BMJ Open 1:e000283 doi:10.1136/bmjopen-2011-000283
  • Epidemiology
    • Research

Mortality from Parkinson's disease and other causes among a workforce manufacturing paraquat: a retrospective cohort study

  1. Clive Campbell2
  1. 1Causation Ltd, Macclesfield, UK
  2. 2Syngenta International AG, Basel, Switzerland
  1. Correspondence to Dr John Andrew Tomenson; john_tomenson{at}
  • Received 29 July 2011
  • Accepted 13 September 2011
  • Published 27 October 2011


Objective To assess the risk of Parkinson's disease (PD) and update information on mortality from major causes of death among a UK workforce who manufactured paraquat (PQ) between 1961 and 1995. There have been no previous studies of the incidence of PD among PQ production workers, although much epidemiological literature exists concerning the relationship between pesticides and PD, and interest has focused on PQ and its users.

Methods The cohort included all employees who had ever worked on any of the four plants at Widnes where PQ was manufactured between 1961 and 1995, and 926 male and 42 female workers were followed through 30 June 2009. Mortalities for males were compared with national and local rates, including rates for PD as a mentioned cause of death.

Results Overall, 307 workers had died by 30 June 2009. One male death was due to PD, and no other death certificate mentioned PD. At least 3.3 death certificates of male employees would have been expected to have mentioned PD (standardised mortality ratio=31; 95% CI 1 to 171). Personal monitoring results were indicative that the exposure of a PQ production worker on a daily basis was at least comparable with that of a PQ sprayer or mixer/loader. Reduced mortalities compared with local rates were found for major causes of death.

Conclusions The study provided no evidence of an increased risk of PD, or increased mortalities from other causes.


  • Correction notice The “To cite: …” information and running footer in this article have been updated with the correct volume number (volume 1).

  • To cite: Tomenson JA, Campbell C. Mortality from Parkinson's disease and other causes among a workforce manufacturing paraquat: a retrospective cohort study. BMJ Open 2011;1:e000283. doi:10.1136/bmjopen-2011-000283

  • Funding Syngenta funded this investigation.

  • Competing interests Both authors have completed the ICMJE uniform disclosure form at (available on request from the corresponding author) and declare: JAT had financial support from Syngenta for the submitted work; CC is employed by Syngenta; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethics approval Ethics approval was provided by the British Medical Association Ethical Committee.

  • Contributors JAT and CC conceived and designed the study. JAT wrote the protocol, supervised the acquisition of data, performed the data analyses and interpreted the results. Both authors contributed to drafting of the manuscript, critically reviewed the manuscript for important intellectual content and approved the final version of the paper.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement No additional data available.

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