Ozone Information

Ground level ozone (O3) is regulated by the Environmental Protection Agency (EPA).  Under the EPA’s authority, the State of Colorado’s Air Quality Control Commission (AQCC) and the Air Pollution Control Division (APCD) are tasked with developing and enforcing regulations and implementing modeling and monitoring plans to reduce ozone concentrations and achieve the EPA’s designated National Ambient Air Quality Standards (NAAQS). Parts of Weld County are included in the EPA’s designated 8-hour ozone nonattainment area (NAA). 

Basic Ozone Information

Pollution + Heat and Sunlight = Ozone

The ozone molecule is composed of three oxygen atoms. It is formed by chemical reactions between natural and man-made ozone precursors, such as nitrogen oxides and volatile organic compounds, and the sun.  Whereas stratospheric ozone, or “good” ozone, found in the upper layers of earth’s atmosphere, protects us from solar radiation, tropospheric, also known as ground level or “bad” ozone, is a harmful air contaminant.  Inhalation of tropospheric ozone may cause detrimental short- and long-term health effects and elevated exposures can affect sensitive vegetation and ecosystems, including forests, parks, wildlife refuges, and wilderness areas. 

(Graphic Source:  climatecentral.org)  


For more information, visit:

EPA Ground-level Ozone Basics

CDPHE Ozone Pollution and Your Health.

Ozone Monitoring

Weld County Air Monitoring

Colorado Air Quality

National:

U.S. Air Quality Index
EPA Air Quality Monitors

Nonattainment Area Information

"" The EPA develops National Ambient Air Quality Standards (NAAQs) for criteria pollutants, such as ozone. Nonattainment Areas (NAA) are areas that have been designated as not meeting/attaining the ozone standard, or contributing to areas not meeting the ozone standard. Colorado's current NAA includes the lower three quarters of Weld County.

Areas designated as nonattainment areas undergo stricter air quality regulations to achieve attainment under the NAAQS, and States with nonattainment areas are tasked with developing implementation plans for meeting these federal standards within specific timeframes. The Colorado Department of Public Health and Environment maintains the State Implementation Plans (SIPs). 

In 2018, the Denver Metro/Northern Front Range (DM/NFR) was classified as marginal, under the 2015 8-hour ozone standard.  In 2020, the DM/NFR was re-classified from “marginal” to “serious" (nonattainment), under the 2008 8-hour ozone standard.

Based on the 2015 and 2008 8-hour ozone standard, the DM/NFR was, again, re-classified to “marginal” and  “serious” nonattainment, respectively, as of March 2022. The nonattainment boundary has since been reassessed, and the EPA determined that all of Weld County should be included in the nonattainment area for DM/NFR, effective December 30, 2021.

Weld County has submitted a letter commenting on the re-designation of northern Weld County(PDF, 3MB), and is currently waiting on a determination. 

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