The Good, the Bad, the Ugly

Even though it’s made of only three little molecules of oxygen, ozone can be a pretty big topic. Newspaper headlines are confusing: One day ozone is good, the next day it’s bad.

In fact, both scenarios are true. Two types of ozone exist, stratospheric and tropospheric, and they differ greatly. Stratospheric ozone, which hovers between 10 and 30 miles above the Earth, is the naturally occurring “good” gas that protects the Earth from harmful ultraviolet (UV) rays. When chemicals like chlorofluorocarbons (CFCs) deplete this type of ozone, higher UV levels reach the Earth, facilitating skin cancer and other health threats.

Tropospheric ozone, on the other hand—the “bad” ozone—is a byproduct of fossil fuel combustion and a major component of smog. It exists in the lower atmosphere, up to 10 miles above ground. Tropospheric ozone can permanently damage people’s lungs and prohibit plants from producing and storing food.

Like oil and water, the two ozones don’t mix. Tropospheric ozone cannot travel into the stratosphere, so increasing the bad ozone will not help repair the good ozone layer. It’s confusing, agrees Kert Davies of Ozone Action. “People don’t know the chemistry,” he says. “They see an ozone alert [for ground-level ozone] and think the ozone layer has a hole in it today. The science education on it is really weak right now.”

Here’s a quick lesson: Take proper care of refrigeration and air conditioning equipment (which typically use ozone-depleting chemicals) to protect stratospheric ozone, and wear sunscreen to protect your skin from UV rays. To lessen the impact of tropospheric ozone, cut down on pollution by conserving energy and carpooling or using alternate transportation.