EPA Time-Weighted Average Lead Risk Calculator

This calculator is currently in the beta stage of development - please report any bugs encountered to the RAIS Team. Thank you.


EPA Time-Weighted Average Lead Risk Calculator

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Time-Weighted Average Lead Risk Calculator

Geometric Blood Lead Equation (track-in on)

Geometric Blood Lead Equation (track-in off)

Probability (Risk) of Time-Weighted Geometric Mean Blood Lead Level Exceeding Blood Target Level Equation

Enter Target Inputs




Enter Soil and Dust Exposure Percentages


Enter DU Soil Inputs


TWA Inputs to IEUBK: Track-In ON


Relative Percent Contribution of Site and House Exposure


IEUBK Model Predicted Geomean Blood Lead PbB & Risk Estimate (% probability of exceeding the target PbB): Track-In ON


Notes
  1. The default Target PbB value of 5 μg/dL is based on TRW Lead Committee recommendations, with a suggested range of 3.5 to 10 μg/dL.
  2. All other IEUBK model variables are defaults in IEUBK model (v2.0 build 1.72).
  3. In the Geometric Blood Lead equation, 'S' is the combined soil and dust concentration. Calculated as a weighted average of site and home soil dust concentrations. If S exceeds 7776.4 then BLL is capped at 30.001. Otherwise, BLL is obtained via IEUBK interpolation with S.
  4. The EPC (Exposure Point Concentration) for lead during intermittent site exposure would be calculated as a time-weighted average of the site DU (Decision Unit) lead concentration and house DU (Decision Unit) soil lead concentration (see US EPA 2024)3.
  5. This calculator illustrates the impact of residential soil lead concentration on risk predictions (3.5 - 10 μg/dL) over a range of potential site concentrations for intermittent exposures, and calculates the relative contribution of site and residential soil lead intake for each combination of site and residential soil concentration.
  6. This calculator has two options: 'Track-In' on and 'Track-In' off. The check box is located in the top left, above the equation images. Checking the box assumes a contaminated site where lead has been tracked in from another source, such as tracking in lead-contaminated dust into your house via dirtied clothing. In contrast, unchecking the box refers to an a scenario where no dust is tracked to the second site. For a more technical overview, see the Geometric Blood Lead Equations at the top.
  7. Because the exposure of children to lead at other non-residential sites is in addition to their residential exposure, time weighting would typically be used to derive an input to the IEUBK model (see US EPA 2024)3. Note the exposure frequency and duration must be no less than one day per week for 13 consecutive weeks (or equivalent) (see US EPA 2024)3.
  8. This calculator is valid for soil lead concentrations greater than 25 mg/kg (whole numbers only). The 25 mg/kg value is taken from the lower range of soil lead background from the USGS analysis (see US EPA 2021)2.
  9. The table showing Relative Percent Contribution of Site and House Exposure is intended to inform risk management. See Sections 3.3 and 3.4 of US EPA 20243 for more information.

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