Sheep Dip - The Dangers Unfold

As long ago as October 1996, the Wye Foundation Habitat Officer visited the Sgithwen brook near Erwood and found large numbers of dead crayfish. Fearing that they were victims of the 'plague' that had destroyed so many in chalk streams, he checked above the first waterfall and found the same: all dead.

The Environment Agency was contacted and their water samples revealed the presence of Synthetic Pyrethroid Sheep dip. A prosecution resulted and the Agency conducted a survey of 'at risk' streams in mid and north Wales in 1997 and again in 1998. Much to everyone's surprise and horror, It was Organophosphate dips that dominated the survey and greater than 95% of these streams were affected....

WHY DIP?

Sheep carry many ectoparasites, including sheep Scab and until recently, dipping in chemicals was the best way to treat them. The two main Sheep Dip chemicals used are Organophosphates and Synthetic Pyrethroids. In Wales sheep are often turned out on commons and dipping is the main line of defence against cross infection.

Type of Chemical

Time Scale of Usage

Effectiveness on Sheep Scab

Toxicity for Humans

Toxicity for Aquatic Life

Can it be easily neutralised?

Names of those commonly used

Organo-
phosphates

Used solely until the early 1990

High

High

High

Not Easily

DIAZINON
PROPETAMPHOS

Synthetic
pyrethroids

Introduced in the early 1990

Low

Low

High (100 x more toxic)

Yes

CYPERMETHRIN
FLUMETHRIN

There are now alternative methods that are slowly being introduced which should help to reduce the level of pollution in the future. These include injections, jetters or showers and pour-ons.

IS IT REALLY A PROBLEM?

YES!

The results of the Environmental Agency Survey in 1998 clearly shows that the sheep dip pollution is widespread and whilst the synthetic Pyrethroids are known to be more toxic to Aquatic Invertebrates, Organophosphates are the major hazard, maybe more than originally realized.
In the 1998 survey 16% of farms visited were found to be high/very high risk of polluting a stream/river. This was an improvement on the 1997 survey, where 26% of the farms surveyed were found to be of high/very high risk.
However from the results of the surveys it is also seen that far more of the streams are effected than previously thought and it is actually possible that even these results do not give the whole picture.

YEAR

Percentage of stream treated in High/Very High risk areas

Probable length of stream affected

1997

4.9

700 km

1998

10

1200 km

Of even greater concern, however, are the findings of recent research, which highlights the dangers to salmonids of the effects of certain chemicals in very low doses. It appears the hatching stages of trout and salmon and the migration phases of salmon are significantly compromised, even with doses below the current acceptable levels and there are concerns too regarding the retention within stream systems.

HOW IS THE POLLUTION OCCURING?

  1. The actual structures used for dipping are a major concern.
    The main problems include:-

  2. Methods of disposal are a concern - spraying over farm land - especially with Organophosphates. These can remain in the soil for a very long time, whilst it is technically possible to neutralise synthetic Pyrethroids. The 1998 survey did show that farmers where becoming far more aware of the effects upon the invironment and the need for safer disposal of the dips.

  3. Facts about sheep in Wales

WHAT CAN BE DONE?

"A national strategy for sheep dip must achieve a balance between the requirements of the agricultural industry and the need to protect the environment" (Environment Agency strategic review of Sheep dipping; technical report P170).

  1. Fishermen can act as first hand detectives by checking for invertebrate life when visiting the rivers. (See Pollution incidents)

  2. In depth water quality monitoring, especially during peak dipping times (June - November).

  3. Promoting a code of good practice for disease control in sheep, to include appropriate location and construction of dipping facilities.

  4. Developing and promoting positive flock management so reducing the need to dip and also the use of alternative methods.

  5. Extensify sheep stocks.

  6. Ban of Synthetic Pyrthroids

The Foundation, through its projects and with other groups, is promoting river care. We see a need for change in the perception by farmers that water courses are a conduit for litter and waste chemicals.