
In fact, the air quality at Sequoia National Park is so bad, job applicants are actually warned about it being an unhealthy workplace, and park workers are taught about the heart and lung damage the smog can cause. Some of the problems are caused by forest fires, but a lot of the pollution comes from the nearby major trucking highways that run through California’s San Joaquin Valley.
Great Smoky Mountains National Park in North Carolina came in third with 12 days of recorded violations, followed by California’s Yosemite National Park and Colorado’s Rocky Mountain National Park, both with 8 days of violations each. The highest ozone readings for the three parks ranged between 77 to 83 parts per billion, which is considered “unhealthy for sensitive groups.”