Trichloroacetyl chloride

Endpoint summary

Description of key information

No data on trichloroacetyl chloride is available for aquatic toxicity. A read-across approach with its degradation product in water (i.e. trichloroacetic acid) is applied and justified in the attached document of the endpoint study record.

Ecotoxicological data of trichloroacetic acid (TCA) are reported in the OECD SIDS Initial Assessment Report (2001). The lowest acute toxicity in valid test for fish and invertebrates has been selected for the present REACH registration dossier. It is reported that algae are very sensitive to TCA, but only results from non standardized tests were available. The strongest effects were recorded in a 14-day test with the species Chlorella pyrenoidosa and Chlorella mucosa (Bednarz, 1981).

More recently, the publication of Roberts et al. (2010) had the objective to clarify this ecotoxicological profile and to assess if a revision to the PNEC is required for TCA.

This publication summarises the situation of the ecotoxicological data of TCA as follows : the aquatic toxicity of TCA is reported with EC50 values (4h to 14d exposure duration) for a range of phytoplankton ranging from 300 µg/L to 2279 mg/L. The lowest available EC50 (14d) values were reported to be 300 and 460 µg/L for sodium TCA to Chlorella pyrenoidosa and Chlorella mucosa, respectively (Bednarz, 1981). Based on the concentration effect curves presented by Bednarz (1981), a 14d NOEC of 10 µg/L was determined for TCA (sodium salt) by Probit analysis, which corresponds to a NOEC of 8.7 µg/L (acid equivalent).The OECD SIDS (UNEP, 2000) risk assessment derived a predicted no effect concentration (PNEC) for aquatic systems for TCA (acid) of 0.17 µg/L based on an NOEC for algae of 8.7 µg/L and an assessment factor of 50.

A risk assessment for sodium hypochlorite has been carried out within the framework of council regulation (793/93/EEC) on existing chemicals. The risk assessment covers the environmental impact of both sodium hypochlorite and its major by-products. It has used an AF of 10 (based on the number of available aquatic toxicity studies) to derive a PNEC for TCA of 0.87 µg/L.

To clarify the ecotoxicological profile of TCA, Roberts et al. performed a series of algal toxicity tests according to OECD guidelines (OECD, 2006) using high purity test substance to derive EC50 and NOEC values for a range of freshwater algal species. The algal species used in this assessment included the strain used by Bednarz (1981), C. pyrenoidosa, two additional species of Chlorella (C. kessleri and C. vulgaris) and two other species commonly used to support the regulatory risk assessments, Pseudokirchneriella subcapitata and Scenedesmus subspicatus.

The results presented in the publication of Roberts et al. (2010) demonstrate that TCA is not as toxic as previously reported and that Chlorella are not the most sensitive species. No toxicity to TCA was observed in three species of Chlorella at concentrations up to 115 mg/L. They observed that the toxicity of TCA to P. subcapitata and S. subspicatus was over an order of magnitude greater than to three Chlorella species.

The most sensitive species reported in the OECD SIDS Initial Assessment Report has not been confirmed in a study performed according to a standard guideline. Therefore, for the present REACH dossier, the most sensitive species observed in the publication of Roberts et al. (2010) (i.e. P. subcapitata) has been selected as the key study and documented in an Endpoint Study Records. The 72-hour NOEC for growth rate was determined to be 3 mg/L. The 72-hour ErC50 value was determined to be 16.2 mg/L. Considering the difference of molecular weight between the source and the target substances, the results have been recalculated for trichloroacetyl chloride as a 72-hour NOEC of 3.3 mg/L and a 72-hour ErC50 of 18 mg/L.

It has to be noted that a publication on aquatic toxicity of TCA has been published more recently (Fisher et al., 2014). However, in this publication aquatic toxicity tests were performed without pH adjustment, and therefore effects due to low pH were observed. Consequently, this publication has not been retained for the assessment of TCA in the present REACH registration dossier. It should be noted that even with no adjustment of pH, acute EC50 and chronic NOEC values reported were all above the one obtained on P. subcapitataby Roberts et al. (2010). Therefore the approach applied in the present REACH registration dossier is a conservative approach. 

 

References:

Bednarz T., 1981. The effect of pesticides on the growth of green and blue-green algae cultures. Acta Hydrobiol.23,155–172.

Roberts Jayne F., Roger van Egmond, Oliver R. Price, 2010. Toxicity of haloacetic acids to freshwater algae. Ecotoxicology and Environmental Safety 73(2010)56–61.

UNEP (United Nations Environment Programme), 2000. Trichloroacetic acid, CAS No. 76-03-9. Screening information dataset (SIDS) for high production volume chemicals. United Nations inter-organisation programme for the sound management of chemicals, pp.164–211.