The German Ad-hoc Working Group on Indoor Guidelines of the Indoor Air Hygiene Committee and the States' Supreme Health Authorities is issuing indoor air guide values to protect public health. No suitable human studies are available for health evaluation of acetaldehyde in indoor air. In a well-documented subchronic inhalation animal study with rats assessed as reliable, local irritation effects were observed in nasal epithelia, most prominently in the olfactory epithelium with loss of olfactory neuronal cells. This study leads to a LOAEC of 48 mg acetaldehyde/m(3) for continuous exposure for the endpoint nasal epithelium degeneration. By applying an interspecies factor of 1, a factor of 10 for interindividual variability, and a factor of 2 to account for the higher respiratory rate of children compared to adults, a health hazard guide value (RW II) of 1 mg acetaldehyde/m(3) is obtained. A health precaution guide value (RW I) of 0.1 mg acetaldehyde/m(3) is recommended.
