Repeated dose inhalation developmental toxicity study in rats exposed to cellulose insulation with boric acid additive

Inhal Toxicol. Nov-Dec 2018;30(13-14):542-552. doi: 10.1080/08958378.2019.1576806. Epub 2019 Mar 4.


Cellulose insulation (CI), a common building material, is a mixture of cellulose fibers and borates. Borates are approximately 20% of the product weight and act as a flame retardant. Given possible exposure to workers and consumers, an inhalation toxicity study was conducted following Organization for Economic Co-operation and Development (OECD) 414 for Prenatal Development Toxicity to evaluate if CI is a developmental toxicant. Pregnant female rats were exposed by nose-only inhalation to CI aerosols containing 20% boric acid for six h/day, from gestational day (GD) 6-19, and fetuses were evaluated for developmental parameters. Respirable CI was produced by grinding to produce respirable particles (MMAD 2.7-2.9 µm, geometric standard deviations (GSD) 1.9-2.6), which were then aerosolized. Target air concentrations were 15, 90, and 270 mg CI/m3. Controls were exposed to air only. Slight body weight reductions (average decrease <7% vs. control) were observed in male and female GD 20 fetuses in the mid and high dose groups. No embryo/fetal developmental toxicity or alterations in any other measured variable were reported at any dose. The no observed adverse effect level (NOAEL) for developmental outcomes was 270 mg/m3.

Keywords: Boric acid; cellulose insulation; developmental toxicity; particulates; rats; respiratory toxicity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Inhalation
  • Animals
  • Boric Acids / toxicity*
  • Cellulose / toxicity*
  • Construction Materials / toxicity*
  • Female
  • Fetus / drug effects
  • Male
  • Maternal-Fetal Exchange
  • No-Observed-Adverse-Effect Level
  • Pregnancy
  • Rats, Sprague-Dawley
  • Toxicity Tests


  • Boric Acids
  • Cellulose
  • boric acid