The Missouri Department of Natural Resources monitors ozone across the state during the ozone season, which begins March 1 and ends October 31. Naturally occurring ozone in the upper atmosphere protects the earth from the sun's harmful rays. Ground-level ozone, commonly known as smog, is a gas that is created when pollution from vehicles, businesses and power plants combine in the presence of sunlight. The pollutant is formed when heat and sunlight mix with volatile organic compounds, or VOCs, and nitrogen oxides, or NOx, in the lower atmosphere. Typically, ozone pollution is more of a problem in the hot summer months because sunlight and warm temperatures speed up the formation of ground-level ozone.

Health Effects

Exposure to ground-level ozone can contribute to health and environmental problems. Ground-level ozone is an irritant that damages lung tissue and aggravates respiratory disease. Ozone can trigger a variety of health problems. Those most susceptible to ozone include children, the elderly and individuals with pre-existing respiratory problems. Children are at increased risk from exposure to ground-level ozone because their lungs are still developing. Healthy adults can experience problems breathing, especially those who exercise or work outdoors.

Reducing Ozone

Simple everyday steps can help reduce the emission of harmful pollutants that are derived from vehicles and coal-fired power plants that produce our energy. These emissions contribute to the formation of ground-level ozone.

Ozone-reducing activities include:

  • Use mass transit, carpool, bike or walk.
  • Do not top off gas tanks. Stop at the first click.
  • Do not use gas-powered lawn equipment on hot, sunny days with little or no wind. Consider waiting until early evening to mow your lawn.
  • Conserve energy by turning off lights and appliances when leaving a room to reduce emissions from power plants. Purchase Energy Star® appliances.
  • Set goals to reduce utility bills by two percent. This can save money and protect air quality.
  • Keep tires properly inflated.

For even more tips, visit cleanair-stlouis.com.

Ozone Standards

The first ozone NAAQS was published in 1979. The standard was based on one-hour average concentrations. In 1997, EPA revised the ozone NAAQS and the new standard was based on a design value stemming from 8-hour average concentrations. In 2008, and again in 2015, EPA revised the ozone standard. The 2008 standard and subsequently the 2015 standard were lowered, but they were still based on a design value stemming from 8-hour average concentrations.

8-hr Ozone Standard: 70 parts per billion, or ppb

Date EPA Approval Document
Submitted: September 22, 2017   Letter to EPA on 2015 Ozone Recommendation

Submitted: September 2016

2015 Ozone Standard Area Boundary Designation Recommendation

Appendix A - HYSPLIT Back Trajectories

Eight-hour Ozone Standard: 75 parts per billion, or ppb

On Sept. 22, 2011, the U.S. Environmental Protection Agency released a memorandum to clarify for states the status of the 2008 Ozone National Ambient Air Quality Standard. In this document, EPA explicitly stated that the current standard is 0.075 parts per million, or 75 parts per billion. This standard is based on a three year design value, which is calculated by taking the fourth highest daily high 8-hour average concentration recorded each year, for three years and averaging the three years together.

Boundary Recommendations

Date Document

Submitted:
December 2011

Revised 2008 8-Hour Ozone Boundary Recommendation

Received:
December 2011

EPA 120-day Letter for the 2008 8-hour Ozone Boundary Designations
Attachment to EPA 120-day Letter

Submitted:
March 2009

Original 2008 8-Hour Ozone Boundary Recommendation
Ozone Boundary Recommendation Letter to the U.S. Environmental Protection Agency

Technical Support Documents and Other Attachments for the Original 2008 8-Hour Ozone Boundary Recommendation.

Missouri Summary of Area Ozone Recommendations

St. Louis Area and Southeast Missouri Area Recommendations

Kansas City Ozone Recommendation

Springfield and Southwest Missouri Ozone Recommendation

Appendix A - Meteorological Analysis

Appendix B - Responses to Comments on the Ozone Boundary Recommendation

Appendix C - Written Comments Received on the Proposed Ozone Boundary Recommendation

Infrastructure SIP

Date EPA Approval Document

MACC Adoption: June 2013

Pending

Missouri State Implementation Plan Revision –  Section 110 Infrastructure SIP for the 2008 Ozone NAAQS

St. Louis Area

Date EPA Approval Document
Submitted:
July 27, 2017
 

Redesignation Request and Maintenance Plan-Discussion of Emissions

Submitted: November 2016

Clarification Letter on Redesignation and Maintenance Plan

Submitted: September 2016

Redesignation Request and Maintenance Plan for the St. Louis (Missouri) 2008 Ozone Standard Nonattainment Area

Submitted: September 2014

Marginal Area Plan for the Missouri Portion of the St. Louis Nonattainment Area for the 2008 8-Hour Ground Level Ozone National Ambient Air Quality Standard

MACC Adoption: March 2013

Pending

Early Progress Plan for the Missouri Portion of the St. Louis Nonattainment Area for the 2008 Ground-Level Ozone National Ambient Air Quality Standard

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