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Historical Ground-level Ozone Exceedances in New England
In July 1997, EPA revised the former 1-hour ozone standard and replaced it with a more protective 8-hour standard at a level of 0.08 parts per million (ppm). The 1997 0.08 ppm, 8-hour ozone standard is met at an air quality monitor when the 3-year average of the annual fourth-highest daily maximum 8-hour average ozone concentration is less than or equal to 0.08 ppm (that is, 0.084 due to rounding).
In March 2008, EPA again revised the ozone standard. The 2008 ozone standard is set at a level of 0.075 ppm averaged over an 8-hour period. This standard is met at an air quality monitor when the 3-year average of the annual fourth-highest daily maximum 8-hour average ozone concentration is less than or equal to 0.075 ppm
Areas in New England that are not meeting the 1997 8-hour ozone standard are shown in this map. EPA will designate areas not meeting the 2008 ozone standard by March 2010.
The historical 8-hour ozone data available here for the New England states includes:
- A table of 8-hour ozone exceedance days for New England and each state from 1983 through 2008.
- Top four monitored 8-hour ozone concentrations during 1994-2008 for each New England monitor.
- 2005-2007 8-hour ozone design values by state and county. (PDF) (1 p., 109 KB, about PDF)
The number of exceedances in a given year is related to the number of days with elevated temperatures that year. View the graph of the total number of ozone exceedance days in New England versus high temperature days (i.e., those with maximum temperatures greater than 90°F) for the years 1983 to 2008.
In New England, the states operate a network of approximately 60 ozone monitoring stations during the ozone season (i.e., April 1 through September 30). View the locations of the ozone monitors.