3,5-dichlorobenzoyl chloride

Toxicity to aquatic algae and cyanobacteria

Description of key information

The 72h-NOEC for growth rate inhibition was 9.7 mg/L. 

Key value for chemical safety assessment

EC50 for freshwater algae:

33 mg/L

EC10 or NOEC for freshwater algae:

9.7 mg/L

Additional information

The toxicity of the test material to the freshwater green alga Pseudokirchneriella subcapitata was investigated in accordance with the standardised guidelines OECD 201, EU Method C.3 and the OECD series on testing and assessment number 23 under GLP conditions. The study has been assigned a reliability score of 1 in line with the principles for assessing data quality as defined by Klimisch et al. (1997).

The test material was not completely soluble in test medium at the initial loading rate. A Water Soluble Fraction (WSF) was prepared at a loading rate of 100 mg/L and was used as the highest test concentration. Lower test concentrations were prepared by subsequent dilutions of the WSF in test medium.

A final test was performed based on the results of a preceding combined limit/range-finding test. Six exponentially growing algal cultures were exposed to an untreated control and three replicates per group were exposed to 10, 18, 32, 56 and 100 % of a WSF prepared at a loading rate of 100 mg/L. The initial algal cell density was 10⁴ cells/mL. The total exposure period was 72 hours and samples for analytical confirmation of actual exposure concentrations were taken at the start and at the end of the test period. The range tested based on average measured concentrations was 3.0, 5.2, 9.7, 17, and 31 mg/L.

Growth rates were in the range of the controls at the three lowest concentrations during the 72-hour test period, whereas the growth rates of algae exposed to concentrations from 17 and 31 mg/L were increasingly reduced. Statistically significant inhibition of growth rate was found at test concentrations of 5.2 mg/L and higher. As the exposure to concentrations of 9.7 mg/L and less did not cause more than 10 % inhibition of growth rates, they were considered biologically irrelevant.

Reduction of yield increased with increasing concentration of the test material at all concentrations, resulting in 91% reduction at 31 mg/L. Statistically significant reduction of yield was found at all test concentrations. As the exposure to concentrations of 3.0 mg/L did not cause more than 10 % inhibition of yield, this concentration was considered biologically irrelevant.

The study met the acceptability criteria prescribed by the study plan and was considered valid.

Under the conditions of the study, the 72 h EC50 for growth rate inhibition and yield inhibition were 33 mg/L (95 % CI 32 to 35 mg/L) and 15 mg/L (95 % CI 14 to 16 mg/L), respectively. The 72 h NOEC for growth rate inhibition and yield inhibition were 9.7 and 3.0 mg/L, respectively.