Introduction
The middle tab contains interactive tools for conducting Tier 1, 2, and 3 Health Risk Assessments (HRA) in support of Rules 1401, 1401.1, and 212; CEQA; permitting; and any other South Coast AQMD HRA requirements.
AERMOD- ready meteorological data files have been processed for 29 locations and can be downloaded from the rightmost tab
The rightmost tab also contains:
Wind roses at all meteorological sites
Background concentrations of criteria pollutants measured at 38 sites
Hourly background ozone data at 14 sites, during the same calendar years where the co-located or nearest meteorological station satisfied quality control criteria.
More details on the development and use of these meteorological data files are available here
Conducting Screening Health Risk Assessments (middle tab)
When using this HRA Tool, the user must first select the permit deemed complete date at the top of the screen. For previously-submitted permit applications, this is the date the permit application was deemed complete. For new permit applications and all other uses, please select the date of analysis or a future date. For permit applications deemed complete before November 1, 2024, please refer to the previous versions of the Risk Assessment Procedures and the corresponding Permit Application Packages for the screening tables to use.
The user can also select whether the list of Toxic Air Contaminants (TACs) analyzed should be limited to those in Rule 1401. For permit applications, select Yes. For CEQA, select No- this would include all TACs in the OEHHA/CARB consolidated list. Note that the dispersion factor tables (referred to as \(\chi\)/Q tables in previous Attachments to the Risk Assessment Procedures) for Tier 1 and 2 HRAs and the list of TACs analyzed pursuant to Rule 1401 for Tier 1, 2 and 3 HRAs will be affected by the date selected. The dispersion factor tables are updated periodically based on updates to meteorological data and the list of TACs are updated concurrent with amendments to Rule 1401. However, according to the Risk Assessment Procedures, the most updated health values are used in the calculation of health risks.
For Tier 1 HRAs, the user selects one or more TACs, enters the TAC emission rates and the Pollutant (or Application) Screening Index is calculated at downwind distances of 25m, 50m, and 100m. This is based on worst- case dispersion from a non-buoyant point source anywhere within South Coast AQMD’s jurisdiction.
For Tier 2 HRAs, the user selects the source type, source characteristics (i.e. building area, equipment rating, stack height, etc.), project location (click on the most representative meteorological site), and enters the TAC emission rates and various receptor distances. The HRA tool calculates the Maximum Individual Cancer Risk (MICR), Hazard Indices and Cancer Burden, as applicable. This is based on precomputed, conservative AERMOD simulations using the selected meteorological data, scaled by emission rates with impacts interpolated to the given distances.
For Tier 3 HRAs, the user must first run an air dispersion
model such as AERSCREEN outside of the HRA Tool to determine the TAC
concentrations at receptors of interest. The concentrations are then
entered into the HRA Tool to calculate health risks. The user will need
to justify source characteristics and model configuration used.
More information on South Coast AQMD’s Risk Assessment Procedures is available here.
Color Coded HRA Outputs
Green: MICR < 1; Hazard Quotient/ Index < 1; PSI/ ASI <= 1 or Cancer Burden < 0.5
Yellow: MICR 1- 10; Hazard Quotient/ Index => 1; PSI/ ASI >= 1 or Cancer Burden => 0.5
Orange: MICR > 10
Questions?
Please contact the Senior Meteorologist
Click on sites to obtain AERMOD- ready meteorological data files