Pollutant categories for air toxics

There are 204 individual air toxic (AT) chemicals and 830 chemicals within 29 groups included in the air toxics emission inventory. This list includes the 188 hazardous air pollutants (HAPs) identified by the Environmental Protection Agency (EPA) and other individual pollutants that are part of HAP groups, pollutants in the Great Lakes regional air toxics emission inventory project, and pollutants of concern in Minnesota’s outdoor air. The list also includes 428 new per- and polyfluoroalkyl substances (PFAS).

• List of individual pollutants and commonly reported individual pollutants in groups (aq-ei4-32)

Efforts are made to avoid the same emission being counted twice. Emissions data for point sources are shown for various chemical groups; detailed chemical-specific emissions can be obtained by contacting the MPCA.

Recommendations for reporting data for specific groups of compounds are summarized below in a hierarchy of the most preferred method to the least preferred method. For pollutant groups, only one reporting strategy per group per process should be used. Simultaneous use of more than one reporting strategy (e.g., reporting both individual chromium compounds and total chromium for the same source) will result in double counting.

Metal and cyanide groups

1. Within a process, and for a given metal or cyanide group, separately report emissions of all individual metal or cyanide compounds [e.g., report emissions of arsenic trioxide (ARSENIC 03, CAS No. 1327-53-3) if the process only has one compound in a metal/cyanide group and it can be reported under that compound]. Do not report it under the group [e.g., arsenic (ARSENIC CAS No. 7440-38-2)]. All individual compounds should be reported as the mass of the total compounds, not just the metal within the compound.
2. Report only emissions of metal or cyanide within the compound. To estimate the amount of metal in a compound divide the mass of the metal in 1 mole of the compound by the compound's molar mass and multiply the result by 100. For example if you have 1 lb emissions of ARSENIC O3 CAS No. 127-53-3 and you wish to report only ARSENIC CAS No. 7440-38-2, (molar mass of ARSENIC is 149.84, and molar mass of ARSENIC O3 is 197.841 g/mole, therefore ARSENIC is (149.84/197.841)*100 = 75.74% of the compound. If you are emitting 1 lb of ARSENIC O3, the amount of ARSENIC reported would be 0.7574 lbs. Use PubMed (nih.gov) to determine the mass of a compound.
   • Chromium - Since there is widely varying toxicity, you need to separate chromium compounds into trivalent (CHROMIUM III, CAS No. 16065-83-1) and hexavalent chromium (CHROMIUM VI, CAS No. 18540-29-9) if possible. You may report emissions for CHROMIUM, CAS No. 7440-47-3 if you cannot separate emissions. If the emissions are reported for CHROMIUM, CAS No. 7440-47-3 the emissions will be allocated to CHROMIUM III and CHROMIUM VI based on generic information when the data are used.
   • Do not include metals or cyanide already reported using the more preferred method in number 1. For example, CHROMIUM III, CAS No. 16065-83-1 and CHROMIUM CAS No. 7440-47-3 cannot be reported under the same process. The e-Services website will give an error message if both are reported.

Dioxins/furans

Report mass emissions of the following 17 individual congeners of chlorinated dibenzodioxins (CDDs) and chlorinated dibenzofurans (CDFs).

Glycol ethers

1. Report emissions for individual glycol ethers. All individual glycol ethers are shown on the air toxics pollutant list. 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 the structural definition provided by EPA to determine if the chemical is a glycol ether. The definition is:
   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.
2. If you cannot report individual glycol ether emissions, report total emissions of glycol ethers as a group under pollutant code GLYCOL ETHRS. You should not report emissions of one pollutant under both the individual pollutant name and GLYCOL ETHRS. The e-services website will give an error message if both are reported.

Xylenes and cresols

1. Report emissions for individual xylene and cresol isomers. If you report emissions for individual isomers do not report any emissions for total xylenes (XYLENES ISO, CAS No. 1330-20-7) or total cresols (CRESOLS MX IS, CAS No. 1319-77-3) to avoid double counting.
2. If you cannot report individual emissions of xylenes or cresols, report total emissions of xylenes or cresols as a group under XYLENES ISO, CAS No. 1330-20-7 or CRESOLS MX IS, CAS No. 1319-77-3.

Polycyclic organic matter (POM)

Report emissions of as many individual POM compounds as possible. All POMs are shown on the air toxic pollutants list. If you cannot report individual emissions of POM, report total emissions of POM.

2023 emissions inventory updates

• EPA added 1-bromopropane CAS No. 106-94-5 (also known as 1-BP, n-propyl bromide, and nPB) to the list of Hazardous Air Pollutants (HAPs).
• EPA added a number of individual pollutants classified under the Polycyclic Organic Matter (POM) group. These pollutants were added to be consistent with all TRI listed chemicals and are shown on the air toxic pollutants list.
• EPA also added individual isomers of Lindane. In the past emissions from Lindane were only reportable under “Lindane (All isomers).” All isomers of Lindane are shown on the air toxic pollutants list. 
• EPA added salts and esters of 2,4-D (2,4-Dichlorophenoxy Acetic Acid (2,4-D)). All salts and esters of 2,4-D are shown on the air toxic pollutants list.
• MPCA added Chlorine Dioxide and Sulfuryl Fluoride to the list of reportable pollutants to be consistent with the EPA pollutant list. 
• MPCA added new PFAS pollutants to the air toxic pollutants list. 
• MPCA added some pollutants to the list of reportable pollutants because of potential inhalation risk. 

Lindane

1. Report emissions for individual lindane isomers. If you report emissions for individual isomers do not report any emissions for total Lindane (LINDANE ISO CAS No. 58-89-9) to avoid double counting.
2. If you cannot report individual emissions of Lindane, report total emissions of Lindane as a group under (LINDANE ISO CAS No. 58-89-9).

Per- and polyfluoroalkyl substances (PFAS)

For the 2023 emissions inventory year, MPCA added 428 PFAS pollutants to the list of reportable pollutants. As part of the PFAS Monitoring Plan, MPCA is asking approximately 160 facilities to report air emissions of 51 PFAS pollutants for the 2023 reporting year. These 51 PFAS pollutants can be identified in the air toxic pollutants list by filtering the ‘Notes for Group’ column for ‘PFAS Monitoring Plan, OTM-45’.

PFAS reporting expectations and references were emailed to the 160 affected facilities in December 2022. This recorded PFAS presentation (Nov. 2022) includes ways to identify possible sources of PFAS emissions and estimate the emissions. For assistance identifying PFAS compounds in the materials you use, refer to the fact sheet below.

• PFAS industrial uses: Search tool (gp3-09)
• Air emissions reporting - PFAS compound identification (aq-ei4-49)

The OTM-45 pollutants and several hundred additional PFAS pollutants will be available in e-Services for any Large or Registration Option D facility to report 2023 emissions. This includes all salts and ions of OTM-45 analytes and all PFAS compounds EPA included in the Emissions Inventory System (EIS) and Toxics Release Inventory (TRI). PFAS compounds can be identified in the air toxic pollutants list by filtering the ‘Pollutant Group’ column for ‘PFAS’.

There is no ‘PFAS’ pollutant group under which multiple PFAS can be reported for 2023. If you have individual PFAS compounds to report that are not in the air toxic pollutants list, email us for assistance. 

For questions about PFAS reporting, or if you would like to be included on the PFAS air emissions email list, contact Joe Miller.