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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

4-chloro-benzotrichloride is instantly degraded in water into 4-chloro-benzoic acid and hydrochloric acid. Furthermore, since this substance is used as an intermediate under strictly controlled conditions, hydrochloric acid is entirely removed from water by the on-site waste water treatment of the chemical plant. Thus only the surrogate 4-chloro-benzoic acid is of concern.
This latter substance has been tested

Key value for chemical safety assessment

EC50 for freshwater algae:
17.29 mg/L
EC10 or NOEC for freshwater algae:
0.57 mg/L

Additional information

Only toxicity to freshwater algaes has been tested.

In the study of Lee (2009), the authors tested the influence of 4-chlorobenzoic acid (CAS n° 74-11-3) on the final yield and growth rate ofPseudokirchneriella subcapitatausinga closed system algal toxicity test. Since 4-chlorobenzotrichloride reacts almost immediately in water forming 4-chlorobenzoic acid as one of the degradation products, 4-chlorobenzoic acid is considered a test surrogate.

The algal inoculum was transferred together with growth medium (US EPA OPPTS 850.5400, without EDTA) and test substance (unless control vessel) into BOD bottles. Based on a range finding study, six to seven concentrations, ranging from 0.5 to 123 were tested in triplicate and controls were also included.

The duration of the test was 48h and algae population density was determined using an electronic particle counter. A Probit analysis was used to determine the concentration–response relationship and the median effective concentration (EC50), while the one-tail Dunnett’s procedure was used to estimate the NOEC and LOEC values at 5% level of significance.

In these test conditions, EC50(48h) for final yield and growth rate were 6.42 mg/L and 17.29 mg/L respectively and the NOEC (48h) for both endpoints was 0.57 mg/L. Finally, 4-chlorobenzoic acid cannot be classified based on the CLP regulation (EC) N° 1272/2008 since the test duration was 48h instead of the required 72h or 96h. However the toxic levels observed during this test are applicable for the 4 -chlorobenzotrichloride.

Hence, provided the available information and that 4-chloro-benzotrichloride is instantly degraded in water into 4-chloro-benzoic acid and hydrochloric acid. Furthermore, that this substance is used as an intermediate under strictly controlled conditions, and that hydrochloric acid is entirely removed from water by the on-site waste water treatment of the chemical plant.

It has been decided that only the surrogate 4-chloro-benzoic acid is of concern regarding the endpoint on toxicity to aquatic algaes.

Thus the study of Lee (2009) has been chosen as the key study.