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About Ozone (O3)

Ground Level Ozone Pollution

Ozone over New York City
NYC - February 2005.

Ground level ozone is not emitted directly into the air, but is created in the air itself by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC). Ozone forms on hot sunny days when pollution from cars, power plants, consumer products and other sources react with sunlight. Ozone is most likely to reach harmful levels on urban areas on hot, sunny days. Ozone, and the chemicals that form ozone can be blown long distances, so even areas outside of cities can experience high levels of ozone.

Health Effects of Ground Level Ozone

Ozone in the air we breathe can harm our health. People most at risk from breathing air containing ozone include people with asthma, children, older adults, and people who are active outdoors, especially outdoor workers. Breathing ozone can trigger a variety of health problems including:

  • Eye irritation
  • Chest pain
  • Coughing, shortness of breath and decreased lung function
  • Increased susceptibility to respiratory infections
  • Increased likelihood of asthma attacks
  • Inflammation of the lungs
  • Ozone can worsen bronchitis, emphysema, and asthma, leading to increased medical care.

New York State Warns of High Ozone Levels

Public health officials caution against strenuous outdoor activity when ozone levels are high. To help people decide when to curtail activity, DEC forecasts ozone pollution and, in cooperation with the NYS Department of Health, posts warnings if dangerous conditions are expected to occur. These warnings are also aired through the media and are available online from the Air Quality Forecast webpage or toll-free New York State Air Quality Hotline: 1-800-535-1345.

Environmental Effects of Ground Level Ozone

  • Damage to leaves, trees and other plants during the growing season. Ozone damages plants by entering leaf openings called stomata and oxidizing (burning) plant tissue during respiration.
  • Plants, trees, and other vegetation can suffer from a slower growth rate when they are exposed to high levels of ozone.
  • Sensitive plants are at greater risk for disease, insect damage and other environmental effects.
  • The damage to individual plants can have a negative impact on ecosystems by causing a loss of species diversity.
  • Some plants, such as the Cotton Plant or the Tulip Poplar cab show visible marks on their leaves when they are ozone is present under certain conditions.

How to Reduce the Formation of Ground Level Ozone

Routine activities at home, such as mowing your lawn or turning on your air conditioner, create air pollution. Some ways to reduce ozone pollution include:

Plant showing damage caused by ground-level ozone
Cotton plant showing damage caused by ground-level ozone.
Courtesy of USDA-ARS, Fitzgerald Booker
  • Choose a cleaner commute - car pool, public transportation, bike or walk when possible.
  • Combine errands and avoid extended idling.
  • Use environmentally safe paints and cleaning products whenever possible.
  • Avoid gasoline and chemical spills around the home.
  • Avoid using polluting chemicals during poor air quality days.
  • Conserve electricity. Consider setting your thermostat a little higher in the summer and lower in winter.

More tips for reducing air pollution can be found on the Clean Air Starts at Home page.

Monitoring Ground Level Ozone

The primary purpose for maintaining ground level ozone sites is to measure, on a continuous basis, the concentration of various pollutants, including ozone, in the ambient (outdoor) air. DEC's sites are maintained through the ozone monitoring season from March through October.

More information about specific sites measuring ozone can be found on the DECinfo Locator map. DECinfo Locator is an interactive map that lets you access DEC documents and public data about the environmental quality of specific sites in New York State, as well as outdoor recreation information. Air monitoring sites can be found under DEC Information Layers > Environmental Monitoring with the icon to the left. As a note: you may need to zoom in for the icons to be visible.