The report is the result of two years' work by the Water Research Centre (WRc), funded by the NRA and the Scottish and Northern Ireland Forum for Environmental Research. Some of the results were made public last year (ENDS Report 218, pp 8-9 ), but full publication was delayed by the need to agree future policy with the Ministry of Agriculture, Fisheries and Food (MAFF) and other departments.
WRc investigated pesticide levels in soils and surface and groundwaters in and around sheep dippers in four parts of the UK. Analyses focussed on organophosphates, the most common active ingredients of dips, although some organochlorines were also identified. Tests showed high levels of pesticides in the environment near all of the sites. On the Chalk and Greensand aquifers of the Rother catchment in West Sussex, the organophosphate diazinon was found at up to 930ng/l, and present at depths of up to 19 metres. The report concluded that considerable vertical and lateral migration of the chemical had occurred and that the aquifer may become contaminated.
Surface water pollution was found in upland areas with shallow soils and impermeable rocks. At one site in the Borders region of Scotland, high levels of organophosphates were detected in a stream near a dipper. Chlorfenvinphos and propetamphos were found at up to 4,660ng/l and 1,080ng/l, respectively. These concentrations are much higher than the environmental quality standards (EQSs) proposed by the study for the protection of aquatic life (see table ).
Very high levels of organophosphates were also found in soils. At one site in Devon, chlorfenvinphos was measured at 68,000ng/l in the pore waters of a sandy riverside soil. Such contamination could threaten waters, particularly if the soil is disturbed. The study cites an incident reported by South West Water Authority in 1984 in which a river was contaminated after soil was dug up to lay drainage pipes.
One surprising finding was that organochlorines are still much in evidence near dippers - even though their use was banned or apparently discontinued in the 1980s. Dieldrin was found at 30,000ng/l and pp-DDT at 97,000ng/l in soil waters at the Borders site. At a site in Devon where a lindane-based dip had recently been used, the compound was measured at 150ng/l in soil water and was also detectable in the nearby river Taw.
Despite the environmental and health hazards of dipping, the report notes that there is currently no alternative for treating sheep scab. Dipping is therefore likely to continue - but the report recommends a ban on disposal to soakaways.
MAFF has found that 60% of spent dips are currently tipped into soakaways. Alternatives such as incineration or disposal to landfill are likely to be too costly for most sheep farmers. Incineration of a typical 2,000-litre batch of spent dip would cost about £500 and landfilling £200, excluding transport costs. Collection of dip wastes for treatment at local centres could be viable, but would require a ban on soakaways to encourage investment by waste companies.
The disposal method recommended by a MAFF code is dilution or mixing with slurry and spreading on land, preferably level and away from watercourses and boreholes. The study found that this method is likely to be less of a pollution risk than soakaways, but many farmers are unlikely to have sufficient suitable land.
MAFF's code says that soakaways are "not suitable in most places" because of the threat to groundwater. MAFF has now promised to revise the code to prohibit soakaways, in line with the Scottish Office's version, but has stopped short of a legal ban. It says that "adequate legislation and statutory codes of practice are already in place to protect the water environment".
In contrast, the report argues for regulation of sheep dip disposal to be handed to the NRA to enable the use of soakaways to be prohibited.
Two cases of sheep dip pollution under consideration by the European Commission may yet force MAFF to change course (ENDS Report 223, pp 32-33 ). The cases result from complaints that EC Directives on groundwater and drinking water have been breached by sheep dip pesticides. The Government responded to the Commission's investigation last year, but has yet to hear whether it will be taken further.