Tetrachloroethylene

PBT assessment

PBT assessment: overall result

PBT status:

the substance is not PBT / vPvB

Justification:

Tetrachloroethylene is a monoconstituent substance with a purity of > 99.9%. There is no other constituent or impurity that requires assessment for PBT except for the main.

 

Persistence assessment:

The degradation of tetrachloroethylene by various abiotic and biotic processes has been examined in the relevant environmental media. 

Hydrolysis is not expected to be an important removal process for tetrachloroethylene. Half-lives in the range from 8.8 months to several million years have been reported (Dilling et al., 1975; Jeffers et al 1989). Photolysis is also unlikely to be a significant removal process for tetrachloroethylene in aquatic environments.

Tetrachloroethylene undergoes reactions with hydroxyl radicals in the atmosphere. The calculated half life of tetrachloroethylene due to this reaction is 50 days with an OH radical concentration of 1.5E6 OH/cm3 (AOPWIN, 2000), with an overall OH-rate constant of 8.05E-13cm3/molecule.sec. Tetrachloroethylene also reacts with ozone, nitrate radicals, hydroperoxy radicals, and chlorine atoms in the atmosphere but are thought to be insignificant atmospheric degradation processes. Overall, tetrachloroethylene is degraded in the atmosphere.

 

A number of studies have been reported on the biodegradation of tetrachloroethylene. The substance was not biodegraded under the stringent conditions of the modified shake flask closed bottle biodegradation test after 21 days (Mudder, 1982). Tetrachloroethylene does not appear to undergo aerobic biodegradation.

 

In contrast, data from simulation and screening tests demonstrated that tetrachloroethylene degrades well under specific anaerobic conditions. More than 99% of the tetrachloroethylene was dechlorinated in less than 200 days of incubation under either sulfate-reducing or methanogenic conditions in soil (Pavlostathis SG and Zhuang P, 1993). The conditions and inocula used appear to be important.

 

In view of the available information and the criteria summarized in Annex XIII, it is concluded that tetrachloroethylene meets the criteria for persistence (P and vP).

 

Bioaccumulation assessment:

Experimental BCF values are available for the assessment of tetrachloroethylene. The highest observed BCF in fish was 49 l/kg, based on the results of a flow-through exposure study with concentration monitoring. Based on these results, there is low potential for bioaccumulation and therefore tetrachloroethylene does not meet the B or vB criteria.

 

Toxicity assessment: 

The acute effect concentrations for all three trophic levels are much higher than the screening criterion of 0.1 mg/l. It can therefore be expected that tetrachloroethylene is not potentially toxic towards aquatic organisms. The chronic effect concentrations for invertebrates and algae were higher than the defined criterion of 0.01 mg/l. Further, tetrachloroethylene is not classified for CMR as category 1 under GHS nor as STOT RE cat 1 or 2. Therefore, tetrachloroethylene does not fulfill the T criteria.