History of Air Quality in West Michigan

The United States Environmental Protection Agency (EPA) and the state of Michigan together share responsibility for implementing federal Clean Air Act requirements.  In this capacity, the Michigan Department of Environment, Great Lakes, & Energy (EGLE) monitors air pollution levels and works with local community government and planning agencies to develop attainment plans that bring areas in violation of air quality standards into compliance.

The West Michigan Clean Air Coalition, in cooperation with its members and partners as well as the EGLE, works to promote measures that improve air quality throughout the region. Below is a brief history of ozone and particulate matter air quality compliance in West Michigan and our historic progress improving air quality for this area.

Ozone Standards

The 1-Hour Standard

The old ozone standard was an exceedance-based calculation where a violation occurred if a monitor recorded more than three days where the 1-hour ozone values were greater than 124 parts per billion in a three-year period.  From 1978 through 1994, Kent, Ottawa, Muskegon, and Allegan Counties were designated as nonattainment areas because ozone levels exceeded the standard. 

Over 20 years of emission control efforts resulted in the West Michigan counties meeting the 1-hour ozone standard.  The improvement in air quality qualified these areas to be redesignated as “attainment areas.”  The Kent and Ottawa County area was redesignated as attainment in 1996.  Muskegon was redesignated as attainment in 2000, and Allegan County became in attainment in 2001.  As of June 15, 2005, all areas in Michigan are no longer subject to the 1-hour ozone standard.

The 8-Hour Standard

In 1997, the EPA adopted a more stringent 8-hour ozone standard.  This standard is based on concentration levels averaged over an 8-hour period instead of the number of exceedances.  The 8-hour standard was considered more protective of public health for population groups especially sensitive to air pollution--children who are active outdoors, adults engaged in moderate to strenuous outdoor activities, and individuals with respiratory disease, such as asthma. 

Designations for the 8-hour ozone standard were made by the EPA on June 15, 2004.  In West Michigan, Kent, Ottawa, Muskegon, and Allegan were all designated as nonattainment.  The Muskegon nonattainment area was also classified as marginal based on the severity of the ozone pollution measured there.  Overall air quality has since improved in West Michigan, and in response to requests by the Michigan Department of Environment, Great Lakes, & Energy (EGLE), EPA has redesignated Kent, Ottawa, Muskegon, and Allegan Counties as attainment for the 1997 8-hour ozone standard. 

The National Ambient Air Quality Standards for ozone were revised in March of 2008. The 2008 NAAQS standard for ground-level ozone was set at 0.075 ppm for an 8-hour period. The EPA also specified the level of the standard to the nearest thousandth of a ppm (aka the "third decimal place"), which eliminated the need for rounding under the new standard.  

Particulate Matter Standards

National Ambient Air Quality Standards (NAAQS) for particulate matter were first set in 1971. Total suspended particulate (TSP) was the first indicator used to represent suspended particles in the ambient air. There were secondary standards, which were welfare standards, and primary standards, which were public health standards. An area in Kent County was designated nonattainment of the secondary TSP standard in 1978. An area in Muskegon County was also designated as exceeding the secondary standard in 1978, with a correction in 1981. 

In 1987, the standard was changed to PM10, or particulate matter with an aerodynamic diameter less than 10 microns. There were no nonattainment areas in West Michigan for this standard.

In 1997, the EPA established an annual standard and a 24-hour standard for PM2.5, or particulate matter with an aerodynamic diameter less than 2.5 microns. The PM10 standard remained in place. The first nonattainment designations for the 1997 standard were made in 2005. No areas in West Michigan were in nonattainment.

In 2006, the EPA revised the 24-hour PM2.5 standard and retained the existing annual PM2.5 standard. The NAAQS 24-hour standard set in 2006 for fine particulate matter remains 35 µg/m³. The previous 24-hour standard of 65 µg/m³ was established in July of 1997 . The annual standard for particulate matter of 15 µg/m³ was established in 1997 and remains in effect today. Particulate matter levels in West Michigan were exceptionally high in 2005, and therefore, the design value for Kent County for 2004-2006 was 37 ug/m3 and for 2005-2007 was 36 ug/m3. The 24-hour NAAQS is set at 35 ug/m3.

The EPA sent Governor Granholm a letter dated August 18, 2008, indicating that Kent and Ottawa Counties should be designated as nonattainment for the 2006 24-hour PM2.5 standard based on monitored data from 2005-2007.

On December 22, 2008, EPA signed a final notice listing Kent and Ottawa Counties as nonattainment. This notice was never published in the Federal Register, and the designation did not become effective. Because air quality monitoring for 2008 was nearly complete, EPA agreed to evaluate the status of an area based on 24-hour PM2.5 air quality data from 2006-2008 if a state submitted complete, quality-assured, certified air quality data for 2008 before the designations became effective. 

On October 8, 2009, EPA published final designations for the 2006 24-hour PM2.5 standard using 2006-2008 data. Kent and Ottawa were designated as attainment. 

As of 2013, the only area in Michigan that has been designated as nonattainment for the annual and 24-hr PM2.5 standards is SE Michigan. All monitors in the state are meeting both the 24-hour and annual PM2.5 standards since 2009. Redesignation to attainment for SE Michigan was proposed by EPA on July 2, 2013. All monitors in the state are also meeting the new 2012 annual NAAQS of 12 ug/m3.

Recent Revisions of the National Ambient Air Quality Standards (NAAQS)

On October 1, 2015, EPA strengthened the National Ambient Air Quality Standards (NAAQS) for ground-level ozone to 70 parts per billion (ppb) based on extensive scientific evidence about ozone’s effects on public health and welfare. The updated standards will improve public health protection, particularly for at-risk groups including children, older adults, people of all ages who have lung diseases such as asthma, and people who are active outdoors, especially outdoor workers. They also will improve the health of trees, plants and ecosystems. 

The MDEQ operates a network of air quality monitors in several West Michigan counties.  Ozone monitors operate continuously from March 1st through October 31st. This data is posted in near real-time to www.deqmiair.org .  The Michigan Department of Environment, Great Lakes, & Energy (EGLE) also operates monitors to measure fine particulate matter and other pollutants year-round at many West Michigan sites. Annual air quality reports, which contain all of the statewide air monitoring data, are available online.

The Air Quality Index (AQI) and Clean Air Action

The AQI is a color-coded daily air health indicator that provides a snapshot of current air quality to the public.  Both fine particulate matter and ground-level ozone levels are reported through the AQI.  The AQI ozone breakpoint of 70 parts per billion (or 0.070 parts per million) and the AQI particulate matter breakpoint of 35.5 µg/m³ are the “unhealthy for sensitive groups” (orange) category which represents the population at greatest risk.  When ozone or particulate matter levels are expected to approach or exceed that level, Clean Air Action Days are declared and individuals and businesses are asked to take part in voluntary emission reduction activities to reduce pollution.  The number of high pollution days fluctuates each year according to the weather conditions.

Daily AQI values should not be confused with the 8-hour ozone standard or the fine particulate matter average-based standards.  The AQI and the air quality standards are not interchangeable.