Hexabromocyclododecane (HBCD): A case study applying tiered testing for human health risk assessment.

Food Chem Toxicol

Mechanistic Studies Division, EHSRB, HECSB, Health Canada, Ottawa, ON, Canada. Electronic address:

Published: September 2019

Current global efforts are aiming to increase use of mechanistic information in regulatory testing. In tiered testing paradigms, in vitro, in silico, and in vivo studies are employed progressively to identify and classify health hazards, which are then compared against human equivalent doses. We used data from three companion papers on the brominated flame retardant hexabromocyclododecane (HBCD) to conduct a case study on tiered testing. We included ToxCastâ„¢ and in vitro-in vivo extrapolation (Tier 1), rat liver transcriptomic (Tier 2), and conventional rat (Tier 3) data. Bioactivity-exposure ratios (BERs) were derived by comparing human administered dose equivalents of the measured effects to Canadian exposure levels. Biological perturbations were highly aligned between Tiers 1/2, and consistent with apical effects in Tier 3. Tier 1 had the smallest BERs, and Tiers 2/3 were similar. The study demonstrates the promise of using physiologically-based pharmacokinetic modeling and mechanistic analyses in a tiered framework to identify pathways through which chemicals exert toxicological effects; however, they also point to some shortcomings associated with in vitro and in silico approaches. Additional case studies of chemicals from multiple classes are required to define optimal tiered screening procedures to reduce future in vivo requirements in health hazard assessments.

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.fct.2019.110581DOI Listing

Publication Analysis

Top Keywords

tiered testing
12
hexabromocyclododecane hbcd
8
case study
8
vitro silico
8
tiered
5
tier
5
hbcd case
4
study applying
4
applying tiered
4
testing
4

Similar Publications

Want AI Summaries of new PubMed Abstracts delivered to your In-box?

Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!