SEQUOIA NATIONAL PARK, California — The California forest that is home to the biggest and oldest living things on earth, the giant Sequoia redwoods, also suffers a dubious distinction. It has the worst air pollution of any national park in the U.S.

“Ozone levels here are comparable to urban settings such as LA,” said Emily Schrepf of the nonprofit advocacy group the National Park Conservation Association. “It’s just not right.”

Signs in visitor centers warn guests when it’s not safe to hike. The government employment website warns job applicants that the workplace is unhealthy. And park workers are briefed every year on the lung and heart damage the pollution can cause.

Although weakened trees are more susceptible to drought and pests, the long-term impact on the pines and on the giant redwoods that have been around for 3,000 years and more is unclear.

To read the full article, click here.