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Environmental fate & pathways

Phototransformation in water

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Description of key information

Information about the photolysis in water of chloroform are available from studies that have to be rated as not valid. Evidence exists that photolysis of chloroform in water in many cases is not a relevant degradation process and no photolysis of chloroform in water is taken into account.

Key value for chemical safety assessment

Half-life in water:
25 d

Additional information

A study carried out to measure the hydrolysis half-life of chloroform (Dilling et al. 1975) did not observe significant direct photolysis of chloroform in a 1-ppm solution exposed to sunlight for one year. However, the conditions during exposure were not standardised and the results of the study are considered as not reliable.

The study by Zepp et al. (1987) investigated the photo-production of hydrated electrons from dissolved organic matter (DOM) found in natural water bodies. They found that a significant yield of such electrons can be achieved by exposing solutions of DOM to steady-state laser or natural sunlight irradiation. It was predicted that chloroform and other electronegative organic pollutants of natural water bodies can react with hydrated electrons. The rate constant for this reaction with chloroform was calculated to be 0.0013 per hour. From this rate constant, a half-life of approximately 23 days can be calculated for indirect photolysis in water.

The available data indicate that chloroform may undergo relatively slow photodegradation in water in the presence of dissolved organic matter (DOM), but that photodegradation in water tends to be not significant in the absence of DOM.