Chloroform

Phototransformation in air

Description of key information

Available studies on the phototransformation of chloroform are not guideline-compliant. The available data indicate a rather slow dissipation of chloroform in air with an average half-life of approximately 70 days. The presence of smog may accelerate dissipation.

Key value for chemical safety assessment

Half-life in air:

70 d

Additional information

The studies of Pearson et al. (1975) and Singh et al. (1981) indicate rather long half-lives for photodegradation of chloroform in air of around 120 days. The half-life calculated by Singh et al. (1981) is for the reaction of chloroform with OH-radical being present in the atmosphere at a concentration of 1000,000 molecules per cm3. Klöpffer et al. (1988) studied the rate constant for reaction of chloroform with OH-radical in a standardised system by using a smog chamber equipped with 65 W Hg low pressure lamps. The reaction of atmospheric contaminants with OH-radical was described as the most important removal process from the atmosphere in their work. The concentration of OH-radical in the test atmosphere was considerably higher than the one assumed by Singh et al. (1981). Consequently, Klöpffer et al. (1988) found a higher rate constant for reaction of chloroform with OH-radical resulting in an estimated half-life for atmospheric chloroform of 26 days.