Doctors add their voice to farmers’ call for action over OP sheep dips

A joint seminar on organophosphate (OP) sheep dips and human health, organised by the National Farmers Union and the British Medical Association, has heard calls to ban OP sheep dips. Becky Allen and Peter Beaumont report on this and the conclusions and disagreements over the interpretation of scientific research.

Research controversy: what is good science?
The debate about OPs, sheep dips and human health has been further complicated by disagreements between government agencies over research design and results. The government now proposes a system of open tendering to procure different research.
    At a joint seminar of the National Farmers Union (NFU) and British Medical Association (BMA), Dr Anne Spurgeon of the Institute of Occupational Health, an author of the OP study sponsored by the  Health and Safety Executive (HSE),(1) presented findings of research which demonstrated long-term effects on the nervous system from the use of OP sheep dips (see PN28 p3). However, the Veterinary Products Committee (VPC), which advises Ministers on veterinary medicines (including sheep dips), has subsequently disagreed with the conclusions reached in the study. A VPC press release stated the agency's opinion that firstly, differences between the control and sheep farmers could have been due to a wide range of factors; and secondly, it did not accept that the chronic health effects found in sheep farmers are due to long-term low-level exposure to OP sheep dips. It considers there were 'uncertainties' in the report.
    There is no obligation on the VPC, which is an independent committee, to accept the research findings of others. However, the research was publicly funded, and the study design and protocols were, we presume, agreed beforehand. The research has been peer reviewed and published in The Lancet. We have written to the VPC asking them to set out in more detail their disagreements with the conclusions.
    In the meantime, tender proposals for “carefully designed and targeted epidemiological studies of the effects of OP sheep dips” are being evaluated. But is that not what HSE is already supposed to have done?
    In what was to be his last day as Minister of Agriculture before being reshuffled to the Treasury, William Waldegrave told the Agriculture Select Committee that the government would act to ban OP sheep dips if further evidence was forthcoming that OP products could not be used safely. There was no doubt, he said, that OP dips are dangerous products. “The question is, can they be used safely? We are doing a range of further work,” he explained, “and if it shifts the balance of probabilities, we will ban the products.”

Farmers frustrated
Mr Waldegrave’s promise of further research however is unlikely to have impressed sheep farmers who have been poisoned by OP dips. At a seminar on the subject organised by the NFU and the BMA on 2 June(2)  many farmers and doctors called for an immediate moratorium on OP dips, and compensation for those whose health had been ruined. The seminar, attended by over 100 doctors and farmers, at times reached boiling point as frustrated sheep farmers poisoned by dips struggled to maintain what little patience they have left with a medical and legal system they feel has failed to safeguard their health or listen to their claims.
    Many sheep farmers have been critical of the NFU in the past  for failing to support members who have been poisoned by OPs, but Tony Pexton, Deputy President of the NFU, told the seminar that the union “now finds the mounting evidence suggesting a direct link between OP dips and human health effects extremely worrying.”
    The adverse effects of acute exposure to OPs are well-known: high level exposure results in acute effects on the nervous system, characterised by anxiety, irritability, restlessness and headaches, due to inhibition of the neurotransmitter cholinesterase. In extreme cases OP poisoning can lead to heart or respiratory failure.

The longer term effects
Current research is now focusing on the cumulative effects of long term low dose exposure. Concerns have been expressed that such chronic exposure may result in loss of memory, lack of concentration and other mental health problems.
    Dr Timothy Marrs, of the Department of Health made three points. Firstly, he challenged the conventional wisdom that low doses of OPs do not produce irreversible effects on the central nervous system. Secondly, he drew attention to the relatively new 'intermediate' syndrome which was described in the 1980s. This produced longer term effects on the muscles—a proximal limb paralysis which can occur between one to four days after an acute poisoning, and which will not respond to drug antidotes, and can paralyse muscles to prevent breathing. As he commented “OPs have been around since the 1930s and 50 years seems rather a long time to find a new syndrome.” Thirdly, he noted the delayed effects on the peripheral nervous system—such peripheral neuropathy—can begin some seven to 14 days after exposure, and can lead to a partial or complete paralysis,  which causes pathological changes in some of the larger nerves.
    Dr Goran Jamal, a consultant clinical neurophysiologist echoed these comments. He reported on his research findings that OP induced delayed neuropathy may be more frequent among the users of OP compounds than had been thought. Chronic illness could result as a consequence of repeated exposure to very small doses that themselves produced no manifest clinical effect.
    Robert Davis, a consultant psychiatrist from Taunton, Somerset, explained that because OPs interfered with serotonin levels in the brain, it was likely that OP exposure also had a role to play in the high levels of suicide recorded in farmers.
    OPs are also known to cause arrhythmias and myocarditis (heart defects)—the latter condition is illustrated by a case study from Dr Richard Bernhardt, a Kent GP. In 1991, one of his patients, who worked on a sheep farm, presented with ‘flu-like symptoms, vomiting, and chest pains two weeks after dipping his flock with a dip containing the OP active ingredient propetamphos. He was diagnosed as suffering from myocarditis, but recovered until the 1992 dipping season when similar events occurred; this time he needed resuscitation after he suffered a cardiac arrest. Despite remaining well during 1993, when he stayed away from OPs the worker was hospitalised again in 1994 simply after he had walked through a field of sheep that had been dipped in OPs. Many months later he is still not fully recovered and shows evidence of heart damage.
    Unlike Dr Bernardt, many GPs may be failing to diagnose correctly the non-specific symptoms that OP poisoned victims present them with, according to the BMA. “It is clear that doctors need more training and practical experience in the diagnosis and treatment of patients exposed to agrochemicals” admitted Dr Fleur Fisher, the Head of Ethics, Science, and Information at the BMA. More toxicology training in undergraduate medical courses and continuing medical education for practising doctors was necessary.

Alternatives to OP sheep dips Alternatives to OP dips are available, but are more expensive. How safe they are may be open to question (see p3). The most recent addition, Robust, which has clearance for use on both strike and scab, the two main afflictions of sheep treated with OPs, is three times the price of OP dips. The complete range of products available, including OPs and non-OPs, together with indications for use, has just been published by VMD, and alternative treatments to OP dips for sheep scab or blowfly strike are summarised below.
Non-OP treatments
Product (active ingredient)	Fly Strike	Scab
Ciba Vetrazin Pour-on(cyromazine)	Y
Coopers Spot-On (deltamethrin)	Y
Ciba Parasol Pour-On (cypermethrin)	Y
Youngs Cypor (cypermethrin)	Y
Coopers Green Label Scab and Tick Dip (flumethrin)		Y
Bayticol Scab and Tick Dip (flumethrin)		Y
Youngs Robust/Crovect (cypermethrin)	Y	Y
Veterinary medicinal products (dips, injectables, pour-ons and sprays): available in the UK for use as ectoparasiticides in sheep, VMD, July 1995, 12 pp., free, (also see this issue of Current Research Monitor).

Does protective clothing reduce the risks?
The Pesticides Trust [now PAN UK] considered the reliance on protective clothing alone is unsatisfactory. As far as sheep dips are concerned, simply reading the label and wearing waterproofs is no guarantee of safety. Use according to label directions on its own is not safe use. The wearing of protective clothing is one of the last lines of defence against a toxic chemical, not the first. The Control of Substances Hazardous to Health Regulations (COSHH) prescribes a step-by-step process to reducing risk.
    The steps include deciding whether a chemical has to be used at all (elimination); if so, then using the least toxic option (substitution); reducing exposure by the use of technical and engineering controls; and if exposure still cannot be avoided, then protective clothing—or personal protective equipment (PPE)—should be worn.
    PPE has to be both suitable and adequate, according to EC Directives. Much has been made of the recent HSE research comment that although waterproof trousers were worn by 90% of users, and waterproof footwear by 88%, only 23% wore gloves, 7% face coverings, and 5% head coverings. Does this amount to contributory negligence by farmers? Or is it perhaps evidence instead of the impossible burden on farmers, requiring them to wear PPE that the experience of many will say is unsuitable for the majority and inadequate for the minority: unsuitable in that it is not worn because it is impractical to wear, and inadequate because it cannot protect the few who are truly vulnerable.
    Many farmers argue that dipping sheep while wearing full protective clothing is simply not feasible. This was a point echoed by Tony Pexton of the NFU “There is a strong view among sheep farmers that the safety equipment and clothing required to provide—as the HSE advise—adequate protection, would make it impossible physically for the farmer to do the job.” Several of the farmers, who had travelled to the seminar from sheep farming areas in Wales, the South West, and Northern England, claim to have suffered OP poisoning even though they adhered to HSE guidance on protective clothing. One such was Brenda Sutcliffe from Rochdale, whose entire family suffered severe OP poisoning after the 1992 dipping season. She, her husband and sons were all poisoned despite being “geared up like men from Mars”.

The role of expert committees
For many years, dipping has been mandatory, and farmers have had no choice but to use OP products. Now they are being told that their health may be damaged, but that provided they acquire a Certificate of Competence they can buy OP dips (although anyone can actually use OP dips, as opposed to purchase them). Many present were critical of the regulators for not heeding the warnings as long ago as 1950 on the use of OPs.
    There is no involvement of dip users—sheep farmers—in the risk assessment process. The VPC decides whether or not certain chemicals can cause particular effects. However, the acceptable risk of such hazard occurring is surely a process in which those who run the risk should have a say.

The next step?
The joining together of farmers and doctors could make a powerful argument for change, reducing the current use of OP dips. Both organisations have promised to work together to do this. Otherwise the exercise might be seen, in the words of one experienced counsellor, as an exercise in management only.

Key issues Based on current reporting, the Pesticides Trust estimates that at least 1,000 sheep farmers are suffering from the adverse effects from OP dips. However the figure may be higher because of significant under-reporting and under-recognition of symptoms. Workers in horticulture and grain handling are also frequently exposed to OPs in confined workplaces. Those who use pesticides should have a say in the acceptable level of risk they are prepared to run. A single system of adverse reaction reporting must be established which can investigate, counsel and advise people who may have been affected by pesticides, including OPs and OP sheep dips. A way of predicting or diagnosing users who may be sensitive to OPs is urgently needed. Risks from the use of OPs cannot be eliminated. Concerned and/or chemically-sensitive users should substitute the use of OPs with other safer dips. Control measures must be sufficient to reduce exposure. Too much reliance is placed on personal protective equipment, which is not guaranteed to be suitable and adequate for vulnerable users. Legal actions by sufferers are not the appropriate route for remedying the health impacts of environmental chemicals, including OPs. There should be commitment to establish a no-fault compensation scheme. A government commitment to a comprehensive policy of pesticide reduction is called for—including reduction of use, reduction of risks to health and the environment, and reduction of dependence on chemical pest control. In the context of control of scab and strike in sheep this means the urgent development of non-OP methods of control and the phasing out of OPs.

References
1. Stephens, R., Spurgeon A., et al., 1995, Neuropsychological effects of long-term exposure to organophosphates in sheep dip, HSE Contract Research Report 74/1995.
2. NFU/BMA, Organophosphate Sheep Dips and Human Health, Conference Report, 1995, Available from NFU, London, 40 pp.

Becky Allen writes on science issues.  Peter Beaumont is Director of the Pesticides Trust [now PAN UK].