Genetic factors may increase risk from OPs

Dr Povey talks about three pieces of OP-related research he has worked on: one complete, one ongoing and one brand new.

The SCOPE study

In 1999 and 2000, research nurses interviewed over 400 sheep farmers throughout the UK and obtained information on their health, their working practices and their exposure to pesticides. The research nurse also took a blood sample so as to examine the genetic make up of the individual farmer. This study was undertaken by the SCOPE research team, based at the University of Manchester. Nicola Cherry and her colleagues were interested in examining whether people who differ in their ability to remove toxic organophosphates may, if exposed, be at increased risk of ill health. Previous work had shown that one specific protein, paraoxonase, is important in removing toxic organophosphate metabolites and that this protein exists in different forms which differ in their ability to remove these toxic compounds. People with different paraoxonase forms may thus be at differing risks of susceptibility to organophosphate toxicity.

This study tested this idea by comparing the different paraoxonase forms in sheep farmers with chronic ill health which they thought due to exposure to sheep dip (cases) with those found in other sheep farmers with a similar dipping history but who remained healthy (controls). Results showed that cases and controls did differ in their genetic make up and that cases were more likely to have the form of the paraoxonase protein that made them less able to break down organophosphates once they had got into the body. It was not possible to determine whether, for any one subject, their ill-health had been caused by organophosphates, but these results did support the idea that some people may be particularly at risk from working with organophosphates.

SHAW Study of Health in Agricultural Work

For more than a decade there has been increasing concern that farmers may be at greater risk of ill health due to their occupation. Most previous studies have looked at the health of working farmers, which doesn’t take into account the many retired farmers, or those who have stopped farming altogether due to ill health. This may result in biases that underestimate the extent of ill health in the farming community.

To investigate both working and retired farmers, the University of Manchester’s Centre for Occupational and Environmental Health is requesting the assistance of farmers across the UK to take part in a study looking at long-term health effects of farm work. This project called SHAW (Study of Health in Agricultural Work) has been carefully scrutinised and approved by an ethics committee. It is supported by the National Farmers’ Union and the Farmers’ Union of Wales, and is funded by the Department of Health and the Department for Environment, Food and Rural Affairs.

The researchers will document the current health status of people who were farming in the 1970s and examine whether the health of farmers varies with the type of work carried out. In order to reach as many farmers as possible the researchers will contact individuals who were farmers in the early 1970s. They have obtained the names of about 20,000 farmers from the National Farmers’ Union, Shepherd’s Guides and sheep and cattle associations. The farmers will be contacted during the winter of 2003/04 and will be asked to complete a brief questionnaire.

The questionnaire has been produced with the help of several groups of farmers, ensuring that it is tailored specifically to those within this occupation. Dr Andrew Povey, Lead Investigator for the study commented: We met with groups of farmers during the design of the questionnaire, and all were impressed with the fact that it took only 15 minutes to complete and was not too intrusive or complicated. There will be a follow-up to the questionnaire for a small proportion of those who respond, which will allow the researchers to investigate further some of the health problems reported by participants. The results will then be used to determine whether certain groups of farmers could have experienced health effects from their farming activities, which will benefit both current and former farmers by helping to establish whether or not certain diseases are a hazard of their occupation.

Participation in the study is entirely voluntary and participating farmers will be able to withdraw at any time. The research team stress that any information provided by individuals will be used in the strictest confidence and will not be passed on to any third party. The success of the study is dependent on a good response rate so the return of as many completed questionnaires as possible is very important. Further information about the study can be found on the website at www.coeh.man.ac.uk/research/shaw/

Study of sheep dip exposure and dipper's flu

This is new research into acute ill health in sheep dippers. Farmers often complain of ill health within days of dipping sheep a condition commonly referred to as dipper's flu. Little is known about dipper's flu or the extent of the problem or indeed what causes it. Much attention has focussed on the toxic effects of organophosphates present in some sheep dips but it is possible that other substances such as infectious agents may also be involved.

To determine how widespread dipper's flu is and to identify its causes, a research team consisting of scientists from the University of Manchester, the University of Wales College Of Medicine Cardiff, and Guy's & St Thomas' Hospitals, have started a new study in sheep dippers which will take place over the next two years. The team hopes to recruit 1000 dippers in Mid Wales, the North West and Southern England and to follow them through a dipping season in order to obtain information on their symptoms after dipping. The farmers would be visited by a research nurse and be asked questions about their health, their job and their lifestyle. Blood samples would be taken and analysed to identify which agents the farmers had been exposed to. Differences between those dippers who became ill and those who didn't should lead to a better understanding of the causes of dipper's flu and ways to prevent people being affected.