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Environmental fate & pathways

Biodegradation in water: screening tests

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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. However this substance has been estimated as readily biodegradable in an OECD test.
Finally, 4-chloro-benzotrichloride is considered as readily biodegradable in water.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Two studies are available on ready biodegradability and one on the inherent biodegradability of 4-chloro-benzotrichloride.

In one insufficiently described study report (Muller 2001), the test substance was assessed as readily biodegradable.

In the study of Mendel (2002), the authors assessed the ready biodegradability and the biodegradability with adapted bacteria of 4 -chloro-benzoic acid (CAS n° 74-11-3) and was performed in accordance with the later published guideline OECD 301D (Ready Biodegradability - Closed bottle test). This substance is considered as a surrogate of 4-chloro-benzotrichloride as this former degrades in water into HCl and 4 -chloro-benzoic acid.

The concentrations of test substance used were 2.4, 8.0, 24 and 80 mg/L. During the testing period the biodegradation was followed based on the reduction of dissolved oxygen. The degree of biodegradation was calculated by the amount of oxygen taken up by the micro-organisms under these testing conditions (corrected with the uptake of the blank inoculum) and expressed as a percentage of the theoretical oxygen demand (ThOD). Furthermore also an inoculum blank, procedure control and emulsifier W control were included.

At concentrations of p-chlorobenzoic acid of 8 mg/L and higher toxic effects were observed after 20 days (without adaptation) and after 10 days (with adaptation). Furthermore, the dissolved oxygen was emaciated with the adapted inoculum at concentrations of 24 and 80 mg/L of test substance after 10 days and at concentrations of 8 mg/L and greater after 20 days.

The percentage of degradation of p-chlorobenzoic acid, concentration 2.4 mg/L, with the non-adapted inoculum was 0, 0 and 72.7% after 5, 10 and 20 days respectively, thus confirming the 10 -day window. Consequently the test substance can be classified as readily biodegradable.

In an inherent biodegradability test (Voelskow 2009), the authors tested an hydrolyzed solution of 4 -chloro-benzotrichloride (CAS n° 5216 -25 -1) under aerobic conditions according to DIN 38 412 Part 25, which is similar to the OECD Guideline 302B (Inherent Biodegradability: Zahn-Wellens/ EVPA Test). As an inoculum, non adapted activated industrial sludge was used and exposed to 821.2 mg/L of 4 -chloro-benzotrichloride. In total the DOC removal in three vessels was followed during 21 days. One vessel contained the test substance and inoculum (start concentration 821.2 mg/L test material), a second vessel contained inoculum alone, and a third contained reference compound and inoculum.

Under the test conditions biodegradation of the reference substancediethylene glycol wasmore than 80% after only 6 days and for the test substance a biodegradation was observedabove 70%. Thus, at this level of information the test substance can be considered as inherently biodegradable.

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 biodegradability in water. Hence the study of Mendel has been considered as the key study.

Since this substance has been estimated as readily biodegradable in an OECD test, 4-chloro-benzotrichloride is considered as readily biodegradable in water.