chronicles of concern
By Liz Mason
FARMERS claims that organophosphorus sheep dips, approved by the governments licensing authority, have harmed their health are to be probed by an all-party committee of MPs.
The House of Commons agriculture select committee will challenge the Veterinary Medicines Directorate over its licensing of OP dips on Apr 26.
MAFF officials have consistently claimed that there is no evidence to support allegations that OP sheep dips have ruined farmers lives.
They have stated repeatedly that there is no evidence that the dips are a health risk when used in accordance with manufacturers instructions.
But those who have been diagnosed as suffering from OP dip poisoning disagree. In their campaign for recognition they have researched and drawn attention to scientific evidence on the damaging effects of OP chemicals. Evidence that they say has been suppressed and discounted.
Early research on OP toxicity was published shortly after the OP insecticide parathion was developed by a German scientist in 1944. Related compounds, or nerve gases, were manufactured during the Second World War for chemical warfare.
Research on laboratory rats found that acute parathion poisoning inhibited the production of an enzyme called cholinesterase in nerve tissue. It was also found that this could be reversed by a chemical called atropine.
Safety data sheets for sheep dips, obtained by FARMERS WEEKLY, describe the active OP ingredients as anticholinesterases. "If human poisoning occurs," says one sheet, "the symptoms will be those of anticholinesterase poisoning and the usual antidote which will deal with many of the symptoms is atropine."
Further research on the chemistry of OP poisoning was published in the 1960s. This lead to a detailed description of the effects on the sufferers muscles, heart and exocrine glands. Recognised symptoms, published in toxicology textbooks, include chest tightness, diarrhoea, nausea/vomiting, sweating, and bradycardia that can progress to heart block. Others include tension, anxiety, restlessness, insomnia, emotional instability and depression.
These are also described in the Health and Safety Executives guidance leaflet MS17, which was first published in 1981 and revised in 1987.
It also says that repeated small doses, from contaminated clothing, for example, has "cumulative effects resulting in progressive inhibition of nervous tissue cholinesterase".
Under the Health and Safety at Work Act 1974 manufacturers and suppliers of veterinary medicines have a duty to provide adequate information on the risks and appropriate precautions to take when using these products. But has this information, provided on products labels and data sheets, been adequate to protect farmers from OP poisoning?
The National Office of Animal Health claims "there have been very clear instructions on labels for over 20 years". But again campaigners and sufferers disagree.
Over the years, advice on protective clothing and warning labels on containers have been updated. Questions have also been asked in the House of Lords by the Countess of Mar on the ability of dips containing phenol to penetrate protective clothing.
The HSE guidance note MS17 and a report by the Veterinary Medicines Directorate appraisal panel also reveal that organic solvents such as phenol can have harmful effects which may be confused with the symptoms of OP poisoning.
1951. Lord Zuckermans report Toxic Chemicals in Agriculture recommends that OPs should be used only with maximum protection, including in some circumstances a respirator. It warns: "The chief danger lies in the chronic effects which result from frequent exposure to these chemicals."
1962. Protective clothing regulations introduced for OP sheep dips and other purposes.
1976. Compulsory dipping with MAFF-approved products reintroduced.
1977. HSE statistics report lists organophosphorus poisoning as a prescribed disease. Sufferers are eligible for compensatory benefit under the industrial injuries scheme. "Diseases are only prescribed if some occupational cause is well established," says the HSE.
1985. Sheep dips containing organochlorine withdrawn from the market.
October 1987. HSE publishes revised guidance note MS17. It says acute and sub-acute OP exposure can produce harmful effects in man. Detailed symptoms and treatment are described and regular monitoring, including blood tests, advised for "anything more than occasional exposure to OP compounds".
In agricultural practice the main route of absorption is via the skin, it says. "OP formulations based on organic solvents are liable to penetrate protective clothing unless washed off promptly," it warns.
When poisoning occurs "the presence and influence of the solvent should not be forgotten. Local skin effects will almost certainly be due to the solvent; in exceptional and severe cases the presence of an organic solvent may encourage considerably the development of intoxication symptoms."
December 1989. Junior farm minister David Maclean says: "Occasional hypersensitive reactions can arise even when the guidance has been observed."
March 1991. MAFF says it has received 55 reports of adverse reactions to OP sheep dips since 1985.
April 1991. National Office of Animal Health (which represents manufacturers) calls for sheep dips to be included in long-term HSE health studies. HSE says it is monitoring about 40 dip users in Devon. NFU South West survey finds one third of farmers say they are ill after using sheep dip.
September 1991. MAFF reports 121 adverse reactions to sheep dip involving 138 people.
October 1991. Health bulletin including symptoms of OP poisoning circulated to all doctors.
August 1991. HSE publishes advice leaflet AS29 called Sheep dipping: protect your health. It advises "rubber gloves, coverall and face shield" when handling the concentrate, and "rubber boots, rubber gloves and waterproof coat or bib apron when handling the diluted liquid and freshly dipped sheep".
October 1991. HSE launches new study to assess health effects of sheep dip on the human nervous system and agrees to review protective clothing advice.
January 1992. Junior farm minister David Maclean says there is "no clear evidence that sheep dips cause any unacceptable level of health risk when used in accordance with manufacturers instructions".
June 1992. Compulsory dipping scrapped. Veterinary Medicines Directorate publishes revised advisory notes on the safe handling and disposal of sheep dips. It suggests occasional blood tests may be appropriate for contract dippers regularly exposed to OPs.
October 1992. National Poisons Unit report demonstrates "a medical problem from occupational exposure to OP sheep dip".
November 1992. Sheep dips containing phenol voluntarily withdrawn from the market.
December 1992. Earl Howe tells the House of Lords that there is "no evidence that protective clothing is damaged by phenols in sheep dips when used in accordance with the manufacturers instructions".
January 1993. The Veterinary Products Committee says there is no
clear evidence that sheep dips cause an unacceptable health risk when used in accordance with manufacturers instructions. MAFF has 338 reports of adverse reactions involving 423 people.
February 1993. Farm minister John Gummer agrees to seek expert advice on "whether it would be prudent to suspend OP dip licenses".
April 1993. 350,000 Safe Use of OP Sheep Dips leaflets issued by NOAH and the VMD. For handling the concentrate it recommends: Non-lined synthetic rubber gloves (heavy duty gauntlet style PVC or nitrile at least 0.3mm thick), wellington boots, waterproof trousers or leggings, and waterproof coat or bib apron (nitrile or PVC) and a face shield.
Similar clothing, but no face shield, recommended when working with diluted dips and freshly dipped sheep.
April 1993. NFU internal briefing says there is evidence of toxicity – acute and chronic – from OP dips. It says there is a non-OP dip for those who have a traumatic response to OPs (eg, cardiac/respiratory distress).
July 1993. Chief medical officer writes to all doctors in England alerting them to OP guidance leaflets.
October 1993. VMD appraisal panel report into 161 suspected adverse reactions finds 32 likely cases. Three wore full-protective clothing, suggesting they were exposed by inhalation.
The report says in most cases it is not known whether OP, the solvent or a combination of these caused the reported ill health. This is because the symptoms of OP poisoning are similar to those caused by solvents.
The panel suggests a small section of the UK population may be susceptible to OP dips and become ill after minor exposure.
The VPC and other experts meet to discuss OP dip ban. They say new evidence confirms that acute or sub-acute reactions from OP sheep dip are "highly unlikely". They recommend certificates of competence and a new medical panel.
December 1993. Farm minister Gillian Shephard says there is
no justification for an OP dip ban and agrees to VPCs recommendations.
March 94. Ivomec injection granted a licence for sheep scab treatment.
April 1994. MAFF has 520 reports of adverse reactions involving 606 people.
May 1994. HSE launches new sheep dipping leaflet. It says "concentrated dip can get through protective gloves and clothing".
It also advises farmers to consider using a respirator when pouring concentrate in a confined space: Dipping inside a building or working with freshly dipped sheep in still air conditions. And it tells contractors to monitor their own and their employees health through blood and urine sampling.
August 1994. Government accepts medical panel advice recommending further research into the health effects of OP sheep dips
April 1995. MAFF announces that OP dip research contracts are unlikely to be awarded until late July. It claims no tenders met the required criteria.
House of Commons agriculture select committee begins its inquiry into the workings of the VMD, including its suspected adverse reactions scheme.