Science Weekly: Effects of Ozone Pollution on Plants


Ozone is still a problem–but not for the reason you’re thinking of.

At the National Center for Atmospheric Research, scientist Danica Lombardozzi studies how ozone pollution is detrimental to living organisms.

But wait–isn’t ozone good for the earth?

“Ozone can be a really confusing topic,” Lombardozzi admits.

High in the atmosphere, where we don’t breathe it, ozone provides essential protection from the sun’s harmful rays. We would not have life on earth as we know it without the ozone layer.

Yet that same exact chemical compound is toxic to us in the air that we breathe.

According to Lombardozzi: “If we had to interact with the stratosphere, we wouldn’t be alive.”

Ozone can be found at 500 parts per billion high in the atmosphere, yet where humans breathe, it is closer to 70 parts per billion.

“We would not be in good shape,” Lombardozzi said, if we had that much ozone at ground level.

Visible effects of excessive ozone causes black spots on plant leaves, known as stipples. And certain plants are more sensitive to ozone. These two elements are combined in Lombardozzi’s research to study the effects of different variables, such as time, geographic location and altitude, on specific plant species.

Stipples on a plant leaf.

These stipples on plants, predisposed to showing signs of ozone damage, act as canaries in the coal mine–planet earth. Ozone at ground level is bad for humans and plants alike, and many people don’t realize that. It’s one of the primary components of smog and one of the primary pollutants that the EPA regulates.

Colorado has high ozone concentrations compared with other areas of the U.S., in which ozone levels vary regionally. With the extraction of natural gas and an increase in fracking, more methane is released into the atmosphere, and that can create more ozone. Methane, along with reactive nitrogen and volatile organic compounds, are key components in the creation of ozone when hit by sunlight.

Ozone is natural at ground level, but at concentrations of about 10 parts per billion–and not the now average 70 parts per billion. Colorado and the Front Range have even been out of compliance with the EPA for the past 7 or 8 years. The state is predisposed to more ozone, with a higher than average number of sunny days during the year.

Pollution from ozone affects crop yields and can contribute to global warming because when a plant is damaged, it is not as productive and doesn’t take up as much carbon.

“Not only is it toxic,” Lombardozzi said, but ozone pollution”can also lead to climate change.”

It’s even in pristine places, such as Rocky Mountain National Park, where visible signs of damage on plants are present.

In the above slide, a variety of potato plant that is sensitive to ozone goes from showing initial stipples in June 2014 to becoming a struggling organism in October.

Plants like this have what is called a “threshold response,” where once they get ozone damage, they change for the worse quite quickly. These results and this project, Lombardozzi hopes, will allow “people to look at plants and visualize an invisible pollutant.”

Because if those spots on that plant are from ozone, she points out, the next questions is: “what do my lungs look like?”

Some countries have started regulating ozone, and it is expected to stay at the same levels it is today or go down worldwide in time. But until this type of research is widely known, it’s not guaranteed ozone pollution will be taken seriously.

With her work, Lombardozzi hopes “that some of these stories will help us, so it’s not getting worse.”

Learn more about Lambardozzi’s work here