Can USEPA-RAGS risk assessment methodology be applied to the Workplace?

Michael J. Sullivan, Ph.D., CIH, REACalifornia State University at

Northridge

Outline

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

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

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

USEPA Risk Assessment Process

Hazard x Exposure = Risk

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

USEPA Risk Assessment Process

Calculations slightly different for carcinogens vs. non-carcinogens

Based on assumption of non-threshold vs. threshold mechanisms of action

USEPA Risk Assessment Process

Carcinogenic risks is Incremental Lifetime Cancer Risk (ICLR)

Non-carcinogenic risk is Hazard Quotient (HQ)

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)

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)

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)

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)

USEPA Risk Assessment Process USEPA has published risk-based

concentrations: Regional Screening Levels – RSLs Residential soil Residential air Residential water Industrial soil Industrial air

http://www.epa.gov/region9/superfund/prg/

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

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)

PEL Process vs. USEPA Process PELs

Require consensus Enforcable Weighted towards workplace

epidemiology RSLs

Easy to calculate Not enforceable Weighted towards toxicology data

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

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

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

Conclusion

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

Contact Information

Michael J. Sullivan, Ph.D., CIH, READepartment of Environmental and

Occupational HealthCalifornia State University at Northridge18111 Nordhoff StreetNorthridge, CA 91330michael.sullivan@csun.edu