Formaldehyde
or plant material have not been studied.
Air
Formaldehyde is removed from the atmosphere by direct photolysis and oxidation by
photochemically produced hydroxyl radicals. Formaldehyde absorbs ultraviolet (UV) radiation at
wavelengths of 360 nm and longer; therefore, it is capable of photolyzing in sunlight. A half-life of
6 hours has been measured for photolysis in simulated sunlight. There are two photolytic pathways,
one producing H2 and CO, and the other producing H and HCO radicals. When the rates of these
reactions are combined with estimates of actinic irradiance, the predicted half-life of formaldehyde
due to photolysis in the lower atmosphere is 1.6 hours at a solar zenith angle of 40 degrees. Based
on its rate of reaction with photochemically produced hydroxyl radicals, formaldehyde has a
predicted half-life of approximately 19 hours in clean air and about half that time in polluted air.
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