The effect of formaldehyde exposure upon the mononuclear phagocyte system of mice

The vapors of formaldehyde have been reported to represent a potential health hazard, resulting in an increased incidence of carcinomas of the nasal turbinates in experimental animals. To determine the potential role of alterations in the mononuclear phagocyte system (MPS) induced by inhalation of formaldehyde, we studied the systemic effects of exposure upon macrophages. Specifically, we examined the effects of formaldehyde exposure upon development of the MPS by use of an established system of quantitative objective markers, which characterizes and classifies populations of murine macrophages into several developmental stages. Exposure of mice to 15 ppm of formaldehyde for 6 hr daily for 3 weeks did not alter the number or impair the function of resident peritoneal macrophages, although this exposure increased (approximately twofold) competence for release of H2O2 from the macrophages. Furthermore, formaldehyde exposure did not alter the tumoricidal activation or differentiation of macrophages produced by the defined stimulant MVE-2. The data thus indicate that exposure of mice to formaldehyde can induce selective systemic alterations in the function of the MPS for H2O2 production, a change which has been shown in other studies to increase the frequency of mutagenesis.