Abstract
The relative in vitro and in vivo toxicity of several types of manufactured fibrous glass insulation and crocidolite asbestos was investigated to aid in selection of a suitable glass fiber for subsequent use in inhalation exposures. The in vitro cytotoxicity to pulmonary alveolar macrophages of small glass fibers from microfiber insulation (count median diameter (CMD) ∼0.1–0.2 µm) was greater than that of the larger fibers from household insulation (CMD ∼2.4 µm). To screen for in vivo pulmonary toxicity, 2–21 mg of glass or asbestos fibers were administered in divided doses to male Syrian hamsters by intratracheal instillation. Animals were sacrificed at 1,3.5 and 11 months following initial administration of material. One type of glass microfiber [count median diameter (CMD) ∼0.1 µm] caused deaths from pulmonary edema at early times after instillation. High levels of asbestos, a second glass microfiber (CMD ∼0.2 µm) and one type of household insulation fiber (CMD 2.3 µm) all resulted in increases in total collagen and mild pulmonary fibrosis at later times after instillation, although microfiber insulation produced a greater response than household insulation. Asbestos insulation produced the greatest response. A five-day inhalation exposure to a high level of glass microfibers deposited in lung<10 percent of the lowest instilled amount which elicited indications of lung injury. This amount did not produce significant biological changes at 1 to 12 months after exposure.