What is Ozone?

Ozone (O₃) is commonly referred to as smog or haze and is associated with poor visibility in the summertime. Ground-level ozone differs from stratospheric ozone, the atmospheric layer that protects us from the sun's ultraviolet rays, and can be harmful to human health in high concentrations. Exposure to high levels of ozone can impair the function of lungs and may induce respiratory symptoms in individuals with asthma or emphysema. Ozone is a colorless, pungent gas that can reduce immune system capacity and irritate the eyes and throat.

Why is it Important?

Ozone is one of the six so-called "criteria" pollutants for which there is a National Ambient Air Quality Standard (NAAQS) as set in the federal Clean Air Act. The five other pollutants that fall under the NAAQS are: particulate matter (PM₁₀, or commonly referred to as soot), carbon monoxide (CO), sulfur dioxide (SO₂), Lead (Pb), and nitrogen dioxide (NO₂).

If a metropolitan area is in violation of the NAAQS, they must submit a plan (known as a State Implementation Plan) that describes how the region intends to comply with the standard in the near future. Those regions in violation of the standard, considered "nonattainment areas," are subject to withholding of federal transportation funds. As of June of 1997, there are 62 nonattainment areas for PM₁₀ nationwide and over 104 million people exposed to unhealthy levels of ozone. The last violation of the ozone standard in the Denver Region was in 1995.