Hyperplasia of the lymphoepithelium of NALT in rats but not in mice upon 28-day exposure to 15ppm formaldehyde vapor

Abstract

perplasia of the lymphoepithelium of NALT in rats but not in mice upon 28-day exposure to 15 ppm formaldehyde vapor. Experimental and Toxicologic Pathology, Elsevier, 2010, 63 (1-2) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractTo investigate if local lymphoid tissues are a target of FA, nasopharynx-associated lymphoid tissues (NALT) and upper-respiratory tract-draining lymph nodes were examined in a 28-day inhalation study with FA vapor in Fischer-344 rats and B6C3F1 mice.Paraffin-embedded tissues were sectioned and stained with H&E or stained immunohistochemically for cell proliferation (BrdU incorporation).Light microscopy revealed simple hyperplasia of NALT lymphoepithelium of rats exposed to 15 ppm and an increased proliferation rate of the epithelial cells. Principal component (discriminant) analysis of rat NALT and lymph nodes data did not reveal other effects or effects at lower exposure levels. Mice tissues were not affected.It was concluded that hyperplasia of the lymphoepithelium of NALT of rats exposed to 15 ppm was the only distinct effect of FA vapor on local lymphoid tissues (NALT and lymph nodes) of Fischer-344 rats and B3C3F1 mice.

Is exposure to formaldehyde in air causally associated with leukemia?—A hypothesis-based weight-of-evidence analysis

“…Kuper et al (2009) examined the proliferative effect of formaldehyde on the NALT and local lymphnodes in F344 rats and B6C3F1 mice exposed to 0, 0.5, 1, 2, 6, 10, and 15 ppm formaldehyde for 28 days. The authors found an increased proliferation rate in the nasal epithelial cells and a slight to moderate simple hyperplasia of the NALT in rats exposed to 15 ppm but not at lower concentrations, and no increases were observed at any concentration in mice, suggesting that at concentrations of less than 15 ppm formaldehyde, sufficient levels of formaldehyde do not move beyond the nasal mucosa to the NALT to induce cell proliferation.…”