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Pesticide exposure and respiratory disease. Review of literature on asthma prevalence and exacerbation in association with pesticide exposure - PS2619

It is proposed to carry out a systematic review of epidemiological studies of groups of individuals exposed to pesticides, including both those exposed at work (e.g. agricultural workers) and the general public (e.g. bystanders when pesticide application is taking place or via residential exposure). The aim of the review is to identify any associations between exposure to pesticides and the occurrence of respiratory symptoms and, in particular, the occurrence of asthma - both new cases of asthma and the exacerbation of existing symptoms of asthma. The work will involve first identifying published studies of relevant groups and then systematically reviewing each of the studies in detail to determine the strength of evidence for, or against, a relationship between pesticide exposure and respiratory ill health.

The review will include both agricultural and non-agricultural pesticides (e.g. biocides, veterinary medicines such as sheep dip). Issues conerning the tranferability of findings from non-UK studies and the relevance of the pesticides studied to current pesticide use in the UK will be examined.

The detailed reviews will consider issues such as the size of the study population, the nature and extent of pesticides exposure and how well this exposure has been characterised, potential exposure to other factors influencing respiratory health (e.g. smoking), and the health endpoints considered and how they were defined and measured. It is important, for example, that negative results in studies with inadequate exposure assessment or positive results in studies where individuals were exposed to other risk factors are not given undue importance in the overall assessment of risk.

Pesticides include a very wide range of chemicals and in order to better understand any potential relationship with respiratory health, the available studies will be organised into chemically related groups of pesticides, as it is unlikely that all pesticides will be associated with the same risk of respiratory symptoms. Groupings of pesticides will be based on previous work carried out by the contractoirs as part of the TEMPEST study which developed a task-based exposure matrix for pesticide exposure. An assessment will then be made of the strength of evidence linking each group of pesticides to respiratory ill health. A statistical meta-analysis, where appropriate, will form an important part of this assessment for groups of pesticides for which multiple studies are available. It is anticipated, however, that for many types of pesticides, insufficient studies will exist to enable such an analysis to be undertaken.The demonstration of a statistical relationship between respiratory illness and pesticide exposure in epidemiological studies would not necessarily mean that the relationship is causal, particularly if only a single study is available for a particular chemical class of pesticides. An important component of the study will be to investigate the biological plausibility and evidence for causality of any epidemiological relationships found.

The overall outcome of the review will include an assessment of the strength of evidence linking individual chemical groups of pesticides to respiratory ill health, an assessment of the magnitude of any health effects, identification of key gaps in the knowledge base and recommendations as to the further research required to fill these gaps.
1. Identification of published epidemiological studies of individuals exposed, occupationally or non-occupationally, to pesticides to determine the relationship, if any, between pesticide exposure and respiratory ill health;

2. Review of the strength of evidence linking pesticide exposure to respiratory ill health in individual studies, taking account of the characteristics of the exposure;

3. If sufficient data exist, identify specific pesticides or groups of chemically related pesticides that may be linked to respiratory ill health;

4. Undertake a meta-analysis, if warranted, to determine the overall strength of evidence linking specific groups of pesticides to respiratory ill health;

5. Review the biological plausibility and assess the evidence for causality of any apparent relationships between respiratory ill health and specific pesticides/groups of pesticides;

6. Advise on the current strength of evidence linking pesticide exposure to respiratory ill health

7. Identify the major gaps in the existing knowledge base and make recommendations on the research required to fill these gaps and how this research might be performed.

Project Documents
• FRP - Final Report : PS2619 Final report   (734k)
Time-Scale and Cost
From: 2010

To: 2011

Cost: £54,138
Contractor / Funded Organisations
Institute of Occupational Medicine
Environment and Health              
Hazardous substances              
Health Effects              
Operator Safety              
Pesticide use              
Public Health              
Sheep Dipping              
Veterinary Medicines              
Fields of Study
Pesticide Safety