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Organophosphates (OPs) Related Research

The Government takes very seriously the fact that there are sheep farmers who believe their health has been seriously compromised as a result of dipping sheep. Following reports of possible long term neurological effects, primarily in farmers who had used organophosphate-containing sheep dip products, the Government asked the Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT) to consider whether prolonged or repeated low level exposure to organophosphates, or acute exposures to organophosphates at levels insufficient to cause overt toxicity, can cause long-term adverse health effects. In 1999 the COT published a report entitled Organophosphates.

To address gaps in the knowlegde the COT made recommendations for further research in five different areas. After consideration, Government was of the opinion that research projects to address two of the questions had already been commissioned prior to publication of the COT report. The remaining three recommendations were advertised in the Ministry of Agriculture, Fisheries and Food (MAFF) Research Requirements 2000-2001. As a result a total of six research projects were commissioned which addressed the COT recommendations, with a seventh on the effects of children and in utero exposure.

Subsequently, 10 other research projects have been commissioned by Government. In total all 17 projects commissioned since 2001:

Recommendation 1 - What are the most common patterns of exposure, clinical presentation and subsequent clinical course among people in the UK with chronic illnesses that they attribute to OPs?

Project Code Project Title
VM0299 Review of OPIN register of suspected OP related health complaints (SHAPE: Survey of Health and Pesticide Exposure - The Telephone Survey)

Recommendation 2 - How common is dipper's flu and what causes it?

Project Code Project Title
R51.242 Prospective Cohort Study of Sheep Dip Exposure and "Dipper's Flu"

Recommendation R3 - Does low-level exposure to OPs cause disabling neurological or psychiatric disease in a small sub-group of exposed persons?

Project Code Project Title
VM02115 Disabling neuropsychiatric disease in farmers exposed to organophosphates.
VM02126/VM02302 A case-controlled study of neurophychological and psychiatric functioning in sheep farmers exposed to organophosphate pesticides.

Recommendation 4 - Do people with chronic disabling illness that is suspected of being related to OPs differ metabolically from the general population?

Project Code Project Title
RR408 Genetic variation in susceptibility to chronic effects of organophosphate exposure.

Recommendation 5 - Other than acetycholinesterase inhibition, what mechanisms play an important role in the causation of adverse health effects by OPs?

Project Code Project Title
VM02116 Investigation of possible auto-immune responses induced by organophosphate exposure
VM02117 Characterisation of non-acetylcholinesterase actions of organophosphates by identification of novel protein targets

Recommendation 6 - In addition to COT's recommendations the Government also asked "what are the effects of low level exposure to OPs on children exposed directly or in the womb"

Project Code Project Title
W11 A Review of the effects of low-level exposure to organophosphate pesticides on fetal and childhood health.

Projects Commissioned In Addition to the COT recommendations

Project Code Project Title
VM0279 Dose effect profiles for OP sheep dip on brain electrical activity and cognitive performance in non-human primates.
VM02106 Development of database on research on organophosphate compounds related to public health (Survey of research projects on organophosphates (SRPOP))
VM02112 An analytical study of human OP sheep dip reports received by the VMD 1985-2000
VM02300 Effects of sheep dip pesticides on differentiating nerve cells: Identification of novel markers of toxicity
VM02301 Prediction of susceptibility to long-term genotoxic effects of organophosphate pesticide exposure.
ZEC014 Genetic and other sources of variation in the activity of serum paraoxonase/diazoxonase in humans: consequences for risk from exposure to diazinon
PS2602 Investigation of gastrointestinal effects of organophosphate/carbamate pesticide residues on young children
PR1146 A pilot/feasibility study monitoring possible side effects of organophosphate/carbamate pesticides residues on young children and infants
PS2601 Pesticides and Parkinson's Disease: A Review
PS2608 Mechanism of the association between pesticides and Parkinson's
PS2610 The Tempest Study - Epidemiology of the association between pesticides and Parkinson's disease.
PS2612 Monitoring UK pesticide exposure using National Poisons: Information Services Systems

Projects to investigate the alternatives to conventional sheep dips for the control of scab

Project Code Project Title
OD0535 Novel biologically based control methods of the sheep scab mite preliminary investigations
OD0536 Biochemical and physiological studies to identify potential targets for the control of Psoroptes ovis
OD0537 Biochemical and immunological studies in sheep infected with the mite, Psoroptes ovis
OD0538 Studies on the biological control of sheep scab mite, Psoroptes ovis, using entomopathogenic fungi.
OD0539 Potential targets for biologically based novel methods of control of the sheep scab mite by study of its basic biology and endocrinology.
OD0544 Immunological approaches to the control of sheep scab mite.
OD0545 Studies on the biological control of the sheep scab mite Psoroptes ovis.
OD0546 Feasibility of using biological studies to develop novel control of the sheep scab mite.
OD0552 Identification of novel control methods through better understanding of the biology and physiology of the sheep scab mite.
OD0553 Investigation of the potential for the control of sheep scab using immunological approaches and the development of diagnostic tools.

Much of this research has now been completed and the COT has been asked to advise on the significance of these research findings. The 1st review was carried out at the COT meeting held on 4 September 2007. As some of the research projects were still in progress, COT advised that it would need to revisit all of the work once all of the final reports were available. Furthermore, as other work has been published in the scientific literature, which includes uses of OP insecticides other than in sheep dips, COT stated that its advice could only be finalised in the context of consideration of all the available relevant research.

Apart from these broad recommendations, COT gave the following advice on some of the completed work at the 2007 meeting;

  • Research to address "How common is dipper's flu and what causes it?" has not provided evidence for a flu-like condition related to sheep dipping.
  • Two other projects indicated that those who metabolise OPs faster than the norm were more likely to report ill-health. This was the reverse of the hypothesis tested.

A complete account of the meeting is given in the minutes available on the COT website.

At the September and December 2009 meetings the COT considered projects which were not completed at the time of the 2007 review.

At the request of the COT, a full scientific literature review is now underway to place the government-funded research into the full scientific context. It is anticipated that the review will be completed at the end of 2012, at which point the COT will be able to advise the Government on the meaning of the research.

When the COT's final advice is received the Official Group on OPs (OGOP) will be consulted on the way forward with a view to taking the outcome to the Defra Minister.

Last Updated: 5 December 2011

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