Chlorpyrifos pollution kills fish
In August 2001, UK Environment Agency officers traced the source of a pesticide which has killed hundreds of fish on the River Ouse in Southern England to the insecticide chlorpyrifos.
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Bacteria infected bream from the River Ouse.
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Fish have been found in a shocking state after chlorpyrifos, a
broad range organophosphate (OP) used to control caterpillars and other insects,
has been found in samples taken from the River Ouse. The amount of chemical
released is calculated to be small, only about half a pint (0.25 litre).
Analysis of river water shows concentration levels to be less than 0.001mg (part
per million) per litre , however, this is sufficient to kill river bed
invertebrates and cause harm to fish.
The Environment Agency (EA) believes that the pesticide
weakened the fish sufficiently that they succumbed to a bacterial infection
which attacked their flesh. Fish were found in a very poor condition, some still
alive with their spines protruding.
EA Sussex Area Fisheries Manager, Stuart Taylor said, 'We
believe that the presence of the pesticide in the water was the initial cause of
these fish deaths, although we will also be continuing to research the source of
the bacterial infection.'
The pesticide loses its potency over between 10 and 20 days
and the river will recover, but it will take time. EA investigations have found
that all aquatic insects along a 20 kilometre stretch from the Sheffield Bridge
area downstream, have been wiped out. This will leave a significant gap in the
food chain. Although molluscs have also been hit, EA officials have seen some
that have survived and there are also fish that remain healthy in the Ouse.
Fortunately the other tributaries are not affected, which
will enable the repopulation of the main river. The EA will continue to monitor
the progress of the river very carefully over the next few months.
'We have traced the point at which the pesticide entered
one of the feeder streams of the Ouse and legal action is being considered by
the Agency's Legal Team. The amount of pesticide involved in this incident is
small but it has caused tremendous environmental damage. Individuals must take
all the proper precautions when using any agricultural chemical and make sure
that containers are washed out and disposed of properly.' said Stuart Taylor.
The low concentration of the pesticide in the water means
that it does not pose a serious threat to river users, however the EA is still
urging the public to exercise caution and recommend that they do not touch the
dead fish or eat any which have been affected.
'We have been very grateful for the help from the Public by
way of our hotline, once again their vigilance has helped to save the
environment from further damage,' he said.
There have been many other concerns about the OP chlorpyrifos
in recent years. In the year 2000 it was severely restricted in the US after the
most extensive review of a product ever carried out by the Environmental
Protection Agency because of possible effects on the nervous system,
particularly after exposure to children.
A recent study of pesticide residues in food shows that
chlorpyrifos is one of the most frequently detected residues in food in 12
European countries, including the UK.
The Advisory Committee on Pesticides, which advises UK
ministers on safety issues is concerned about the chemical and has examined
chlorpyrifos on seven out of the last eight published meetings.
EA Traces Source of Ouse Fish Deaths, Report No 181, Environment Agency for England and Wales, 21 August 2001, http://www.environment-agency.gov.uk
[This article first appeared in
Pesticides News No. 53, September 2001, page 11]