Respiratory and metabolic response of rats and mice to formalin vapor

The irritant effect of repeated inhalation exposure to vapors of aqueous formalin (formaldehyde concentration, 15 ppm) in male Charles River CD rats and male C57BL6/F1 mice was determined. The data suggest that rats are relatively insensitive to this irritant while mice are substantially more sensitive, the latter showing a comparable reduction in tidal volume, but a greater decrease in respiratory rate and, as a consequence, minute volume. CO2 production, a reflection of total metabolism, as well as body temperature, were decreased to a greater extent in mice than in rats. The decreased minute ventilation and associated decrease in temperature, responses occurring to a greater extent in the mouse, may decrease both the net formaldehyde dose as well as the toxic actions of formaldehyde that are dependent on systemic metabolic activity.