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At Mammoth Cave, Studying the Effect of Ozone on Plants


High ozone levels aren’t healthy for people, especially the very young, elderly or sick. But the pollution is bad for plants, too, and researchers at Mammoth Cave National Parkare trying to determine its effects on the park’s flora.Ozone is created when pollution cooks in the sun. There’s a federal standard for ozone pollution—and the Environmental Protection Agency announced this week that it will become more stringent soon—but that’s based on human exposure.Bobby Carson, chief of science and resources management at Mammoth Cave, said the National Park Service has been measuring ozone damage to plants annually, and has found many are sensitive to high ozone concentrations.“What we’ve been seeing is obviously these plants, trees and vegetation are out there in the resource 24/7, so they’re getting a lot more exposure than you do,” he said.The plants uptake ozone when they exchange gas with the environment. And Carson said that’s apparent on many plants. You can see spotting, the plants may lose their leaves earlier than normal. Overall, the ozone weakens the plants and makes them more susceptible to insects and disease.And this in Mammoth Cave National Park, which is Kentucky’s onlyClass 1 airshed.This means that area receives the highest protection under the Clean Air Act, and hypothetically has the cleanest air in Kentucky.Carson said his focus is on protecting the resources of the park, and ozone levels need to be brought down to ensure the plants are protected.“We want to get to a situation in the ambient environment where we don’t have that injury occurring, which means we still need to bring ozone levels down to lower levels so we don’t have that happening,” he said.The species most sensitive to high ozone levels tend to be native species, while many invasive species have a higher tolerance, he said.The current ozone standard is 75 parts per billion, both as a primary standard (for human health) and a secondary standard (to prevent damage to plants, crops, animals and buildings). Today, the Environmental Protection Agency proposed changing the standard to a stricter 65 to 70 parts per billion, again, both for primary and secondary exposure.

Erica Peterson is WFPL's Director of News and Programming.