GUIDANCE FOR THE CALCU

CANCER AND NON-CANCER 

INHALATION EXPOSU

AN UPDATE

Michael Sivak, EPA Risk AsseConferenceMay 3, 2006
Topics

z Purpose of the documentz Project historyz Workgroup membersz Comparison of previous and upd

methodologies

z Example issues discussed by woz Next Steps
Purpose of Document

z To update existing Superfund guidance on 

cancer risk and non-cancer hazard from coexposures through the inhalation route (e.gA) to be consistent with current science coinhalation dosimetry.

z Document will endorse the use of the Refe

Concentration (RfC) and Inhalation Unit Risapproach to inhalation risk assessment insof Inhalation Reference Doses (RfDis) and 

Cancer Slope Factors (CSFis).

z Document will provide recommendations c

issues in inhalation risk assessment (e.g., extrapolation).
Project History

z October 1994 – EPA publishes “Methods for Derivation 

Reference Concentrations and Application of Inhalation 

z July 1996 & December 2002 – EPA publishes Soil Scr

documents implementing the RfC/IUR approach in deveSoil Screening Levels (SSLs) for volatile contaminants.

z September 2003 - EPA Workshop, “Inhalation Risk Ass

Superfund Focus.” Strawman document presented.

z Fall 2004 - Industrial Economics (IEc) updates Strawma

comments and discussion from workshop. Outline of ddocument prepared.

z Spring 2005 – Inhalation risk workgroup established. D

document prepared by IEc for distribution to EPA workg

z Summer 2005 – Draft guidance document distributed t

members. Bi-weekly conference calls begin to discuss 

z Spring 2006 – Bi-weekly workgroup meetings conclude

incorporate consensus decisions made by the group int
Workgroup Members

z Dave Crawford (OSWER/OSRTI)*z Michael Sivak (Region 2)*z Brenda Foos (OCHP)z Gary Foureman (ORD/NCEA)z Ann Johnson (OA/OPEI)z Deirdre Murphy (OAR/OAQPS)z Henry Schuver (OSWER/OSW)z John Stanek (ORD/NCEA)z Neil Stiber (ORD/OSP)z Timothy Taylor (OSWER/OSW)z John Whalan (ORD/NCEA)

z Sarah Levz Jennifer Hz Ofia Hodoz Kevin Koz Arunas Dz Cheryl Ovz Jeremy Joz Bob Bensz Susan Grz Daniel Strz Marcia Baz Tyra Gettz Henry Ro

* Co-chair

z Eric Rude
Previous Approach Compared 

Approach: CarcinogensPrevious Approach (RAGS, Part A):Chronic Daily Intake = CA x (IR/BW) x (ET x EF Cancer Risk = Intake x CSFiUpdated Approach (1994 Guidance):Exposure Concentration (EC) = (CA x ET x EF x Cancer Risk = EC x IURWhere: CA = concentration in air; IR = Inhalation Rate

= exposure time; EF = exposure frequency; ED = averaging time; CSFi = inhalation cancer slope fac

inhalation unit risk.
Previous Approach Compared 

Approach: Non-Carcinogens Previous Approach (RAGS, Part A):Chronic Daily Intake = CA x (IR/BW) x (ET x EF Hazard Quotient (HQ) = Intake/RfDiUpdated Approach (1994 Guidance):*Exposure Concentration (EC) = (CA x ET x EF x HQ = EC/RfCWhere: CA = concentration in air; IR = Inhalation Rate

= exposure time; EF = exposure frequency; ED = averaging time; RfDi = inhalation reference dose; a

concentration.

* = this example assumes a chronic exposure scenario
Example Issues Discussed by W

z Protectiveness of the updated approach for chi

subpopulations;

z Calculating cancer risks from high-level exposuz Characterizing inhalation exposure scenarios a

appropriate toxicity data;

z Identifying inhalation toxicity data for less-than z Use of route-to-route extrapolation;z Development of screening levels for inhalation z Aggregating risk across multiple exposure routez Calculating risk for occupational scenarios; andz Key uncertainties in the inhalation risk assessm
Protectiveness of the Updated 

for Children and Sensitive Subz Workgroup discussed comments raise

inhalation workshop about the protectupdated methodology for exposures tother susceptible subgroups. Commeconcerned that the risk equations do nadjustments for these groups.
Resolution

z Document will indicate that the 10-fold uncert

intra-species variability considered when deridesigned to address variation in susceptibility population. Document will also highlight consassumptions in the derivation of IURs. 

z Risk Characterization section will encourage 

describe sensitive populations or individuals wthat may exist at a site and discuss potential estimates for these groups.

z Appendix to the guidance document presents 

Human Equivalent Concentrations (HECs) cadefault parameters with HECs calculated usingroup-specific parameters. 
Route-to-Route Extrapola

z Workgroup addressed the issue 

not to use route-to-route extrapotoxicity data to generate an RfC contaminant lacking inhalation to
Resolution

z Guidance will recommend against performing 

extrapolation using default bodyweight and inparameters. Document will indicate potential with this approach.

z Guidance will recommend that risk assessor 

Superfund Health Risk Technical Support Ceassistance.

z If no alternate value is available, document re

performing a qualitative risk assessment, and issue in the uncertainty section of the risk ass
Next Steps

z First round of workgroup meetings complet

revising the draft guidance document, incoworkgroup recommendations.

z Early June 2006: Revised draft sent to wo

review.

z Late June 2006: Workgroup meetings to d

comments on draft; IEc to revise.

z August 2006: Revised draft document circ

broader internal EPA review.

z Late 2006: Document submitted for extern