Pesticides in water on the increase

Increasing numbers of pesticides exceeded water quality standards in 1995, according to a report from the Environment Agency.1 The Agency ascribes the upturn to intensified monitoring and better analytical methods - and holds out little hope of significant reductions in pesticide pollution in the near future.

The report is the third to review pesticide monitoring carried out by the former National Rivers Authority (NRA). The Agency has assessed the 1995 results against environmental quality standards (EQSs) set by the Department of the Environment (DoE), used by the NRA or proposed by WRc. It also notes where pesticide levels exceeded the 0.1µg/l limit set by the 1980 EC Directive on drinking water quality.

The NRA monitored 160 pesticides in freshwaters, coastal waters and groundwaters in 1995, taking almost 250,000 samples from over 2,500 sites. In 1992 and 1993, it monitored only 120 substances.

A key finding was that exceedances of EQSs and drinking water standards appear to be increasing. 7.3% of freshwater sites failed EQSs for at least one pesticide in 1995 compared with 3.8% in 1993 (see table ), while 75 pesticides exceeded the drinking water limit in 1995 compared with 52 in 1992.

Alan Barnden of the Agency's National Centre for Toxic and Persistent Substances (TAPS) says it is "difficult to say whether the overall situation had got better or worse" as the same sites were not examined each year. The Agency is moving towards a targeted survey, beginning in 1998, which will allow firmer conclusions about trends in pesticide levels. "At the moment we are only monitoring a third of pesticides and we only have EQSs for 10%," he said.

The report notes a significant increase in breaches of the EQS for cypermethrin arising from its use in sheep dips. These dips have become increasingly popular, but have a high toxicity to aquatic invertebrates (ENDS Report 263, pp 4-5 ).

Along with cypermethrin, the sheep dip pesticides diazinon and propetamphos are the main cause of EQS exceedances. They enter watercourses through improper disposal on farms, but mainly via wool industry discharges.

The textile industry also causes EQS breaches for the mothproofing compounds permethrin, cyfluthrin and PCSD/eulan. The report claims that some improvements have been made in these discharges since 1993 but these are not apparent in the monitoring data. A working group was set up last year to investigate ways of removing pesticides from textile industry discharges, but the Agency holds out little prospect of quick solutions.

Most exceedances of the 0.1µg/l drinking water standard in surface waters were caused by the herbicides isoproturon, diuron and mecoprop. Failures due to isoproturon rose steadily from 10% in 1992 to 17% in 1995. Modifications to the product's approval conditions were made during the year and manufacturers launched a stewardship campaign, but it is too early to judge whether these measures are succeeding in reducing environmental levels.

Concentrations of the herbicides atrazine and simazine in surface waters fell significantly following a ban on non-agricultural uses in 1992. The remaining breaches - about 10% of simazine samples and 4% of atrazine samples - appear to be due to agricultural use. The Agency is particularly concerned about their potential to cause groundwater pollution and has pressed the Ministry of Agriculture to consider restricting their use in sensitive areas.

The report revisits 20 recommendations made in 1995 to reduce pesticide levels in water, including the establishment of a working group to develop a national pesticides strategy, promotion of agricultural measures such as buffer strips and no-spray zones, and liaison with manufacturers to promote better formulations.

Progress has been modest. The first meeting of the pesticide strategy group was held in May. Discussions with manufacturers appear to have come to nothing so far, while action on agri-environment schemes is awaited from MAFF.

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