Effects of Ground-level Ozone

Human Health Effects

Image of a healthy lung airway Image of an inflamed lung airway
Ozone can inflame the lung’s lining. These photos show a healthy lung air way (left) and an inflamed lung air way (right). Photos courtesy of EPA.
Breathing ground-level ozone can trigger a variety of health problems including chest pain, coughing, throat irritation, and congestion. It can worsen bronchitis, emphysema, and asthma. Ozone also can reduce lung function and inflame the lining of the lungs. Repeated exposure may permanently scar lung tissue.

Healthy people also experience difficulty breathing when exposed to ozone pollution. Because ozone forms in hot weather, anyone who spends time outdoors in the summer may be affected, particularly children, outdoor workers and people exercising. Some people who don't fall into any of these categories may also find themselves sensitive to ozone.

For detailed information about how ozone affects human health, go to EPA's "Health Effects of Ozone in the General Population" web page.

Environmental Effects

Ozone can reduce lung function, making it more difficult to breathe deeply and quickly. Those with lung diseases, children, outdoor workers, and those who exercise outdoors should reduce activity levels or stay indoors when ozone levels are elevated.

Ozone damages vegetation and ecosystems by inhibiting the ability of plants to open the microscopic pores on their leaves to breathe. It interferes with the photosynthesis process by reducing the amount of carbon dioxide the plants can process and release as oxygen.

Elevated levels of ozone leads to reduced agricultural crop and commercial forest yields, reduced growth and survivability of tree seedlings, and increased susceptibility to diseases, pests and other stresses such as harsh weather.

Image depicting ozone damage in a pumkin leaf

Signs of ozone damage include flecking, stippling, bronzing and reddening on plant leaves. Photo courtesy of USDA

Yield Loss Caused by Ozone

Dicot species, such a soybean, cotton and peanut, are more sensitive to yield loss caused by ozone than monocot species such as sorghum, field corn and winter wheat. The USDA provides additional information on the effects of ozone air pollution on plants.

Chart depicted yield response of various crops due to seasonal ozone levels
Heagle, AS. 1989. Ozone and crop yield. Annual Review of Phytopathology 27:397-423.

EPA Health Standard and Iowa's Ozone

The chart below demonstrates Iowa’s level of ozone pollution compared to the EPA’s health standard for the past decade. The health standard became more stringent as science and health experts learned that humans and the environment are impacted by pollution to a greater extent than previously believed. The EPA will lower the standard once again by July 31, 2011. The new standard is expected to be between 60 and 70 parts per billion. 

Chart depicting ozone design values at various locations in Iowa over the past few years

The Design Value is a calculation which characterize a three-year pollution level.

Regulated industries and businesses have made serious efforts to reduce or capture ozone precursors. Significant reductions in air emissions through cleaner fuels and vehicles occurs as older on-road and off-road engines are replaced or upgraded. To clean the air to a healthier level, everyone’s efforts to reduce fuel combustion and energy use are needed.

More information about Iowa’s ozone monitoring program is available here.