MDEQ Air Toxics Screening Level Justifications

With the comment period wrapping-up on April 16, 2018, there are five chemicals to be aware of related to air emissions permitting in Michigan:

Endothall (CAS # 145-73-3), Screening Level Rescinded
Perfluorooctanoic Acid (PFOA) (#335-67-1), 0.07 ug/m3, 24-hour Avg/Time
Perfluorooctanoic Sulfonic Acid (PFOS) (#1763-23-1) 0.07 ug/m3, 24-hour Avg/Time
Zinc Oxide (#1314-13-2) 20 ug/m3, 8-hour Avg/Time
Hydrogen Sulfide (#7783-06-4) 10 ug/m3, Annual Avg/Time

PFOA and PFOS have become an emerging regulatory topic in Michigan based upon the presence of PFAS compounds identified at several high-profile sites throughout the state. The addition of PFOA and PFOS to air permitting guidelines will be the first of its kind in Michigan.

Michigan rules state that screening levels are effective immediately once established by the MDEQ Air Quality Division (AQD) notwithstanding the formal public comment process. The purpose of the immediately effective rule is to provide clarity to permit applicants and ensure that permitting will be timely.

According to the Air Toxics Screening Level Justifications published by the MDEQ, the AQD develops air toxics screening levels that are health-based ambient air concentrations to 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. The screening levels are used in the implementation of 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.