Toxicity reference values (TRVs) for force health protection: Gap identification and TRV prediction

Area of Science:

• Occupational health
• Environmental toxicology
• Risk assessment

Background:

• The U.S. Air Force's Force Health Protection (FHP) program requires reliable exposure limits for warfighter readiness.
• Limited data and lack of authoritative toxicity reference values (TRVs) create significant gaps in assessing occupational exposures.
• Existing challenges necessitate the development of novel strategies for establishing health-protective exposure guidelines.

Purpose of the Study:

• To address the lack of authoritative toxicity reference values (TRVs) for substances encountered by U.S. Air Force (USAF) personnel.
• To integrate multiple approaches for generating health-protective exposure guidelines, specifically Operational Exposure Limits (OpELs).
• To identify and develop provisional OpELs when TRVs are unavailable.

Main Methods:

• Identification of 467 chemicals of interest for USAF FHP.
• Synthesis of multiple TRVs to derive OpELs.
• Implementation of straightforward TRV estimation approaches: Tier 1 Occupational Exposure Bands, cheminformatics (multiple linear regression, nearest-neighbor), and empirical adjustment of short-term TRVs.

Main Results:

• Rodent bioassay-derived Derived No Effect Levels (DNELs) were available for only 19 out of 84 substances with occupational TRV gaps.
• Several occupational TRV estimation methods were found to be readily implementable.
• Strategies were developed for identifying and creating provisional OpELs.

Conclusions:

• The study presents integrated approaches to bridge TRV gaps for USAF FHP.
• Developed methods offer practical solutions for risk assessors facing similar data limitations.
• These strategies enhance the ability to establish health-protective exposure guidelines for USAF personnel.