Criteria Pollutants

Project Proposer

Spreadsheet compares AAQS to “High first High” modeled concentrations.  This has typically been required for air toxics evaluations.

Provides additional information when hazard indexes are near one. 

PM_2.5

Project proposer

Updated guidance on PM_2.5 is now available allowing for direct PM_2.5 emissions to be considered in the AERA.

Estimating PM_2.5 Emissions for AERA’s

Mercury

Project proposer, MPCA EAO staff, MPCA mercury coordinator

Project proposers for sources identified in MPCA’s guidelines for new expanding sources of mercury air emissions must identify mercury inputs to and environmental releases from their facility/processes.  If fishable water bodies are within a 3 km radius of the facility (when stacks are < 100 meters), information submitted by proposer will be weighed to decide whether a focused analysis should be conducted to assess risks from consuming fish.

Over 80% of lakes assessed in Minnesota are considered impaired due to mercury contamination; consumption of mercury-contaminated fish can be harmful to people and wildlife. 

Surrogate health benchmarks as Risk Drivers

Project proposer,
MPCA EAO,
MDH

Surrogates are labeled in the RASS.  Project proposer may seek to further refine or speciated composition of mixtures with surrogates to apply IHB more selectively.  MDH may develop IHB for the mixture (e.g., MDH may recommend using IHBs for other petroleum mixtures in Total Petroleum Hydrocarbon guide). 

Use of surrogates to evaluate mixtures provides a rapid method of assessing emissions, and allows resources to be focused where necessary (only on potential risk drivers). Use of surrogates may help identify chemicals for which MDH could develop new IHBs.

Sensitizers

MPCA EAO staff

Chemicals in this category are noted in the RASS (RiskCalcs and Chem wo IHB pages).  May be considered along with quantitative information. 

Provides potentially important information to public (previously sensitized individuals may benefit from this information). 

Developmental Toxicants

MPCA EAO staff

Chemicals are labeled in RASS if they are developmental toxicants. The acute IHB for these chemicals are “ceiling values”, and EO staff note if these chemicals are predicted to exceed its IHB in the analysis.  

Developmental effects are serious and irreversible; acute benchmarks should be considered not-to-be exceeded ceiling concentrations since exposures to concentrations above the HRV/REL will increase the likelihood of damage. 

Chemicals lacking health benchmarks

MPCA EAO  staff, MDH

EO staff review list of chemicals emitted (emissions not quantified).  Using professional judgment/new information, EO and /or MDH staff may indicate a significant issue. 

MPCA is responsible for environmental protection, and needs to leave open the door for unforeseen chemical issues that may arise.  These chemicals will have evidence of potentially significant risk. 

Emergency Internal Combustion Engines

Project proposer

Project proposer provides information on AERA-04 (AERA Emergency Internal Combustion Engines). 

NOx emissions can show elevated acute hazard indices from internal combustion engines (including natural gas); short-term exposure to NOx at high concentrations can trigger asthma attacks in pre-disposed individuals.

Percent Mass Assessed

Project proposer

Project proposer inputs mass of HAPs and VOCs emitted from the facility into RASS, which automatically calculates percent of VOCs assessed.

Aids in elucidating completeness of quantitative risk estimates. If a very small percent of toxics mass emitted is assessed, qualitative factors may become more important to MPCA’s preliminary determination. Project proposer may seek MPCA guidance on what additional effort may be needed to further evaluate toxics, or more effort to reduce exposure may be appropriate.

Accidental Releases

MPCA EAO  Staff

MPCA staff query the Incident Management System to generate a list of facility reports of startup, shutdown and malfunction events from last 5 years. This is merely a report of incidence, not a quantification of emissions.  If applicable, this will be answered in the AERA Impact Analysis Form

Release represents exposure to some unknown level of risk.   Frequent releases indicate an operation that may be more likely to have future releases that are not being considered in the risk evaluation.  Especially important if developmental toxicants with ceiling concentrations are emitted.  Frequent breakdowns could be brought to the attention of the project proposer for explanation, and whether it’s being fixed in project proposal.

State and federal requirements

Project proposer, MPCA permitting staff

MPCA reviews project proposer’s analysis of whether emissions unit has an applicable standard.  MPCA permitting staff may also provide guidance on whether more effective control measures are available.

If an emissions unit does not have an applicable standard, or the standard appears to be insufficient, the project proposer prepares an analysis of technical, economic feasibility of additional pollution control equipment.

Toxicity Endpoints

Project proposer,
MPCA EAO staff

If HI is above one, MPCA may consider if the HI should be divided into target organ-specific Hazard Indexes.  Project proposer must seek guidance from MPCA EAO before staff will accept and review endpoint derivation.  Future guidance documents will provide more direct instruction.

 Calculating hazard indices by endpoint is appropriate but is a more refined analysis than initial screening

Conservativeness of Quantitative Assessment

MPCA EAO  staff

Environmental Outcomes staff will prepare a subjective assessment as to the overall conservativeness of the submittal.  Factors considered can include emissions estimates, dispersion modeling, toxicity assessment, other.  

Provides for interpreting the meaning of results and potential for impacts.

Monitored Ambient Air

MPCA EAO staff

Environmental Outcomes staff will be notified and asked for: maximum and average criteria pollutant and air toxic concentrations from monitors. A standard report will be produced of all pollutant concentrations monitored at representative station(s).  Some professional judgment will be used.

This information may be requested by the public (or perhaps already known by the public if the pollutant is a common one, e.g., benzene).  Important information for MPCA to consider if pre-existing concentrations of chemicals proposed to be emitted are already at levels of concern.