DefinitionDays (and person-days) in which the average concentration of ozone in outdoor air exceeds the regulatory standard at an ozone monitoring point
NumeratorNumber of days in a year in which the ozone concentration at a monitor exceeded the National Ambient Air Quality Standard (NAAQS), averaged over an 8-hour period; or exceeded the NAAQS of 0.12 ppm, averaged over a 1-hour period; or number of person-days, which is the product of the number of days with an ozone exceedance times the population of the geographic area (county) represented by a monitor.
Why Is This Important?Ozone is an odorless, colorless gas that forms both in the air at ground level and in the Earth's upper atmosphere (the stratosphere). Ground-level ozone forms when precursor pollutants that come from cars, power plants, and other sources react with each other in heat and sunlight.
While ozone in the stratosphere creates a layer that protects us from the sun's harmful ultraviolet (UV) rays, ozone at ground level may irritate and damage the lungs, and harm human health in other ways. The federal health-based standard for ozone in outdoor air was 0.075 parts per million (ppm) averaged over an 8-hour period until December 2015, at which time it was lowered to 0.070 ppm.
Other ObjectivesObjective 3A-2: Reduce the number of unhealthful days attributable to ozone to zero.
How Are We Doing?New Jersey has an extensive system of monitors to evaluate the quality of outdoor air. Twelve monitor sites operate year round, and 3 are operated only during the ozone season (April 1st through October 31st): Colliers Mills (Ocean County); Monmouth University (Monmouth County); and Ramapo (Bergen County).
Over the years, air quality in New Jersey has been improving. More stringent federal health-based standards for both ozone and particulates, were promulgated in 1997, and require states to do more to protect human health. New Jersey's air monitoring program evaluates hourly air quality readings using the national methodology called the Air Quality Index (AQI). The AQI uses five of the six pollutants for which there are national health-based standards (ground-level ozone, particulates, carbon monoxide, nitrogen dioxide and sulfur dioxide) and compares the composite pollutant levels to the federal standards in order to assign an air quality rating such as "good" or "unhealthy".
What Is Being Done?Under the federal Clean Air Act, the U.S. Environmental Protection Agency (USEPA) has set health-based standards for ozone in the air we breathe. The USEPA and state and local governments have instituted a variety of multi-faceted programs to meet these health-based standards.
The NJDEP has adopted rules to reduce emissions of VOCs from consumer products and establish requirements that apply to manufacturers, distributors, suppliers and retailers of VOCs. Beginning January 1, 2009, New Jersey implemented the California Low Emission Vehicle (CLEV) program. Non-regulatory programs also encourage communities to adopt practices such as carpooling to reduce harmful emissions. The NJDEP has also planted thousands of shade trees in urban areas to absorb and reduce ozone and NOx, lower temperatures, and reduce energy demand and emissions from energy generation.
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