Ground Level Ozone 

Oregon DEQ responds to new ozone standard

Ozone is a colorless, odorless gas that can be harmful to human health and plant life. In March 2008, the Environmental Protection Agency (EPA) determined that the 1997 primary ground level ozone standard, (a peak 1-hour average value of 0.08 ppm), was not protective enough of public health. The standard was revised to an 8-hour average value of 0.075 ppm. 

To address the new 8-hour ozone standard, DEQ drafted an update to the existing Portland-Vancouver Ozone Maintenance Plan, and developed a similar plan for the Salem-Keizer area. These plans, along with supporting rule revisions, ensure that ozone levels in the Portland and Salem areas will remain in compliance with federal health standards.

More About Ozone

Ozone is a colorless, odorless gas. In the Earth’s stratosphere (10 to 30 miles above the Earth’s surface), ozone helps to protect all life from the harmful rays of sunlight. However, ozone found at ground level is harmful to breathe.

Ground level ozone forms when nitrogen oxides and volatile organic compounds from motor vehicles, power plants and other sources react with sunlight to produce what is known as "smog". Ground level ozone is predominantly a summer time pollutant because sunlight and warm weather speed up the reaction. Ground level ozone occurs in urban and rural areas alike, due to the transport of ozone or the precursory pollutants that form it.

     Effects of ground level ozone:

• Public Health: Ground level ozone can reach levels high enough to produce respiratory health effects in people, and disproportionately affects children, older adults, and people with lung disease. Prolonged or repeated exposure has been shown to result in permanent lung damage, and can continue to occur even after symptoms subside.
  
• Vegetation: At ground level, ozone reduces the ability of plants to photosynthesize. Plants exposed to ground level ozone are more susceptible to damage by disease, pests, colder temperatures, and drought.
  
• Find more information on EPA’s Web site for Ground-level Ozone and the Oregon Environmental Public Health Tracking Web site.

Federal and State Ozone Standards

Under the federal Clean Air Act, EPA establishes primary and secondary National Ambient Air Quality Standards (NAAQS) for ground level ozone and five other pollutants, and works with state, local and tribal governments to meet these standards.

• Primary standards are set at levels intended to protect public health, particularly for "sensitive" populations (asthmatics, children, and the elderly).
  
• Secondary standards are intended to protect public welfare, for example, to reduce damage to agricultural crops; natural ecosystems; animals and man made structures; and visibility impairment.

Oregon currently defaults to the federal standard for acceptable ozone levels at the Earth’s surface. The EQC has directed DEQ to review the federal ozone standard and determine if it is sufficient to protect public health. If Oregon were to adopt EPA’s current standard, areas that have had problems in the past (Salem, Eugene, Medford and Portland) could violate the standards during severe inversion events.

Under the Clean Air Act, each state is required to submit to the EPA a State Implementation Plan (SIP) that identifies strategies to implement, maintain and enforce a new standard within three years after an area is designated as being in attainment (meeting the standard) or nonattainment (exceeding the standard). Under the old, 1-hour standard, Portland and Salem were nonattainment areas (meaning ground level ozone exceeded the standard). Both areas are designated as being in attainment under the new, 8-hour standard.

How ground-level ozone in Oregon compares to the new standard

The ozone standard was revised in 2008 from the three year average of the fourth highest eight hour average of 0.085 to 0.075 ppm. These graphs show how Oregon cities compare to both the old and new ozone standard. Figure 1 and 2 are the ozone trends for Oregon cities using the three year average of the fourth highest eight hour average. Figure 3 is the 2005-2007 ozone three year average of the fourth highest average ozone levels.

Figure 1. Ozone trends for Eugene, Medford, Portland and Salem using the three year average of the fourth highest eight hour average. The standard was revised in 2008 from 0.085 to 0.075ppm.

Figure 2. Detail of Figure 1 showing the years 2000 to 2007 only.

Figure 3. The 2005-2007 ozone three year average of the fourth highest average ozone levels for Eugene, Medford, Portland and Salem. The standard was revised in 2008 from 0.085 to 0.075ppm.

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