Draft Air Toxics Regulation Rulemaking
The MPCA published the draft Air Toxics Regulation Rulemaking on May 18, 2026. The draft Air Toxics Regulations will apply to facilities located within the seven-county metro area. Facilities with Registration Option A, Registration Option B, or Nonmetallic Mineral Processing General Permits are exempt from these requirements. Registration Option C Permit holders may be exempt, depending on the type of equipment at the facility.
The draft rule requires completion of the Screening Threshold for Regulated Air Toxics Analysis (STRATA) to determine if the facility emits air toxics above relevant screening thresholds. If a facility exceeds screening thresholds, they must either develop a Compliance Determination Protocol (CDP) or complete an Air Emissions Risk Analysis (AERA). If the AERA yields results above acceptable risk levels, the facility can either develop a CDP or complete an Air Toxics Reduction Plan (ATRP).
STRATA
The first step in compliance with the draft Air Toxics Regulations is to complete a STRATA. Deadlines for the completion of the STRATA are as follows:
- Individual Permit – Within 1 Year of Final Rule
- Capped Permit and General Permit – Within 2 Years of Final Rule
- Registration Option C and D Permit – Within 3 Years of Final Rule
The STRATA tool is an Excel-based spreadsheet that is populated with facility stack parameters (such as stack height and distance to property line) and actual emissions as reported in the most recent air emission inventory. Certain emission units are exempt from being included in the STRATA tool, such as emergency generators, insignificant activities, and comfort heating units combusting natural gas. Similarly, HAP emissions regulated under a federal standard are exempt from being included in the STRATA tool.
Once completed, the STRATA tool must be recertified every 5 years. If the STRATA tool indicates the facility has air toxics emissions above screening threshold values (STVs), the facility must choose to develop a CDP or complete an AERA.
CDP
If a facility has air toxics emissions above screening levels, the facility must either develop a CDP to lower air toxics emissions or complete an AERA. A CDP must contain the following elements:
- List the name and CAS number for each air toxics above STVs,
- Description of each process (i.e. EQUI ID) which emits the air toxic(s) above STVs,
- Description of voluntary limits or practices the facility will implement to lower relevant air toxics emissions,
- An example of this could be limiting the operating hours of affected equipment.
- Note, CDPs are considered federally enforceable.
- Description of emissions rate measurement method, and
- Description of records used to verify compliance.
The facility’s CDP is due 1 year after the facility’s STRATA deadline. Any deviations from the CDP must be reported in the facility’s semiannual deviation report. When a CDP is in place, a facility only needs to recertify the STRATA every 10 years.
AERA
If a facility is above STVs, the facility can choose either to develop a CDP to lower air toxics emissions to stay below the STVs or complete an AERA. The MPCA’s AERA procedure is already utilized for other permitting procedures, such as Environmental Review. A key difference between completing an AERA and a STRATA is that potential to emit (PTE) values are utilized in an AERA, rather than actual emissions, as with the STRATA. Similarly, the AERA considers the cumulative impacts of a facility, rather than a pollutant-by-pollutant basis, as with the STRATA.
The AERA requires completion of an AERA protocol, as detailed in the AERA Checklist. The protocol must be submitted to the agency and approved prior to completing the AERA report. An AERA may require air dispersion modeling as well as completion of the Risk Assessment Screening Spreadsheet (RASS).
If the AERA shows the facility exceeds acceptable risk levels, the facility can choose to either refine the AERA, develop a CDP to lower air toxics emissions to stay below the STVs, or complete an ATRP. The facility’s compliant AERA is due 1 year after the relevant STRATA deadline. STRATA recertification is not required if a compliant AERA is completed.
ATRP
An ATRP is required if the facility has completed a AERA exceeding acceptable risks and does not want to develop a CDP. An ATRP must be developed within 1 year of the completion of the non-passing AERA, and must include the following items:
- Description of targeted air toxics being reduced,
- Description of each process which emits air toxics above STVs,
- Air toxics reduction actions and related timelines,
- May involve installing control equipment.
- Description of measurement method, and
- Description of records used to verify compliance.
The ATRP path requires notification to the public when the draft ATRP is ready, when the ATRP has been approved by the MPCA, and when reduction actions have been completed.
Once developed, the draft ATRP is reviewed by the MPCA. If approved, the ATRP must be implemented within 2-3 years (depending on whether add-on controls are required) and resident notifications must be sent. Semiannual progress reports must be submitted, and a major amendment must be submitted to incorporate the ATRP into the facility’s permit.
Air Toxics Reporting
Separate from the draft Air Toxics Regulations, on October 6, 2025, the Minnesota Pollution Control Agency (MPCA) adopted new rules regarding annual air toxics emissions reporting for air permitted facilities within the seven-county metro area. All air permitted facilities, with the exception of those under an Option B registration permit, in the seven-country metro will be required to report air toxics emissions annually, starting in the reporting year (RY) 2026 Air Emissions Inventory, due April 1, 2027.
For the majority of facilities, reporting air toxics will involve the same process as reporting criteria pollutants. A facility can either use continuous emission monitor data, performance test data, material balance, emission factors, or enforceable limitations to calculate reported emissions. For air permittees with an Option C Registration permit, air permittees must also now report the weight factor of air toxics in the VOC-containing materials and the density of the material.
In an email sent out to permit holders on December 16, 2025, the MPCA explained that for air permittees with a Registration Permit Option D, Option D Hot Mix, or Nonmetallic General Permit, the MPCA will directly calculate air toxics for fuel-burning activities based on reported fuel use. If a facility with a Registration Permit Option D chooses to determine air toxics emissions separately, the facility must keep records of emissions and calculations. Similar to Option C permit holders, any calculations relying on material balance will require a review of composition data for any materials.
RY2026 Annual Emission Inventory Considerations
The RY2026 Annual Emission Inventory should undergo extra scrutiny for facilities subject to the draft Air Toxics Regulations, as RY2026 reported air toxics emissions will be utilized to populate the STRATA tool. It is important to verify that references and methodologies used for determining air toxics emissions are representative rather than overly conservative.
Verifying air toxics emissions may include obtaining up-to-date safety data sheets (SDS) to have an accurate understanding of the chemical components that may need to be reported and tracking throughputs of all materials at the facility. De minimis standards provided in Minn. R. 7019.3110 Subp. 3 should be reviewed prior to reporting an air toxic. Certain air toxics must be reported, regardless of whether they are below the de minimis standard; these mandatory chemicals are listed under Minn. R. 7019.3110 Subp. 3.B.
A facility may want to update its emission tracking spreadsheet with template calculations provided by the MPCA. Using the same calculation methodologies as the agency will ensure a smoother process of validating an emission inventory. This can be especially helpful for facilities with Option C or D Registration Permits, as the MPCA plans to automatically calculate emissions using fuel usage data. Facilities can ensure that the calculations calculated with the MPCA’s reporting portal are correct by comparing the values in the emission inventory with the values using the template calculations.
The parameters a facility is already tracking to calculate criteria pollutants emissions are likely the same parameters that will be used to calculate air toxics emissions. However, beyond operating parameters, facilities will need to determine appropriate air toxics emission factors, which could come from performance testing, manufacturer data, or other acceptable references.
The new rule also allows for a reduction in air toxics emissions due to recycling or disposing of material off-site. In this situation, facilities must keep records of the amount of disposed material, the amount of material shipped off-site for recycling, and calculations to determine how much of a reduction can be taken. These records can include SDS, invoices, shipping papers, and hazardous waste manifests.
Trinity is Here to Assist
Trinity has been following the Air Toxics Reporting and Draft Air Toxics rulemakings closely. For more relevant information, see the article and webinar below:
If you have questions about the Air Toxics Reporting and Draft Air Toxics Rule, Trinity is available to support. For more information on this topic, please contact Jena DeRung via email or Trinity’s Minneapolis Office at 651.275.9900.
