Ozone Fact Sheet

What You Should Know about Ozone and Ozone Health Advisories

Ozone is a toxic air pollutant that is a concern for people's health when levels in outdoor are high.

Ozone is the principal component of the mixture of air pollutants known as "smog" that is produced from the action of sunlight on air contaminants from automobile exhausts and other sources. Ozone levels are most likely to be elevated after noon through early evening on hot, sunny days. The United States Environmental Protection Agency (US EPA) last revised the National Ambient Air Quality Standard (NAAQS) for ozone in 2008. The standard is currently set at 0.075 parts per million (ppm) averaged over 8 hours.

Ozone Health Advisories are issued to alert the public when outdoor ozone levels are too high.

The New York State Departments of Health (DOH) and Environmental Conservation (DEC) alert the public when ozone concentrations in outdoor air are expected to be unhealthy for sensitive groups. An ozone health advisory is issued for the next day for a specific region when ozone concentrations at one or more monitoring stations in that region are predicted to be elevated. Each summer weekday morning, DEC staff review morning ozone monitoring data and weather conditions to determine if an ozone advisory is warranted for the next day or for the same day if monitoring data indicate the need for an advisory.

Ozone Health Advisories are more likely to be issued throughout the summer during periods of hot and sunny weather when outdoor ozone levels are highest.

In general, ozone levels are higher on hot, sunny summer days especially during episodes of stagnant air. Daily ozone levels can be influenced by local weather events, regional weather patterns and the presence of chemicals in the air that react to form ozone. Ozone advisories are issued based on predicted levels of ozone. There could be a few days each year when the monitoring data, meteorology and computer modeling fail to correctly predict the need for an advisory.

Breathing outdoor air with high ozone levels, even for a short period of time (hours or days), can affect health.

Short-term ozone exposure has been linked with adverse effects. Eye, nose and throat irritation, respiratory symptoms and decreases in lung function have occurred in healthy, exercising people breathing air containing elevated levels of ozone. Respiratory symptoms include shortness of breath, chest pain and coughing, and may occur in both adults and children. In community studies, days with high outdoor ozone levels tend to have increased hospitalizations for respiratory conditions and increased daily mortality rates. More limited evidence suggests that short-term exposure to elevated ozone levels might also aggravate heart symptoms in people with pre-existing heart disease or high blood pressure.

Breathing outdoor air with high ozone levels for long periods of time (years) may permanently affect health.

Animal studies suggest that long-term exposure to elevated ozone levels may be associated with permanent changes in airway structure and reductions in lung function. Current information about permanent health effects from long-term exposure in humans is inconclusive. Some human studies reported evidence of permanently reduced lung function development associated with long-term childhood exposure to elevated ozone levels, while other have not. An increased risk of developing asthma was found among children who likely experienced long-term elevated ozone exposure because they participated in athletic programs in areas with high average ozone levels.

When an Ozone Health Advisory is issued, people should consider limiting their time outdoors doing strenuous physical activities. This is especially true for young children, the elderly and for people with respiratory or heart problems.

When ozone levels are elevated, the New York State Department of Health recommends limiting strenuous outdoor physical activity, especially during afternoon and evening hours, to reduce the risk of adverse effects. People who may be especially sensitive to the effects of ozone exposure include young children, the elderly, those who exercise or are involved in strenuous outdoor work, and those with pre-existing respiratory or heart problems. Those with symptoms may want to see their personal physician.

Additional Links

For more information call:

  • NYS Department of Health at 518-402-7530 or 1-800-458-1158
  • NYS Department of Environmental Conservation at 1-800-535-1345
  • Or visit DEC's Ozone website