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Updates to air toxics reporting

In October 2025, the MPCA adopted new rules for air toxics emissions reporting, as directed by the 2023 Legislature. 

Previously, facilities with air permits voluntarily reported air toxics emissions every three years. The new rule will require air permitted facilities (except registration option B permits) operating in the seven metropolitan counties (Anoka, Carver, Dakota, Hennepin, Ramsey, Scott, and Washington) to report air toxics emissions each year starting with the 2026 Emissions Inventory, due April 1, 2027. 

MPCA will continue to strongly encourage facilities operating outside the seven metropolitan counties to continue to voluntarily report air toxics emissions.

Air toxics reporting list

Air toxics are pollutants that are known or suspected to cause cancer or other serious health effects or adverse environmental or ecological effects. Air toxics in the new air toxics reporting rule (Minn. R. 7019.3110) include:

The MPCA will maintain a comprehensive air toxics reporting list (AT List) that facilities in the seven metropolitan counties are required to report. The AT List will be reviewed and potentially updated again prior to the start of the 2026 emissions inventory reporting period.

The AT List:

  • includes an ‘About’ tab with additional information and guidance
  • includes all air toxics to be reported and associated CAS numbers (if available) in columns: ‘Pollutant Code’, ‘Short Description’, ‘Cas No. with (-)’, and ‘Cas No. without (-)’
  • indicates the pollutant group (column: ‘Pollutant Group’) that individual pollutants belong to (e.g., Cobalt Compounds) for which there is group-based reporting guidance outlined below. 
    Note: the individual pollutants listed under the metals, cyanide, and particulate organic matter (POM) groups are not exhaustive. Refer to specific group guidance below for more information.
  • indicates if the air toxic is a HAP or not a HAP (column: ‘HAP or Other Air Toxic’)
  • specifies the de minimis threshold for each pollutant (column: ‘De Minimis’), indicating the concentration of a chemical in a mixture at which the chemical must be reported. For facilities using the material balance approach to estimate emissions, applicable thresholds include no (no de minimis), 0.1%, and 1.0%.

Guidance for reporting pollutants that are part of groups

Generally, this guidance is intended for facilities using the material balance approach to estimate air toxics emissions.

Pollutant groups include metals and metal compounds, cyanide and cyanide compounds, glycol ethers, polycyclic organic matter (POM), cresols, lindanes, xylenes, dioxins/furans, PFAS, 2,4-D salts and esters, and polychlorinated biphenyls (PCBs). See below for specific guidance for each group. For metals and cyanide groups, facilities are required to report any chemical substance that contains the named chemical as part of the chemical’s infrastructure. For example, cobalt carbonate must be reported because it contains ‘cobalt,’ even if it’s not individually listed on the AT List (see guidance below). 

Previous reporting strategy for groups. Previously, facilities had two options for voluntary reporting of air toxics that were part of groups: they could either report each individual pollutant within a group, or in cases where individual compounds could not be reported, report total emissions under the group. Only one reporting strategy per group per process could be used. 

New reporting strategy for groups – Change from previous guidance. The new Air Toxics Emissions Reporting Rule requires facilities operating in the seven metropolitan counties to report individual pollutants for pollutants within a group to the maximum extent feasible. In most cases, facilities must report all individual pollutants known and report any remaining emissions under the ‘UNSPECIFIED’ or ‘OTHER’ groups as described under each section below. The MPCA will be updating e-Services to allow for this new reporting strategy and develop additional guidance prior to the start of 2026 reporting. 

In the new reporting strategy, there are a few ways for reporting pollutants that are part of groups. The strategies differ depending on the group type and on the information know and provided on the safety data sheet (SDS). See each pollutant group below for specific information.

Metal and cyanide groups

The guidance should be used for facilities reporting emissions of metals and metal compounds and cyanide and cyanide compounds. This guidance applies to the following air toxics and the associated compounds: aluminum, antimony, arsenic, beryllium, cadmium, chromium, cobalt, copper, cyanide, lead, manganese, mercury, nickel, selenium, vanadium, and zinc.

Any compound that contains the metal or cyanide must be reported. For example, if a SDS identifies cobalt carbonate, the facility must report emissions from the compound because it contains ‘cobalt,’ even if the specific pollutant is not individually included on the AT List. The AT List is not an exhaustive list of all individual metals and cyanides included in the pollutant group.

In the new reporting strategy, there are three reporting strategies for reporting pollutants that are part of metal and cyanide groups, depending on the information known and provided on the safety data sheet (SDS). See below for guidance.

Each individual pollutant within the group can be reported individually for a given unit/process:

  • separately report emissions of each individual metal or cyanide compound known (listed with a CAS number on the SDS) and that are included on the AT List; do not aggregate emissions and report under the group
  • each individual compound must be reported as the mass of the total compound, not just the metal within the compound
    • note: if the SDS lists the group name and associated CAS number (e.g., arsenic, CAS: 7440-38-2), report emissions under pollutant code: ARSENIC

Some individual pollutants within the group can be reported individually for a given unit/process:

  • Separately report emissions of each individual metal or cyanide compound known and that are included on the AT List. Each individual compound must be reported as the mass of the total compound, not just the metal within the compound. Do not aggregate emissions and report under the group pollutant code (e.g., ARSENIC,OTH)
    • note: if the SDS lists the group name and associated CAS number (e.g., arsenic, CAS: 7440-38-2), report emissions under pollutant code: ARSENIC.  
  • Aggregate and report all remaining emissions of all individual pollutants known (listed on the SDS with a CAS number) but are not included on the AT List as the metal or cyanide within the compound under the ‘OTHER’ metal or cyanide pollutant code (e.g., ARSENIC,OTH). 

How to report emissions as the metal or cyanide:

  • estimate the amount of metal or cyanide emitted by dividing the molar mass of the metal or cyanide (mass of 1 mole of the metal) by the molar mass of the compound and multiplying the result by the amount of the compound
  • example: A facility emits 1 ton of calcium arsenate (CAS No. 7778-44-1). This specific arsenic compound is included on the SDS but is not included on the AT List and cannot be reported separately in e-Services. Therefore, the facility should report emissions under ARSENIC, OTHER.
  • Step 1: determine the molar mass of arsenic and calcium arsenate (Ca3(AsO4)2):
    • Arsenic molar mass: 149.84 g arsenic/mol calcium arsenate
    • Calcium arsenate molar mass: 398.07 g calcium arsenate/mol calcium arsenate
    • MPCA recommends using PubChem (nih.gov) to determine the molar mass of a compound.
  • Step 2: calculate the fraction of arsenic in the compound by dividing the arsenic molar mass by the calcium arsenate molar mass:
    • 149.84 / 398.07 = 0.38, 38% of the compound’s mass is the metal portion (arsenic)
  • Step 3: calculate the metal portion of the emissions to be reported:
    • 1 ton calcium arsenate x 0.38 = 0.38 tons arsenic
  • The facility would report 0.38 tons emissions under pollutant code: ARSENIC,OTH, short description: ARSENIC, OTHER (AS ARSENIC)

No individual pollutants within the group can be reported individually for a given unit/process:

  • aggregate and report all emissions of individual pollutants that are not included on the AT List as the metal or cyanide within the compound under the ‘OTHER’ metal or cyanide pollutant code (e.g., ARSENIC,OTH, short description: ARESENIC, OTHER (AS ARSENIC)
    • see instructions above (How to report emissions as the metal or cyanide)

Chromium

  • since there is widely varying toxicity, facilities need to separate chromium compounds into chromium III and chromium VI, if possible
  • separately report each individual chromium compound known that is included on the AT List as the mass of the individual compound
  • aggregate and report any remaining emissions of individual chromium pollutants known that are not included on the AT List as chromium III and/or chromium VI under pollutant code: CHROMIUMIII,OTH and/or CHROMIUMVI,OTH, short description: CHROMIUM (III), OTHER and/or CHROMIUM (VI), OTHER, respectively
    • note: if the SDS lists the group name and associated CAS number (e.g. chromium, CAS: 7440-47-3), report emissions under pollutant code: CHROMIUM
    • report these emissions the same as the other metals and cyanides. see instructions above (How to report emissions as the metal or cyanide)
  • if no individual compounds can be reported, aggregate and report all emissions of chromium known that are not included on the AT List as chromium III and/or chromium VI under pollutant code: CHROMIUMIII,OTH and/or CHROMIUMVI,OTH, short description: CHROMIUM (III), OTHER and/or CHROMIUM (VI), OTHER, respectively
    • report these emissions the same as the other metals and cyanides; see instructions above (How to report emissions as the metal or cyanide)
Glycol ethers

All individual glycol ethers are shown on the AT List. Filter column ‘Pollutant Group’ for ‘glycol ethers’ to see all glycol ethers included in the reporting rule.

EPA uses the Toxics Release Inventory (TRI) List of Toxic Chemicals within the Glycol Ethers Category to determine if a chemical falls into a glycol ether category. If the chemical is not listed in Table 1 of the above guidance, please use this structural definition provided by EPA to determine if the chemical is a glycol ether:

mono- and di-ethers of ethylene glycol, diethylene glycol, and triethylene glycol
R - (OCH2CH2)n - OR'  where
n = 1, 2 or 3
R = alkyl C7 or less; or R = phenyl or alkyl substituted phenyl
R' = H or alkyl C7 or less; or OR' consisting of carboxylic acid ester, sulfate, phosphate, nitrate, or sulfonate

In the new reporting strategy, there are three scenarios when reporting emissions for pollutants that are within the glycol ether pollutant group. See below for guidance for each scenario.

All individual glycol ethers can be reported individually for a given unit/process:

  • separately report emissions of each individual glycol ether known, included on the SDS, and on the AT List; do not aggregate emissions and report under the group pollutant code: GLYCOL ETHRS, short description: GLYCOL ETHERS - UNSPECIFIED

Some individual pollutants within the group can be reported individually for a given unit/process:

  • separately report emissions of each known individual glycol ether that are known and individually included on the AT List; do not aggregate these emissions and report under pollutant code: GLYCOL ETHRS, short description: GLYCOL ETHERS - UNSPECIFIED
  • separately report any remaining emissions under pollutant code: GLYCOL ETHRS, short description: GLYCOL ETHERS - UNSPECIFIED

No individual pollutants within the group can be reported individually for a given unit/process:

  • report all emissions under GLYCOL ETHRS, short description: GLYCOL ETHERS - UNSPECIFIED
Polycyclic organic matter (POM)

The POM group contains over 100 pollutants. Filter column: ‘Pollutant Groups’ for ‘POLYCYCLIC ORGANIC MATTER’ to see all individual POMs in the AT List. Note the POLYCYCLIC ORGANIC MATTER group includes Polycyclic Aromatic Hydrocarbons (PAHs).  

In the new reporting strategy, there are three scenarios when reporting emissions for pollutants that are within the POM group. See below for general guidance for each scenario:

All individual POMs can be reported individually for a given unit/process:

  • separately report emissions of each individual POM known and that is included as an individual pollutant on the AT List; do not aggregate emissions and report under the pollutant code: PAH/POM, short description: PAH/POM - UNSPECIFIED

Some individual POMs can be reported individually for a given unit/process:

  • separately report emissions of each known individual POM that is included on the AT List; do not aggregate these emissions and report under pollutant code: PAH/POM, short description: PAH/POM - UNSPECIFIED
  • separately report any remaining emissions under pollutant code: PAH/POM, short description: PAH/POM - UNSPECIFIED)

No individual POMs can be reported individually for a given unit/process:

  • aggregate and report all emissions under pollutant code: PAH/POM, short description: PAH/POM - UNSPECIFIED
Cresols, lindanes, xylenes

All individual isomers that are included in the cresols, lindanes, xylenes are shown on the AT List. There are two scenarios when reporting emissions for pollutants that are within these groups, depending on the information known and what is provided on the safety data sheet (SDS).

  • separately report emissions of each known individual isomer that is included on the AT List
  • separately report any remaining emissions under the group (e.g., pollutant code: CRESOL MX IS), short description: CRESOLS (MIXED ISOMERS)
Dioxins/furans

Report the mass of the 17 individual congeners of chlorinated dibenzodioxins (CDDs) and chlorinated dibenzofurans (CDFs) included on the AT List. Filter column ‘Pollutant Group’ for DIOXINS/FURANS.

Per- and polyfluoroalkyl substances (PFAS)

The reporting for PFAS has changed with the new Air Toxics Reporting Rule. For the 2026 emission inventory, all PFAS that are required to be reported are listed on the AT List. The PFAS group contains about 280 individual PFAS pollutants. Filter column ‘Pollutant Groups’ for ‘PFAS’ to see all PFAS pollutants that can be reported. 

There is no ‘PFAS’ pollutant group under which individual PFAS not included on the AT List can be reported. Therefore, any PFAS not included on the AT List do not need to be reported.

For assistance identifying PFAS compounds in the materials you use, refer to the fact sheets below.

For questions about PFAS reporting, contact Joe Miller.

2,4-D salts and esters and polychlorinated biphenyls (PCBs)

Separately report emissions of each known individual pollutant that is included on the AT List. Any individual pollutants in these two groups that are not included on the AT List do not need to be reported. There are no ‘2,4-D salts and esters’ or ‘polychlorinated biphenyls’ pollutant groups under which additional individual pollutants in these two groups can be reported.