Sheep dip chemicals and water pollution.

The Tweed River Purification Board's objective of reducing the numbers and significance of water pollution incidents by a proactive approach based on persuasion and education is described. This has consisted of prioritising potential pollutant sources which have then been investigated in detail followed by discussion and agreement with dischargers as to remedial measures. The paper describes in detail the Board's investigation of pollution from the organophosphate (OP) sheep dips, Diazinon and Propetamphos, and their effects on surface waters throughout its area. Examination of historical incidents and a preliminary survey of sheep farms in the Ettrick Water catchment in 1989 confirmed the potential for serious pollution. Comparison of OP concentrations in the Ettrick with strategic sites throughout the catchment confirmed the widespread nature of the problem and led to visits to every sheep farmer in the Board's area in 1990 and 1991, when 795 dippers were investigated. The study involved risk assessments of the location of dippers and the spent dip disposal practice which confirmed that poor siting, inadequate disposal and particularly poor management of the dipping operation were responsible for the pollution problems observed. Practical advice on the management of dipping and disposal of spent dip was given individually to farmers. The success of the project in reducing pollution is reflected in a significant and sustained reduction in OP concentrations in environmental samples. The future of ectoparasitic treatments for sheep, the potential for antidotes to spent sheep dip and legal obligations relating to its safe disposal is also considered.