Formaldehyde
Inhalation of concentrations of 10 ppm (12
mg/m 3 ) or above leads to clear increases in nasal tumor incidence in rats. Marked non- neoplastic
pathological lesions of the nasal cavity were present at tumorigenic concentrations. In contrast, no
significant numbers of tumors were seen in mice and Syrian hamsters following chronic exposure to
concentrations up to 14.3 or 30 ppm (17 - 36 mg/m 3 ), respectively.
These clear species differences appear to be related, in part, to the local dosimetry and disposition of
formaldehyde in nasal tissues. For example, mice possess the capacity to minimize inhalation of
irritating substances more efficiently than rats through a reflex depression of respiratory rate.
Studies in humans
The finding of nasal tumors in rodents exposed to high levels of airborne formaldehyde in the early
1980s led to a concern for cancer effects in occupationally exposed workers. There are now more
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