The list below provides an overview of updates made to the AERA process and associated tools. For a complete record of updates made to the chemical toxicity values see the IHB updates section of the Risk Assessment Screening Spreadsheet (RASS).
Inhalation health benchmarks were updated in the RASS and Q/CHI spreadsheet tools. References to the MPCA Citizens' Board were removed from the AERA webpages. DISPERSE was removed from the list of recommended dispersion models.
The AERA guide and associated forms have been redesigned and updated to reflect improvements to the AERA process since the 2007 AERA Guide. The new AERA guide is web-based with a PDF version available for printing.
The RASS Multi-pathway Screening Factors were updated, the tool itself was simplified, and the health benchmarks were updated as of December 2014.
In March 2012, the RASS was updated using EPA’s Peer Reviewed Toxicity Values (PPRTV’s), replacing the values derived from EPA’s Health Effects Assessment Summary Tables (HEAST). This was done in consultation with the Minnesota Department of Health.
Guidance on “Who Needs an AERA?” has been changed. The default threshold for industrial facilities has been changed to coincide with environmental review program. The MPCA will continue to use its discretion in requesting proposers conduct an AERA for projects outside of this default.
Guidance for conducting cumulative air emissions risk analyses has been added to the AERA guidance document.
The AERA Forms were updated to reflect procedural changes that will allow the MPCA to determine if an air permit application is complete within 30 business days, with the goal of issuing the air permit in 150 calendar days. It is highly recommended that AERA materials be submitted for MPCA review prior to submitting an air permit so that site specific suggestions from the MPCA can be incorporated into the AERA.
An AERA with a refined analysis based on EPA’s Human Health Risk Assessment Protocol (e.g. IRAP) will require approval of a protocol (the new AERA-26 form) prior to submitting an air permit application. Proposers and consultants working on projects that may require an AERA should discuss their project with an MPCA supervisor or manager before beginning work on an AERA.
Multi-pathway Risk Analysis
Information describing additional exposure assumptions was added to the AERA guidance document. This additional set of assumptions describes the use of central tendency estimates for human exposure. The risk estimates using central tendency assumptions for human exposure should be presented in addition to, and not replace, risk estimates based on reasonable maximum exposure assumptions.
Change in AERA guidance: Who needs to complete an AERA?
Change in Default Thresholds for AERAs: The MPCA program managers have changed the default thresholds for conducting AERAs to coincide with environmental review thresholds. Proposals going through the environmental review process because a project meets thresholds identified in Minn. R. 4410.4300.subp.15 or Minn. R. 4410.4400 and the project increases air emissions of a single criteria pollutant by 250 tons per year or more need to conduct an AERA. However, the MPCA will continue to use its discretion in requesting proposers conduct an AERA for projects outside of this default. These cases generally encompass existing air emission sources that are the source of significant public interest or the specifics of a new facility or existing facility expansion indicate a need for further analysis prior to public notice.
Cumulative Air Emissions Risk Analysis
Cumulative Air Emissions Risk Analysis guidance is now available in the AERA guidance document. A cumulative air emissions risk analysis evaluates risks from multiple sources, on-site and off-site. On-site sources include point, area, and mobile sources associated with the existing facility and the proposed project. Off-site sources include nearby point, area, mobile sources and regional background. The air concentrations associated with these emissions are either generated from air dispersion modeling and/or ambient monitoring data. The degree to which air emissions are assessed for each source is dependent on the availability of modeling and monitoring data.
Updated Mercury Guidance
The January 2009 version of the MPCA’s Mercury Risk Estimation Model (MMREM) has been updated to reflect comments from independent reviewers. The fraction of the terrestrial watershed reaching the water body increased from 10% to 26%.
Multi-Pathway Screening Factors For Assessing Risks From Non-Inhalation Exposures To Air Pollutants
The RASS and Q/CHI spreadsheet have been updated with new multimedia factors. An explanation of the development of these new multimedia factors can be found in the paper Multi-Pathway Screening Factors For Assessing Risks From Non-Inhalation Exposures To Air Pollutants completed by Dr. Gregory Pratt and Mary Dymond of the MPCA. This study was published in the Journal of the Air and Waste Management Association (April 2009).
Updating Guidance For Estimating Emissions From Natural Gas Boilers
The following pollutants with E rated emission factors based on detection limits from AP-42 do not need to be included in quantitative emission estimates from natural gas fueled boilers because of the uncertainty associated with them. Instead, they should be discussed qualitatively.
- 56-49-5 3-Methylchloranthrene
- 57-97-6 7,12-Dimethylbenz(a)anthracene
- 83-32-9 Acenaphthene
- 203-96-8 Acenaphthylene
- 120-12-7 Anthracene
- 56-55-3 Benz(a)anthracene
- 50-32-8 Benzo(a)pyrene
- 205-99-2 Benzo(b)fluoranthene
- 191-24-2 Benzo(g,h,i)perylene
- 205-82-3 Benzo(k)fluoranthene
- 218-01-9 Chrysene
- 53-70-3 Dibenzo(a,h)anthracene
- 193-39-5 Indeno(1,2,3-cd)pyrene
- 7440-41-7 Beryllium
- 7782-49-2 Selenium