Ground-level ozone is harmful to human health and the environment.

In the earth's lower atmosphere, ground-level ozone is considered "bad."

Ground-level ozone, however, is a health hazard because people breathe it.

Ground-level ozone is another big contributor to the smog problem.

They chose to look at ground-level ozone because it is one of the most difficult air pollution problems to solve.

Greatly reducing the amount of ground-level ozone, they contribute to air quality.

Most of the local regulations are designed to cut those emissions in half, meaning that ground-level ozone will be reduced by only about 1.5 percent.

High concentrations of ground-level ozone seriously affect human, animal and plant health.

You also protect your health by avoiding ground-level ozone during the warmest part of the day.

One tightened the standards for ground-level ozone, a major contributor to smog.