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Environmental fate & pathways

Phototransformation in water

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Description of key information

Three studies of phototransformation in water are available for benoxacor. Based on the results of a guideline study, the calculated DT50 for photolysis benoxacor in water is less than 1 hour.

Key value for chemical safety assessment

Half-life in water:
1 h

Additional information

Three studies have been considered for the determination of photolysis of benoxacor under natural and artificial light. The first study (Carpenter, 1986) investigated the photodegradation of benoxacor in water, under natural sunlight and reported half lives ranging from 2.02 to 3.24 hours. This study was GLP compliant, was not performed to a standard guideline and was considered to be reliable with restrictions (Klimisch score 2).

The second study (Spare, 1988), which was performed according to the Pesticide Assessment Guidelines, Subdivision N, Chemistry: Environmental Fate, US EPA 1982 and EPA 540/9-82-021 guideline, provides DT50 values of 14 minutes under artificial light and 20 minutes under natural sunlight. The study was GLP compliant.

The third study (Abildt, 1993) investigated phototransformation of benoxacor in water under clear sky conditions. The study followed the UBA Test Guideline "Phototransformation of chemicals in water, Part A, Direct Phototransformation", was GLP compliant and was considered to be reliable without restrictions (Klimisch score 1). The DT50 for benoxacor ranged from 40 minutes to 52 minutes, at 40°N and 50°N respectively.

The more recent guideline study (Abildt, 1993) is considered to be the most reliable. Accordingly, a conservative DT50 value of 1 hour has been selected for use in the Chemical Safety Assessment.