Skip to main content
U.S. flag

An official website of the United States government

Here’s how you know

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

HTTPS

Secure .gov websites use HTTPS
A lock (LockA locked padlock) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

    • Environmental Topics
    • Air
    • Bed Bugs
    • Chemicals and Toxics
    • Climate Change
    • Emergency Response
    • Environmental Information by Location
    • Environmental Justice
    • Greener Living
    • Health
    • Land, Waste, and Cleanup
    • Lead
    • Mold
    • Pesticides
    • Radon
    • Science Topics
    • Water Topics
    • A-Z Topic Index
    • Laws & Regulations
    • By Business Sector
    • By Topic
    • Compliance
    • Enforcement
    • Guidance
    • Laws and Executive Orders
    • Regulations
    • Report a Violation
    • Environmental Violations
    • Fraud, Waste or Abuse
    • About EPA
    • Our Mission and What We Do
    • EPA Administrator
    • Headquarters Offices
    • Regional Offices
    • Labs and Research Centers
    • Planning, Budget, and Results
    • Organization Chart
    • EPA History
    • Staff Directory
Risk Assessment
Contact Us

Recommended Use of Body Weight 3/4 as the Default Method in Derivation of the Oral Reference Dose

Related Documents
  • 2005 Cancer Guidelines
  • Methods for Derivation of Inhalation Reference Concentrations and Application of Inhalation Dosimetry
  • Methods for Identifying a Default Cross-Species Scaling Factor (Rhomsberg, 2004)

Recommended Use of body weight ¾ as the Default Method in Derivation of the Oral Reference Dose presents body weight ¾ as the default methodology for interspecies dosimetric extrapolation for use in toxicological studies using animal data to assess effects on humans. The document lays out the scientific rationale for such an approach, the modifications to the application of interspecies uncertainty factors and provides the methods for computing the Dosimetric Adjustment Factor to determine the human equivalent dose. This document has undergone both internal (within EPA) and external peer review and public comment. The final document reflects the comments submitted through the review process.

Historically, EPA has applied a direct cross-species extrapolation based on body weight (body weight 1/1) for noncancer endpoints while applying a body weight ¾ extrapolation for cancer endpoints. By modifying the scaling to body weight ¾ for noncancer endpoints this document harmonizes the default methodology for assessing risks for cancer and noncancer endpoints.

Federal Register Notice

  • Federal Register, Friday, Jun 5, 1992, Draft Report. A Cross-Species Scaling Factor for Carcinogen Risk Assessment Based on Equivalence of mg/kg ¾ Day (PDF)(24 pp, 1.8 MB, About PDF)
  • Federal Register, Friday, Feb 25, 2011, Notice of Availability; Recommended Use of Body Weight3∕4 as the Default Method in Derivation of the Oral Reference Dose
     

Document Details and Links

  • External Peer Review Draft

This document promotes the use of body weight ¾ as a default method to convert data between species for both categories of endpoints. A hierarchy of methods for inter-species scaling is presented along with the rationale for selection of the scaling factor and guidance on how to conduct the conversion.

  • Recommended Use of Body Weight 3/4 as the Default Method in Derivation of the Oral Reference Dose (pdf) (466.69 KB, February 2011, 100-R11-00)
  • Summary Report of the Peer Review Teleconference on Harmonization in Interspecies Extrapolation: Use of BW3/4 as Default Method in Derivation of the Oral RfD (pdf) (1.52 MB, August 24, 2006)
  • Risk Assessment Home
  • About Risk Assessment
  • Risk Recent Additions
  • Human Health Risk Assessment
  • Ecological Risk Assessment
  • Risk Assessment Guidance
  • Risk Tools and Databases
  • Risk Management
  • Superfund Risk Assessment
  • Where you live
Contact Us to ask a question, provide feedback, or report a problem.
Last updated on June 22, 2022
United States Environmental Protection Agency

Discover.

  • Accessibility Statement
  • Budget & Performance
  • Contracting
  • EPA www Web Snapshot
  • Grants
  • No FEAR Act Data
  • Plain Writing
  • Privacy
  • Privacy and Security Notice

Connect.

  • Data.gov
  • Inspector General
  • Jobs
  • Newsroom
  • Open Government
  • Regulations.gov
  • Subscribe
  • USA.gov
  • White House

Ask.

  • Contact EPA
  • EPA Disclaimers
  • Hotlines
  • FOIA Requests
  • Frequent Questions

Follow.