Trichloroethylene

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, industrial (adaptation not specified)

Details on inoculum:

1 drop of the inoculum was added per l of medium

Duration of test (contact time):

28 d

Initial conc.:

2 - 10 mg/L

Based on:

not specified

Parameter followed for biodegradation estimation:

O2 consumption

Key result

Parameter:

% degradation (O2 consumption)

Value:

19

Sampling time:

28 d

Details on results:

No further details given

Interpretation of results:

not readily biodegradable

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Remarks:

Accepted database

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Key result

Parameter:

% degradation (O2 consumption)

Value:

2.4

Sampling time:

28 d

Details on results:

Not readily biodegradable

Not readily biodegradable

Interpretation of results:

not readily biodegradable

Description of key information

Within a weight of evidence approach trichloroethylene was considered not readily biodegradable for further assessment.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Additional information

Various information is available for readily biodegradation testing of TCE, including studies with activated sludge as well as single culture baceteria. Within a weight of evidence approach the following two studies conducted with activated sludge as inoculum, have been identified as most reliable for assessing this endpoint. Under the stringent conditions of an OECD 301 D study only slight degradation of 19 % under aerobic condition was observed within the 28-day observation period of the study (Rott et al., 1982). Further in a study according to the OECD 301C guideline under aerobic condition a biodegradation rate of 2 % was reported (CSCL, 1992).

 

Further studies indicate a faster degradation rate of Trichlorethylene under specific conditions e.g. using anaerobic condition, specific adaped cultures as inoculum and/or in the presence of co-substrates.

However, for purpose of further assessment Trichlorethylene is considered to be not readily biodegradable.

 

This is agreement with EU risk assessment (2004) and recently published EPA draft risk assessment (2020).