Occupational exposure to OPs, research

Research relating to occupational exposure to OP compounds

Toxic Chemicals in Agriculture, MAFF, 1951

The press refer to the IOM Edinburgh report as "The first evidence of chronic damage related to OP sheep dip exposure". In 1951 MAFF commissioned a report, Toxic chemicals in agriculture, from a high-level scientific committee chaired by Lord Zuckerman. This concerned two chemicals, the weedkiller dinitro (DNC), and OP pesticides. It stated that "OPs can be absorbed through the skin, by inhalation and by ingestion", and that "chronic toxicity is the main problem". The recommendations for the medical profession are particularly important. None of them have been implemented to this day.

This report states that:

Medical supervision should include routine medical examination at weekly intervals, with suspension of workers who show any trace of early toxic symptom.
All workers and other persons handling the materials or otherwise exposed to risk should receive detailed instructions on dangers and precautions.
A notification should be sent to the local doctor before spraying operations are undertaken in his area.
Chemical manufacturers should not market any insecticide until they have thoroughly studied the acute and chronic toxicity of the compound, and issued extensive information about its toxic nature.

If the recommendations in a) had been carried out there would be a very important body of medical evidence of human reactions to OP exposure which would have averted the disastrous situation we are now in.

The report concludes:

Our task is therefore to recommend measures for the protection of the workers who are handling these chemical compounds in agriculture, on the assumption that they will be used on an increasing scale.

Zuckerman's 1951 committee had not envisaged the widespread uses of OPs that we see today, and certainly had never considered the obligatory use of OP sheep dips. These recommendations have never been implemented by the chemical manufacturers or successive governments, and OPIN has repeatedly asked why, and why this report has not been made available to doctors and members of the farming community, as well as the general public.

Health and Safety Executive MS17

In 1981 a group of HSE doctors published Biological monitoring of workers exposed to organophosphates, Medical Series 17. This lists the symptoms of exposure to organophosphates, and states that "repeated low level exposure results in cumulative toxicity". It says that solvents present in OP formulations can penetrate protective clothing, and, most importantly, gives a list of symptoms which can be experienced by people suffering from occupational exposure. The existence of this document has never been revealed to the medical profession, farmers or even the majority of HSE officials. This document was published again in 1987, the circulation appears to have been restricted to some academic institutions, and the factories which manufacture OPs.

Report by the Institute of Occupational Medicine, Edinburgh, on the effectiveness of protective clothing

This report, Occupational hygiene assessment of exposure to insecticides and the effectiveness of protective clothing during sheep dipping operations (TM94/04), was published in 1994. It was commissioned and funded by the National Office of Animal Health, the corporate voice of British agrochemical companies. It was a study of the effectiveness of personal protective equipment (PPE) in relation to OP sheep dipping. It was carried out by a team at IOM Edinburgh, and it compares the uptake of OPs, as measured in urinary metabolites, among dippers wearing full recommended PPE with that of a study done the year before, where no particular PPE was worn. It was noted that the uptake was almost exactly the same.

On p 31 of this report there are pertinent comments on the reliance upon PPE in occupational hygiene strategies:

Total reliance on protective clothing is normally regarded as either a first (eg in an emergency situation) or last resort in occupational hygiene control strategies… The use of such a technique would not be countenanced in industry as a long term solution

This gives the lie to the oft-repeated excuse of government advisers, that the chronic sickness of OP-exposed workers is mainly due to the foolish lack of care by farmers in not wearing the recommended protective clothing.

It is also interesting to analyse the changes in advice given by HSE/MAFF on recommended protective equipment in their sheep dipping leaflets over the last few years. These include a change from the original advice advocating the use of rubber protective clothing, to advising the use of thick nitrile equipment; and denials of the need for respiratory protection (RPE) suddenly altered in the 1995 leaflet to advice that - under certain circumstances - the wearing of RPE might be considered. These circumstances include pouring concentrate or cleaning spillage in a confined space, dipping inside a building or other enclosed area and working with freshly dipped sheep in still air conditions. The RPE should be a "full mask respirator… with a filter capable of removing particles and gas/vapour".

Report by the Institute of Occupational Health, Birmingham, July 1999

This report, An investigation into the possible chronic neuropsychological and neurological effects of occupational exposure to OPs in sheep farmers, was commissioned, approved and funded by HSE, and carried out by the Institute of Occupational Health, Birmingham University.

The team looked at a group of sheep farmers and dippers with no previous history of OP ill health. They found that there were distinct differences between the dippers and the control group:

The performance of the sheep dippers was significantly poorer than that of the control group (quarry workers), on three of the neuropsychological tests.

The tests measured reaction time, information processing and linguistic and syntactic reasoning.

Although the IOH team described these as "subtle differences" they confirmed that:

These results indicate the presence of chronic effects in certain areas of cognitive functioning.

These conclusions caused an uproar in government circles, and the then MAFF minister, Douglas Hogg, rubbished its findings in the House of Commons. This study is highly regarded in international scientific circles.

Report by the Royal College of Physicians and the Royal College of Psychiatrists (1998)

This report, OP sheep dip - clinical aspects of long term low dose exposure, was set up at the request of the Chief Medical Officer of Health, who had been approached by Baroness Cumberlege, the then Minister of Health. Among the many recommendations for improving the clinical handling of possible OP poisoning cases it suggested that more research must be carried out into possible chronic effects of OP exposure. It stated that:

Existing clinical services for patients with symptoms associated with OP sheep dip exposure are unsatisfactory… Consideration should be given to setting up groups of specialists… to complement National Poisons Information Services treatment centres.

Professor John Newsom-Davis, Chairman of the joint working party said: "I hope that this report will result in greatly improved medical care for those unfortunate sufferers from OP sheep-dip exposure and that it will prompt further research".

This report emphasises the shortage of well-constructed research projects in relation to chronic effects of "long-term low-dose" exposure. By this the report means the normal exposure of dippers, working in the real world, where there can be no scientifically accurate measurement of dosage (by which is meant exposure levels), and where cumulative absorption is occurring. It is not possible to conduct tests on human beings in which they are deliberately exposed to differing levels of OPs, as such research, except that previously carried out at the then Chemical and Biological Defence Establishment at Porton Down, is illegal.

Report by the Institute of Occupational Medicine, Edinburgh, 1999

It is therefore extraordinary that the results of the 1999 IOM Edinburgh study, which did look at "low-dose" exposure and found a correlation between that and evidence of peripheral chronic neuropathy and neuropsychological damage, should not have resulted in decisive governmental action; instead, the then Minister of State in MAFF, Jeff Rooker, asked the chemical manufacturers to consider redesigning dip cans. There were no recommendations for setting up groups of OP specialists, or funding research projects to identify the underlying causes of chronic OP poisoning, no admission that governmental advisers' denial of a causal link between OP exposure and chronic ill health had been wrong, no discussion of how hundreds of sheep farmers and workers had been wrongly advised as to the safety of OP use or the effectiveness of protective clothing… nothing but discussions with the dip manufacturers and one ineffectual letter from the Chief Medical Officer of Health, which suggested that GPs should be responsible for treatment and diagnosis of possible OP patients, and that we must all wait still longer to find out what the DOH COT/OP Working Group would say in their report, to be published later in 1999.