Objectives After a successful feasibility study in 1996-97, the Health & Safety Executive established the Pesticide Users Health Study (PUHS) to monitor the health of workers occupationally exposed to pesticides in Great Britain. The history and findings of the PUHS are presented, and its future is outlined.

Methods Individuals applying for a certificate of competence in the use of agricultural pesticides were recruited. Cancer and death events in the cohort were flagged from the national health information system. A survey of pesticide usage was conducted in a small proportion of the cohort. Findings from the PUHS are compared with other well-established cohort studies internationally, and methodological challenges are discussed.

Results By 2003, nearly 66 000 men and women were members of the PUHS. Standardised incidence and mortality ratios (SIR/SMR) for cancers and deaths showed that overall these individuals were healthier than the British population (SIR all cancers: 0.86, 95% CI 0.81 to 0.90; SMR all causes: 0.58, 95% CI 0.55 to 0.61). There was weak evidence of elevated risks for some cancers. The PUHS findings were consistent with similar studies in the US. There was limited information to adjust for the Healthy Worker Effect and insufficient exposure data to interpret the findings.

Conclusions The PUHS is a valuable resource, providing a foundation upon which to develop a nationally representative prospective study of British pesticide users. A systematic approach to the assessment of baseline and follow-up pesticide usage, confounding factors, health symptoms and conditions, and other more detailed substudies are proposed. © Crown Copyright 2011.