Air quality is important to Southeast Michigan's quality of life. As the designated lead local air-quality planning agency under the federal Clean Air Act, SEMCOG is involved in a number of different activities to help attain and maintain national air quality standards in the region.

Ensuring that Transportation and Air Quality Plans Align

The Clean Air Act requires that SEMCOG’s long-range transportation plan and Transportation Improvement Program be consistent with the air quality goals established in the state air quality implementation plan (SIP). The process for demonstrating this consistency is called Air Quality Conformity. The purpose of Conformity is to ensure that projects in the plan will not cause new air quality violations, worsen any existing violations, or delay timely attainment of National Ambient Air Quality Standards (NAAQS). SEMCOG is responsible for ensuring this conformity is demonstrated. Download a copy of SEMCOG’s latest conformity analysis (pdf, 242KB).

Ozone Action – Promoting Public Involvement in Improving Air Quality

Through the Ozone Action Day program, SEMCOG helps everyone in the region understand that they have a role to play in keeping the air clean in Southeast Michigan. Ozone Action Days are called on hot, sunny days when heat and pollution emissions are expected to combine and create elevated concentrations of ground-level ozone, also called smog.

Quantifying Pollution from Cars and Trucks

In support of transportation and air quality planning activities, SEMCOG inventories emissions from on-road mobile sources (cars and trucks). Data from SEMCOG’s travel forecasting model, as well as the U.S. Environmental Protection Agency's (EPA) MOVES model, are used in this process.

Pinpointing Air Quality Problems and Identifying Cost-Effective Solutions

Under the federal Clean Air Act, each state must have a State Implementation Plan (SIP), which identifies how it will attain and/or maintain National Ambient Air Quality Standards (NAAQS). SEMCOG collaborates with the Michigan Department of Environmental Quality (MDEQ) and local stakeholders to prepare and update the SIP for Southeast Michigan. Examples of this work include evaluating the effectiveness of potential emission control measures, developing air quality attainment strategies, and coordinating Southeast Michigan’s air quality technical advisory group, which provides critical expertise on the science that drives our air quality.

Monitoring Compliance with National Air Quality Standards

SEMCOG regularly reviews air quality data from monitoring sites in southeast Michigan to track progress in attaining and maintaining the national standards.   The table below summarizes Southeast Michigan’s current air quality designations.

Current Air Quality Designations for Southeast Michigan 

Pollutant  Designation  Current Standard
(Year Established) 
Area  Transportation 
 Ozone Attainment  8-Hr: 75 ppb
2012  Entire region  No 
Attainment/Maintenance  35 ug/m3
2013 Entire region  Yes
Attainment 12 ug/m3
2015 Entire region Yes1
Attainment/Maintenance 1-Hr: 35 ppm
8-Hr:   9 ppm
1999 Portions of Wayne, Oakland
& Macomb counties 
 Sulfur Dioxide Nonattainment 1-Hr: 75 ppb
2013 Narrow strip of southeastern
Wayne County

1Until 1997 standard is officially revoked
2Until maintenance period ends in 2019
3Mobile sources are not a significant emissions contributor

Specific Air Quality Reports

A Conceptual Model for Ambient Fine Particulate Matter over Southeast Michigan: High Concentration Days (pdf, 3.2MB)

Passenger Vehicles and Air Pollution: A Profile of Southeast Michigan’s Fleet

Developing Regional Solutions
SEMCOG is a regional planning partnership of governmental units serving 4.7 million people in the seven-county region of Southeast Michigan striving to enhance the region's quality of life.