Ozone

Ozone is an extremely reactive gas comprised of three atoms of oxygen. Ozone exists naturally in the Earth's upper atmosphere, the stratosphere, where it shields the Earth from the sun's harmful ultraviolet rays. However, ozone found close to the Earth's surface, called ground-level ozone, is a component of smog and a harmful pollutant.

Ground-level ozone is not emitted directly from a source, but forms through a series of complex chemical reactions between volatile organic compounds (VOCs) and nitrogen oxides (NOx) in the presence of sunlight. Sources of manmade VOCs and NOx include: 1) automobiles, trucks, and buses; 2) gasoline storage and transfer; 3) large combustion and industry sources such as utilities; 4) industrial use of solvents and degreasers; 5) consumer products such as paints and cleaners; and 6) off-road engines such as aircraft, locomotives, boats, construction equipment, and lawn and garden equipment. VOC's are also produced naturally by certain types of vegetation.

Natural ground level ozone occurs in low concentrations (less than .05 ppm) due to natural physical and chemical phenomena. Occasionally, unique meteorological conditions can result in natural levels between .05 and .10 ppm.

The highest ozone levels generally occur during summer afternoons when the high temperatures and strong sunlight promote photochemical reactions. Stagnant weather may cause smog to remain in an area for several days. The winds may also transport ozone many miles outside of the urban environment. For example, it is estimated that a significant portion of the ozone in the State of Maine is transported into the State from sources located outside the State. A much smaller amount of the ozone is naturally occurring background concentrations, part of which is also transported into the State. In addition, pollutants released into the atmosphere from sources within the State contribute to the formation of ozone. Because of long-range transport, local control of emissions by itself may not solve the ozone problem. An effective national program may be necessary to achieve national compliance.

Scientists have been studying the effects of ground-level ozone on human health for years. Their studies have found that ozone causes several types of health effects in the lungs. These health effects include irritation of the respiratory system, reduced lung function, aggravation of asthma, and inflammation and damage to the lining of the lungs. Symptoms associated with exposure to higher concentrations of ozone are shortness of breath, pain when inhaling deeply, wheezing, and coughing. Children, active adults, people with respiratory disease, and people with an unusual susceptibility to ozone are most sensitive to the effects of ozone.

Vegetation, such as white pine, soybeans, and alfalfa, are extremely sensitive to ozone. In addition, ozone is known to weaken materials, such as rubber and fabrics.

History of the various ozone standards (pdf file)

Ground-level ozone concentrations tend to be especially high during the summer months when the weather is hot and sunny and the ozone season runs from April 1st through September 30 th . However, ozone is no longer the only pollutant which is forecast. Maine DEP staff meteorologists now issue air quality forecasts every day of the year instead of only during the ozone season. They retrieve and review monitored pollution data and weather forecast information. Staff meteorologists then develop air quality forecasts for the following day. The forecasts use the color coded Air Quality Index categories. As required by Title 38, Chapter 4, § 584-F of Maine's statutes, whenever air quality is forecast to be above the 8-hour Ozone National Ambient Air Quality Standard, the Department sends out an Air Quality Alert press release. The Department also issues a press release for forecasts above the 24-hour PM 2.5 NAAQS. In addition to the press release, the forecast is sent to the National Weather Service. The forecast is made available to the public on a daily basis in the following ways:

•  24-hour toll free Air Quality Hotline: 1-800-223-1196

•  Internet /World Wide Web: http://www.maine.gov/dep/air/ozone/ or www.mainedep.com click on ‘Maine Air Quality Forecast'.

•  EPA's AIRNOW web site: http://cfpub.epa.gov/airnow/index.cfm?action=airnow.main

•  Enviroflash e-mail system: http://www.maine.gov/dep/air/ozone/enviroflash.htm (user defined alert levels)

•  Local Media

•  National Weather Service websites http://www.erh.noaa.gov/er/gyx/ and http://www.erh.noaa.gov/er/car/ (only for Air Quality Alert forecasts)

•  National Weather Service All Hazards Radio (only for Air Quality Alert forecasts)

Ozone was monitored by Maine DEP staff in the following areas of Maine during the 2007 ozone season using continuous monitoring equipment:

Coastal Sites: Kittery, Kennebunkport, Cape Elizabeth, Portland, Georgetown, Port Clyde, Castine, McFarland Hill in Acadia National Park, Cadillac Mountain in Acadia National Park and Jonesport.

Inland Sites: West Buxton , Durham , Gardiner, Holden and North Lovell.

Data from all of the state sites as well as two EPA operated sites in the towns of Ashland and Howland as part of the CASTNet program can be viewed on the air quality web site. Data from two Tribal sites operated in Perry and Old Town can also be viewed on the air quality web site. The sites operated in Kittery , Georgetown and Castine were terminated at the end of the 2007 season. Two new sites are expected to be in operation for the 2008 season to replace the Kittery and Georgetown sites.

 

Historical data as well as a number of trends in ozone concentrations and days of exceedances can be viewed in the latest annual air quality report .

 

 

 

 

 

 

 

 

 

 

 

 

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