Drinking water
The Drinking Water Inspectorate (DWI) has published
its annual report for the year 1996 showing that there have again been
improvements in drinking water quality with 99.7% of tests showing compliance
with the standards(1). The number of tests failing to meet the standards in 1996
was one fifth that of 1992. Clearly water companies have been addressing water
quality, rather than fixing leaked pipes, which has been the focus of media and
political attention in recent months.
During 1996, 23 pesticides were reported above the EU
standards of 0.1 ug/l. With one exception (the organochlorine heptachlor) the
highest concentrations were within the ranges considered acceptable by
international standards. Although heptachlor as a pesticide has been banned in
the UK since 1981, it was reported at a concentration of 0.13 mg/l, which is
greater than the World Health Organisation Guideline Value of 0.03 mg/l.
The DWI also produced a report on nitrates, pesticides and
lead for 1995-96(2). It found that despite the improving trend of compliance
with drinking water standards, an increasing number of active ingredients are
being detected above the EU standard. Ten new pesticides were detected above the
limit including chloropropham, prophachlor, heptachlor, and DDT and its
metabolites.
The DWI says the number of positive results is decreasing and
therefore less intensive analysis is needed because of improving standards.
However, predicting which residues are going to occur is subject to doubt as
many residues are found from persistent active ingredients that are no longer in
use in the UK such as heptachlor and DDT.
Groundwater and pollution incident reports
The Environment Agency has produced an overview of the
extent and character of groundwater pollution from point sources in England and
Wales(3). There are a number of non-pesticide sources of contamination, but the
three most frequently identified pesticide contaminants were atrazine, simazine
and dieldrin. It is worth noting the time-scale at which groundwater
contamination occurs as dieldrin was banned in 1989 and the other two were
severely restricted in 1992.
The number of groundwater pollution incidents relating to
pesticide contamination is thankfully low in comparison to general organic
compounds (hydrocarbons, solvents and landfill leachates). However, the severity
of pesticide contamination occurrences is greater than for most other
categories.
Another Environment Agency report on water pollution
incidents(4), identified about 60 substantial chemical pollution incidents
involving pesticides and sheep dips (the exact figures are not clear from the
report). In particular, the change of sheep dips from organophosphates to
synthetic pyrethroids is of concern to the Agency (see box).
National pesticide database
The Environment Agency has produced a CD-ROM that
contains data from all the monitoring of controlled waters and discharges for
pesticide residues in England and Wales(5). Data is available from sampling of
fresh surface waters, groundwaters, marine waters and also trade effluent by the
Agency in the years 1992-1995.
Water quality standards
In 1995, the National Rivers Authority (now part of
the Environment Agency) monitored 158 pesticides and recorded almost 200,000
results in surface freshwaters from 1,705 sites(6). At 135 of these sites (7.9%)
the Environmental Quality Standard (EQS) for at least one pesticide was
exceeded.
The most frequent exceedences in 1995 were for the sheep dips
diazinon, cyper-methrin and propetamphos, and there was a significant increase
in the number of samples failing for cypermethrin compared with 1994 (see also
box). These are mainly associated with textile industries involved in processing
wool, but were also seen in upland areas, where they probably occur as a result
of incorrect use and disposal of sheep dips.
Agency analysis shows EQSs were exceeded for chemicals used
for mothproofing -such as permethrin, cyfluthrin and PCSD/eulan-also
associated with the textile industry. The Agency says that actions have been
taken to prevent EQS exceedences in the future, but some issues are complex and
long term solutions are needed.
The cereal herbicide isoproturon has continued to cause
concern in surface freshwater. The percentage of failures (over the EU 0.1 mg/l
level) increased steadily since 1992 from 10% to 17% in 1995. A stewardship
campaign, including reducing the application rate by 40%, has been initiated by
industry, but the Agency says it is too early to tell whether this has had any
real success in reducing concentrations during 1996. If there is no improvement,
the Agency will press the Pesticides Safety Directorate to review the approval
of isoproturon.
A clear downward trend has been seen in detections for the
herbicides atrazine and simazine (formerly heavily used in the non-agricultural
sector ). However, the rate of decline has slowed between 1994 and 1995, and the
continuing exceedences indicate the remaining agricultural use of both of these
herbicides is likely to result in future breaches of the EU standard. The Agency
is particularly worried about atrazine use on maize because the area devoted to
this crop is increasing rapidly.
The Agency concludes by saying that a national strategy aimed
at minimising pollution of the water environment by pesticides should be
produced and implemented. (DB)
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Environmental worry with new
synthetic pyrethroid sheep dips
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