Air Emissions Risk Analysis (AERA) — Guidance Updates: What's New Archives

A limited list of chemical toxicity value changes are found on the “Chemical Information” page. A complete list can be found in the "IHB Updates” worksheet in the Risk Assessment Screening Spreadsheet (RASS) or Q/CHI spreadsheet.

March 2012

In order to use the most up to date toxicity information, the toxicity values in the RASS from EPA’s Health Effects Assessment Summary Tables (HEAST) have been eliminated and Provisional Peer Reviewed Toxicity Values derived by EPA’s Superfund Health Risk Technical Support Center are now being used.  This was done in consultation with the Minnesota Department of Health.

June 2011

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.

September 2009

Multi-pathway Risk Analysis

Information describing additional exposure assumptions was added to the Multi-pathway Risk Analysis Web page. 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 with, and not replace, risk estimates based on reasonable maximum exposure assumptions that follow MPCA’s AERA guidance.

July 2009

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. Some of the factors that may be considered in evaluating the need for an AERA include the location of the facility, the types of receptors nearby and their distance from the facility, the type of facility and/or change, and the amount and types of emissions from the facility.

March 2009

Cumulative Air Emissions Risk Analysis

Cumulative Air Emissions Risk Analysis Guidance is now available on the Cumulative Air Emissions Risk Analysis Web page. 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%.

Please see the Mercury Guidance Web page for the latest version of the spreadsheet.

Multi-Pathway Screening Factors For Assessing Risks From Non-Inhalation Exposures To Air Pollutants

The RASS and Q/CHI spreadsheet have been updated with the new multimedia factors. An explanation of the development of these new multimedia factors (multi-pathway screening 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), which is available on the Multi-pathway Risk Analysis Web page.

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. All other pollutants with AP-42 values should be included quantitatively.

• 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

September 2007

Updated AERA Guide

The AERA Guide was updated in version 1.1 of the document to reflect policy changes and modifications to the AERA process that occurred since the original document was developed in 2004. This update did not present new information or require different methodologies but rather incorporated the updates that were posted on this website since the beginning of the AERA process and were not previously in the guide.

June 2007

Emissions from Utilizing Natural Gas as an Onsite Fuel Source

MPCA staff reviewed past practices of the onsite sources that should be included in the Risk Analysis Screening Spreadsheet (RASS) and concluded that emissions from utilizing natural gas as a fuel should also be quantified. If your facility utilizes natural gas as a fuel in boilers or other devices and you are completing an AERA, the combustion products and their emissions from natural gas need to be included in the RASS.

Several developments prompted a review of the exclusion of emissions when utilizing natural gas. These developments include the availability of information, improved tools for assessing health impacts, and the need to address the health impacts of natural gas combustion in a facility’s evaluation. Over the past year, several facilities have quantified these emissions and included them in their analysis and submittals to ensure a more complete quantification of estimated impacts. MPCA staff is also developing explicit guidance when assessing cumulative potential effects for the environmental review process.

A reminder regarding when to prepare an AERA

Recent changes to the EAW threshold from 100 tpy to 250 tpy for individual criteria pollutants won’t eliminate the need for an AERA. Proposers should still plan to complete an AERA if their facility’s potential to emit is >100 tpy for any individual pollutant.

January 2007

MPCA’s Mercury Risk Estimation Model now available

• The MPCA Mercury Risk Estimation Method (MMREM) is now available for assessing the incremental mercury risk associated with eating fish from water bodies near permitted or potentially permitted sources.  MMREM can be used to estimate the noncancer oral hazard quotients associated with fish tissue consumption based on increases in mercury deposition.

Alteration in Guidance for Estimating PM_2.5 Emission from AERAs

• As of March 31, 2006, US EPA no longer supports the PM Calculator Software. The PM Calculator is referenced in MPCA’s  Estimating PM_2.5 Emissions for AERAs (aq9-12) guidance for calculating filterable PM_2.5 emissions.  PM_2.5 emission factors are still available in EPA's WebFIRE database and AP-42 emission factor compilations.

August 2006

Ethanol Facilities:  Determination of Need for an Air Emissions Risk Analysis

• The Determination of Need for an Air Emissions Risk Analysis offers a checklist for an ethanol facility proposer to determine if this type of analysis is necessary in the planning and permitting process for an ethanol production facility.
• For additional information contact Heather Magee-Hill.

March 2006

Estimating PM_2.5 Emissions for AERAs

• The Estimating PM_2.5 Emissions for AERAs (aq9-12) amends the MPCA’s Air Emissions Risk Analysis (AERA) Guidance Version 1.0 dated March 2004 related to estimating PM_2.5 emissions and predicting ambient air impacts.  Specifically, section 2.6.1 “Criteria pollutants” and section 3.4.8 “PM_2.5” were revised as described in this guidance.
• For additional information see the AERA Emissions Web page.

Updated Guidance and Forms

• AERAs submitted after April 15, 2006 should incorporate the Emissions Estimating Guidance and updated forms.  A six month grace period will apply for forms and emissions guidance submitted after April 15, 2006.  However, using the updated MPCA materials may expedite the AERA process.

February 2006

Emissions Estimating Guidance For Use in an AERA

• MPCA Emissions Estimating Guidance For Use in an AERA (aq9-06) provides general guidance for preparing emission estimates for input into the risk analysis screening spreadsheet (RASS) of an Air Emissions Risk Analysis (AERA), and is to be viewed as a supplement to the MPCA’s AERA Guidance. It is the goal of the MPCA that emission estimates used in an AERA should be the most accurate estimate of emissions over the appropriate timeframe with a reasonable certainty that chemical emission rates are not underestimated, irrespective of the data source from which they are derived.
• For additional information see the AERA Emissions Web page.

January 2006

Buffer Distance

• MPCA altered buffer distances previously used in providing data in the Qualitative Analysis section of the AERA.

October 28, 2005

Ethanol Sector Specific Interim Exposure Values Guidance

• The Minnesota Department of Health (MDH) developed acute and chronic Ethanol Sector Specific Interim Exposure Values (ESSIEVs) for thirteen chemicals.  MDH considers the ESSIEVs sector specific for ethanol production facilities and cannot endorse the routine use of ESSIEVs for other types of facilities.

RASS

• The RASS was revised to incorporate the Ethanol Sector Specific values. The updated RASS requires that an SIC code be entered on the Emissions worksheet.
• An unlocked version of the RASS will no longer be available on the website. Facilities seeking to use an unlocked version will need to contact MPCA risk assessment staff listed at the bottom of this page.

July 2005

AERA Guidance Revision

• Effective July 2005: For proposed expansions to existing facilities requiring AERAs, project proposers will need to submit current facility emissions and total facility emissions after the proposed modification. At a minimum this will result in two RASS and the supporting documentation.
• For additional information and guidance on this policy please contact risk assessment staff listed below.

Risk Assessment staff

• Shelley Burman, Supervisor, 651-757-2255
• Mary Dymond, 651-757-2327
• Kristie Ellickson, 651-757-2336