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Environmental fate & pathways

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Monitoring data in the aquatic environment for trichloroethane is extensive. Data from either government controlled or government-sponsored agencies have been monitoring levels in the environment for over 20 years. The results included in the EUROCHLOR 1999 report and in the UK Department of the Environment 1996 report reflect the picture before the full effect of the Montreal protocol have become evident and the authors indicate that the levels recorded are probably higher than would be expected at the present time. The monitoring data is adequate to predict on an analytical basis the PEC for the marine/brackish water/freshwater environment without the need for modelling. On the basis of the information available the PEC immediately before and just after the introduction of the Montreal protocol was 21ug/L and, following the effects of restricted use imposed in the Montreal protocol, the EU required PEC of 10ug/L has probably been achieved in most situations around the North Sea coast and in North European freshwater systems.

Wakeham et al 1983 used large mesocosms to predict the rate of loss from the estuarine environment. This work confirmed that the expected half life in the marine environment is very low due to volatilisation to the atmosphere. The most interesting finding in this study is that volatilisation is not temperature driven as would be expected but is primarily dependent on the level of wave activity with the highest losses recorded during the winter period in stormy weather.

Zoeteman et al 1981 summarises the results of a survey of potential contaminants that could find their way into potable water conducted in 1976 -1978 at all 232 groundwater pumping stations in the Netherlands. The results of this survey show that the materials of most concerned were trichloroethylene (67%), trichloromethane (60%) and tetrachloromethane (43%). The authors summarise potential routes of entry into aquifers and conclude that the most probable route is from unregulated industrial waste disposal sites. Deposition from the atmosphere in rain is not thought to account for levels >0.01 - 0.1ug/L. At the time this survey was conducted the use of halogenated hydrocarbons was not regulated therefore these results should be treated as a worst-case scenario as the effects of the Montreal Protocol have severely restricted the use of these materials in industry. In addition regulatory control is now sufficient to prevent unregulated disposal and appreciable efforts are now made to recover materials such as trichloroethane to prevent environmental contamination.