Marquette, Mich.– The Michigan Department of Environmental Quality (MDEQ) Air Quality Division (AQD) develops air toxics screening levels which are health-based ambient air concentrations that provide public health protection. These screening levels are developed according to Part 55, Air Pollution Control, of the Natural Resources and Environmental Protection Act, 1994 PA 451, as amended. These screening levels are used in the implementation of Michigan’s air permitting rules that apply to new or modified sources that emit a toxic air contaminant and are required to obtain a Permit to Install. Under these rules, the emission of a toxic air contaminant cannot result in a maximum ambient air concentration that exceeds an applicable health-based screening level.

Historically, AQD toxicologists developed screening levels and posted them on the AQD web page, whereas the “justification” memos describing the bases for the screening levels were only available upon request. The public has always had the ability to comment to the AQD informally about the screening levels and how they were derived. Under rule revisions that went into effect on December 20, 2016, the AQD has formalized the comment process. The AQD will provide a 30-day formal public comment period on all health-based screening levels and their justifications.

A comment period is open and the Department of Environmental Quality is receiving comments on the following chemicals:

The comment period for the following listed chemicals starts March 15, 2018 and ends April 16, 2018. The list of screening levels and justification documents undergoing comment is given below.


CAS No.      Chemical Name        Screening Level*   Averaging Time   Public Comment: E-Mail AQD


145-73-3       Endothall                   Rescinded                       —                      Send Comment

335-67-1    Perfluorooctanoic Acid       0.07                     24-hour                Send Comment

1314-13-2     Zinc Oxide                          20                        8-hour                   Send Comment

1763-23-1   Perfluorooctanoic               0.07                     24-hour                Send Comment
Sulfonic Acid

7783-06-4    Hydrogen Sulfide             10                          Annual                  Send Comment

*micrograms per cubic meter (µg/m3)

Within 60 days of the close of the public comment period, the AQD will respond to all substantive comments received. The AQD will also post on this website the paraphrased comments for each toxic air contaminant and the AQD responses, including any changes to the screening levels resulting from addressing comments.

As directed by the rules, all screening levels are in effect immediately once established by the AQD, notwithstanding the formal public comment process. This is to provide clarity to permit applicants and ensure that permitting will be timely.

A comment may also be submitted by:

  • Going to the Air Toxics Screening Level Justification web page, then looking under the “Full List of Screening Levels & Justifications.”
  • Click on the link for chemicals arranged by Chemical Abstract Service (CAS) number or by chemical name. These lists provide the full list of over 1200 screening levels and show the chemicals available for formal public comment.
  • For chemicals open for formal comment, click on the link under “Is Public Comment Now Open?” Click on “E-Mail AQD” then select the link for the chemical you wish to comment on and then type your comments.
  • Please make sure to include your contact information at the end of your comment so staff may reach you if any clarification is needed.
  • If attaching files, please remember there is a 10 MB maximum.
  • The following file types are not allowed as attachments: EXE and MS Access databases.

Submit Press Releases, News, Calendar Items, and Community Events to Great Lakes Radio Stations WFXD, WKQS, WRUP, WQXO, and WPIQ
Click To Submit Press Releases, News, Calendar Items, and Community Events to Great Lakes Radio Stations WFXD, WKQS, WRUP, WQXO, and WPIQ