1. Can USEPA-RAGS risk assessment methodology be applied to the Workplace?
Michael J. Sullivan, Ph.D., CIH, REA
California State University at Northridge

2. Outline PEL-Setting Process USEPA Risk Assessment Process
Comparison of Processes
Comparison of Results
Recommendation

3. PEL-Setting Process OSHA must propose and promulgate the PEL
Input received from NIOSH in form or Recommended Exposure Level (REL)
Other OELs can be considered

4. PEL-Setting Process Over 600 PELs have been promulgated by OSHA
Both toxicology and epidemiology information considered in weight-of-evidence process
Process weighted towards use of worker epidemiology data

5. USEPA Risk Assessment Process
Hazard x Exposure = Risk

6. USEPA Risk Assessment Process
Over 700 chemicals in USEPA database
Both toxicology and epidemiology information considered in weight-of-evidence process
Process weighted towards use of toxicology data

7. USEPA Risk Assessment Process
Calculations slightly different for carcinogens vs. non-carcinogens
Based on assumption of non-threshold vs. threshold mechanisms of action

8. USEPA Risk Assessment Process
Carcinogenic risks is Incremental Lifetime Cancer Risk (ICLR)
Non-carcinogenic risk is Hazard Quotient (HQ)

9. USEPA Risk Assessment Process
Carcinogens
Hazard = Cancer Slope Factor (CSF) (units = 1/exposure units)
Exposure = Lifetime Average Daily Dose (LADD) (units = exposure units)
Hazard x Exposure = Risk (unitless)

10. USEPA Risk Assessment Process
Carcinogens
LADD = EPC x Exposure Parameters
EPC = Exposure Point Concentration (e.g., concentration in air – mg/m3)
mg/m3 x exposure parameters x CSF = ILCR
mg/m3 = ILCR/(exposure parameters x CSF)
mg/m3 = Risk-based worker conc. (RBWC)

11. USEPA Risk Assessment Process
Non-Carcinogens
Hazard = Reference Concentration (RfC) (units = mg/m3)
Exposure = Average Daily Dose (ADD) (units = mg/m3)
1/Hazard x Exposure = Risk (unitless)

12. USEPA Risk Assessment Process
Non-Carcinogens
Exposure = EPC x Exposure Parameters
EPC = Exposure Point Concentration (e.g., concentration in air – mg/m3)
mg/m3 x exposure parameters x 1/RfC = HQ
mg/m3 = (HQ x RfC)/exposure parameters
mg/m3 = Risk-based Worker Conc. (RBWC)

13. USEPA Risk Assessment Process
USEPA has published risk-based concentrations: Regional Screening Levels – RSLs
Residential soil
Residential air
Residential water
Industrial soil
Industrial air

14. USEPA Risk Assessment Process
USEPA Industrial Air RSLs based on:
ILCR = 1 x 10-6
HQ = 1.0
Exposure Parameters
25 years
250 days/year
8 hours/day
70 kg body weight

15. USEPA Risk Assessment Process
USEPA RSLs (306)
127 for carcinogenic chemicals
134 for non-carcinogenic chemicals
45 for both C and NC chemicals
(706 total chemicals on EPA RSL list)

16. PEL Process vs. USEPA Process
PELs
Require consensus
Enforcable
Weighted towards workplace epidemiology
RSLs
Easy to calculate
Not enforceable
Weighted towards toxicology data

17. PEL Process vs. USEPA Process
Comparisons of PELs vs. RSLs for Selected Carcinogenic Chemicals
All PELs are higher than RSLs
Difference ranges from 100-fold to 50,000 fold
A 100 to 1,000-fold adjustment needed in RSLs to be roughly comparable

18. PEL Process vs. USEPA Process
Comparisons of PELs vs. RSLs for Selected Non-Carcinogenic Chemicals
All PELs are higher than RSLs
Difference ranges from 20-fold to 1,500- fold
A 10 to 100-fold adjustment needed in RSLs to be roughly comparable

19. Recommendation The PEL process is appropriate for protecting workers
Use adjusted USEPA RSLs (USEPA process) for new chemicals
Use the PEL process to approve or replace any USEPA RSLs with new PELs

20. Conclusion
The combined use of the PELs and RSLs can effectively protect worker health

21. Contact Information
Michael J. Sullivan, Ph.D., CIH, REA
Department of Environmental and Occupational Health
California State University at Northridge
18111 Nordhoff Street
Northridge, CA