European Union Risk Assessment Report - PBT Assessment of Musk Xylene 5-TERT-BUTYL-2,4,6-TRINITRO-M-XYLENE - Addendum to the final report (2005) of the risk assessment

The report provides the PBT assessment of the substance 5 tert butyl 2,4,6 trinitro-m-xylene (musk xylene). It has been prepared by The Netherlands in the frame of Council Regulation (EEC) No. 793/93 on the evaluation and control of the risks of existing substances, following the principles for assessment of the risks to humans and the environment, laid down in Commission Regulation (EC) No. 1488/94. In 2005 the environmental risk assessment for musk xylene concluded that there was a need for further information and/or testing because the substance is considered to be a PBT candidate chemical and a further PBT ¿ testing strategy was proposed. Conclusion regarding persistency: the extractable part of musk xylene in sediment is subject to anaerobic degradation with half-lives of equal to or below 60 days. Musk xylene is therefore considered to be not persistent in sediment. In this assessment the observed irreversible binding to sediment is considered as dissipation. Given the fact that the metabolites in the ocean die-away test stayed in the water phase while the parent compound musk xylene volatilized and the fact that the ratio metabolites : parent compound was still close to one after 159 days, it is concluded that the half-life for biodegradation in seawater is more than 150 days, which significantly exceeds the criterion of 60 days. Musk xylene is therefore considered to be very persistent in water. Conclusion regarding bioaccumulation: The experimental bioaccumulation studies for musk xylene in fish showed a wide range of BCFs, among which values above the vB criterion of 5,000 l/kg. Based on the evaluation of the critical study and its results it can be concluded that musk xylene is very bioaccumulative. Conclusion regarding toxicity: there is no substantiated evidence that musk xylene can cause endocrine disrupting effects. However, musk xylene is classified as Carcinogenic Category 3), although it is realised that it is a borderline case. The overall conclusion for musk xylene is that regarding toxicity it is considered to be a borderline case. However, in view of the vPvB properties of musk xylene, no additional testing is required. It is concluded in the Addendum that musk xylene is a very persistent and very bioaccumulative substance and is considered to be borderline T. This should be further considered under the REACH Regulation.JRC.DG.I.2-Chemical assessment and testin