Ozone Movies use real-time air monitoring data to show ozone air pollution levels throughout the region, by animating ozone concentrations as they build up on a map of the Bay Area.

What are the harmful health effects of ozone?

Ground-level ozone can cause several types of short-term health effects:

• Ozone can irritate the respiratory system. Ozone can cause coughing, irritate your throat, eyes, or nose, and/or cause headaches. These symptoms can last for a few hours after ozone exposure and may even become painful.
• Ozone can reduce lung function. "Lung function" refers to the amount of air that you draw in when you take a full breath and the speed at which you are able to blow it out. Ozone can make it more difficult for you to breathe as deeply and quickly as you normally would.
• Ozone can aggravate asthma. When ozone levels are high, more asthmatics have asthma attacks that require a doctor's attention or the use of additional medication. Ozone makes people more sensitive to allergens (such as dust mites, pets, and pollen) which are the most common triggers for asthma attacks.
• Ozone can inflame and damage the lining of the lung. Ozone's effect on the lining of the lung is comparable to the effect of sunburn on the skin. Ozone damages the cells that line the air spaces in the lung. Within a few days, the damaged cells are repaired, just as our skin recovers from a sunburn naturally.

Scientists suspect that ozone may have other effects on people's health, as well. Ozone may aggravate chronic lung diseases, such as emphysema and bronchitis. Also, studies in animals suggest that ozone may reduce the immune system's ability to fight off bacterial infections in the respiratory system.

Most of these effects are considered short-term because they eventually cease once ozone levels subside. However, there is concern that repeated short-term damage from ozone exposure may permanently injure the lung. For example, repeated ozone impacts on the developing lungs of children may lead to reduced lung function as adults.

Who is most at risk for experiencing the health effects of ozone?

• Children. Children are more sensitive to pollution than adults. Children typically spend more time and are more active outdoors. Pound for pound, they breathe more than adults. They breathe, drink, and eat to grow, not just to maintain themselves. Their air passages are also narrower than adults, so it takes less inflammation or irritation to obstruct a child's airways. Children are also more likely to have asthma or other respiratory illnesses.
• Adults who are active outdoors. Healthy adults of all ages who exercise or work vigorously outdoors are considered a "sensitive group" because they have a higher level of exposure to ozone than people who are less active outdoors. Ozone is typically a problem in the afternoon due to pollution generated in the morning.
• People with respiratory diseases, such as asthma. There is no evidence that ozone causes asthma or other chronic respiratory disease, but these diseases do make the lungs more vulnerable to the effects of ozone.
• People with unusual susceptibility to ozone. Scientists don't yet know why, but some healthy people are simply more sensitive to ozone than others.