Air Quality Monitoring

National Ambient Air Quality Standards (NAAQS)

The Clean Air Act (CAA) requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six criteria pollutants. Ozone and particulate matter are two of these pollutants.  EPA works with partners at state, local, and tribal air quality agencies to meet these standards.  In Michigan they primarily work through the Michigan Department of Environment, Great Lakes, and Energy (EGLE).

Under the CAA, as amended in 1990, each state must develop a plan describing how it will attain and maintain the NAAQS.  In other words, how it plans to clean up polluted areas and keep them clean.  This plan is called the State Implementation Plan (SIP) and is required under Section 110 of the CAA (40 CFR Part 51, Subparts F & G).  In general, the SIP is a collection of programs, including:

• a monitoring program, which is a collection of monitoring devices which provide actual measurements of the concentrations in the air, to identify whether an area is meeting the air quality standards

• air quality calculations and computer modeling, which are used to predict future trends and the effects of emission reduction strategies

• emissions inventories, which describe the sources and categories of emissions to the air for a given pollutant, and how much is emitted by each source or source category

Ozone Monitoring

A network of air quality monitoring stations located in Evans, Grand Rapids*, Holland, Jenison, and Muskegon, continually monitor ozone levels in West Michigan from April 1st through September 30th and post the data on the web. (*The Grand Rapids station monitors ozone year-round and posts the data on the web.) EGLE and the EPA average the data from these monitors over eight hours and compare it to the NAAQS. At each monitoring station, the fourth highest eight-hour value averaged over three years is not to exceed 70 parts per billion (ppb). If over three years, the average of the fourth highest ozone value is over 70 ppb, the NAAQS is violated.

For a map of these monitoring stations, click here.

Particulate Matter Monitoring

A network of air quality monitoring stations, located in Grand Rapids, Holland, and Jenison monitor West Michigan particulate matter levels year-round. EGLE and EPA use an annual standard and a daily standard to determine compliance with the particulate matter less than 2.5 um in diameter (PM2.5) NAAQS particulate matter violations. The EPA adopted a new annual standard of 9.0 micrograms per cubic meter (µg/m³) in Febuary, 2024. To attain this standard, the three-year average must not exceed 9.0 µg/m³. The previous standard of 12.0 µg/m³ is also still in effect. To attain the daily standard, the three-year average of the 98th percentile of 24-hour concentrations at each monitor must not exceed 35 µg/m³.

For a map of these monitoring stations, click here.

Monitoring and Clean Air Action Days

To help protect the health of the community, a Clean Air Action Day will be called on days when widespread ozone concentrations are forecast to exceed 70 ppb over an eight-hour period or particulate matter levels are forecast to exceed 35 µg/m³ over a 24-hour period throughout the area.

The Air Quality Index (AQI) is a tool used to communicate air quality to the public that is separate from the ozone and PM2.5 NAAQS. The AQI, normalized by pollutant concentration, ranges from good (green), moderate (yellow), unhealthy for sensitive groups (orange), to unhealthy (red).

For current air quality information, you can view ozone monitors or particulate matter monitors (MDEGLE web site) to see real time data from monitoring stations around the state. 

Clean Air Action Day Notifications in West Michigan

2024: May 18, June 17, June 19, July 14, August 27

2023: April 14, May 30, May 31, June 1, June 2, June 8*, June 21, June 22, June 24, June 27*, June 28*, June 29*, June 30**, July 1**, July 4, July 5, July 10, July 16*, July 17*, July 25*, July 27, July 28, August 23, August 24

2022: June 15, June 20, June 21, June 30, July 11, July 19

2021: May 21, June 5, June 6, August 28, August 29

2020: June 18, June 19, June 20, July 5, July 6, July 7, July 8th, July 9th, July 18th, August 26

2019: July 15, July 18, July 19, July 20

2018: May 25, May 27, May 28, June 16, June 17, June 29, June 30, July 1, July 9, July 13,
August 4, August 5

2017: June 10, June 11, June 12      

2016: May 23, June 10, June 11, June 19, June 25, July 21, July 23, August 4, August 10,
August 11

2015: July 18, August 16, August 17, September 6     

2014: July 20, July 21, July 22      

2013: August 20, August 21       

2012: May 24, May 27, June 9, June 10, June 15, June 16, June 19, June 20, June 28, June 29, July 2, July 3, July 4, July 5, July 6, July 7, July 13, July 15, July 16, July 17, August 4, August 24, August 25, August 30, August 31  

2011: June 7, June 8, July 2, July 17, July 20, July 21, September 1, September 2 

2010: July 4, August 13, August 29, August 30, August 31    

2009: June 24, August 15, August 16     

*Denotes an Action Day called for PM2.5. All other Action Days were called due to ground-level ozone (“smog”)
**Denotes an Action Day called for both Ozone and PM2.5.

Previous Ozone Action Day Notifications in West Michigan

2008: July 11, July 17, July 18, August 21, September 2

2007: June 16, June 18, August 1, August 2, August 28, September 5  

2006: June 17, July 16, July 17, July 31, August 1, August 2

2005: June 8, June 9, June 10, June 24, June 27, July 11, July 12, August 2, August 3, August 8, August 9

2004: June 8

2003: June 22, June 23, June 24, June 25, July 3, August 15, August 20, August 21

2002: June 9, June 10, June 20, June 23, June 24, June 25, June 30, July 1, July 15, July 16, July 17, July 31, August 1, September 8, September 9

2001: June 13, June 14, June 26, June 27, June 28, June 29, June 30, July 31, August 1, August 7, August 8, August 9

2000: June 9, June 10, Aug. 31, September 1

1999: May 29, June 6, June 7, June 8, June 9, June 10, June 22, June 25, June 26, June 27, July 3, July 4, July 5, July 15, July 16, July 23, July 30, September 3, September 4, September 5

1998: May 28, June 20, June 25, June 26, June 27, July 13, July 14, July 15, July 20, July 21, September 5

1997: June 24, June 27, June 28, June 29, June 30, July 1, July 12, July 13, July 14, July 17, July 26

1996: June 28, June 29, August 5, August 6, August 7, September 6

1995: June 6, June 7, June 15, June 16, June 17, June 18, June 19, June 20, June 21, July 12, July 13, July 14, July 15, July 30, July 31, August 12