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Original research
Occupational exposures to pesticides and other chemicals: a New Zealand motor neuron disease case–control study
  1. Grace Xia Chen1,
  2. J Douwes1,
  3. Leonard van den Berg2,
  4. Neil Pearce3,
  5. Hans Kromhout4,
  6. Bill Glass1,
  7. David J McLean1,
  8. Andrea Martine 't Mannetje1
  1. 1 Research Centre for Hauora and Health (formerly the Centre for Public Health Research), Massey University, Wellington, New Zealand
  2. 2 Department of Neurology, University Medical Centre Utrecht Brain Centre, Utrecht, The Netherlands
  3. 3 Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, UK
  4. 4 Institute for Risk Assessment Sciences, Utrecht University Institute for Risk Assessment Sciences, Utrecht, The Netherlands
  1. Correspondence to Ms Grace Xia Chen, Research Centre for Hauora and Health (formerly the Centre for Public Health Research), Massey University, Wellington, Wellington, New Zealand; g.chen1{at}


Objectives To assess associations between occupational exposures to pesticides and other chemicals and motor neuron disease (MND).

Methods A population-based case–control study that included 319 MND cases (64% male/36% female) recruited through the New Zealand MND Association complemented with hospital discharge data, and 604 controls identified from the Electoral Roll. For each job held, a questionnaire collected information on 11 exposure categories (dust, fibres, tobacco smoke, fumes, gas, fumigants, oils/solvents, acids/alkalis, pesticides, other chemicals and animals/animal products). ORs were estimated using logistic regression adjusting for age, sex, ethnicity, socioeconomic status, education, smoking, alcohol consumption, physical activities, head/spine injury and other occupational exposures.

Results Two exposure categories were associated with increased MND risks: pesticides (OR 1.70, 95% CI 1.17 to 2.48) and fumigants (OR 3.98, 95% CI 1.81 to 8.76), with risks increasing with longer exposure duration (p<0.01). Associations were also observed for: methyl bromide (OR 5.28, 95% CI 1.63 to 17.15), organochlorine insecticides (OR 3.28, 95% CI 1.18 to 9.07), organophosphate insecticides (OR 3.11, 95% CI 1.40 to 6.94), pyrethroid insecticides (OR 6.38, 95% CI 1.13 to 35.96), inorganic (copper) fungicides (OR 4.66, 95% CI 1.53 to 14.19), petrol/diesel fuel (OR 2.24, 95% CI 1.27 to 3.93) and unspecified solvents (OR 1.91, 95% CI 1.22 to 2.99). In women, exposure to textile fibres (OR 2.49, 95% CI 1.13 to 5.50), disinfectants (OR 9.66, 95% CI 1.29 to 72.44) and cleaning products (OR 3.53, 95% CI 1.64 to 7.59) were also associated with MND; this was not observed in men (OR 0.80, 95% CI 0.44 to 1.48; OR 0.72, 95% CI 0.29 to 1.84; OR 0.57, 95% CI 0.21 to 1.56, respectively).

Conclusions This study adds to the evidence that pesticides, especially insecticides, fungicides, and fumigants, are risk factors for MND.

  • pesticides
  • epidemiology
  • chemical hazard release
  • risk assessment
  • environmental exposure

Data availability statement

All data relevant to the study are included in the article or uploaded as supplemental information.

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Data availability statement

All data relevant to the study are included in the article or uploaded as supplemental information.

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  • Contributors DMcL, AM’tM, JD, NP, HK and LvdB contributed to the idea and design of the study. GXC was involved in all aspects of data collection, subsequent analyses, writing the first draft manuscript and is the guarantor of the article. DMcL, AM’tM, JD and BG reviewed the first draft and wrote parts of subsequent drafts. All authors provided critical feedback throughout the study and contributed to the final version of the manuscript.

  • Funding The study was funded by a grant from the Health Research Council (HRC) of New Zealand (Part of 11/1041 HRC Programme Grant - Building Research in Occupational Health in New Zealand (BROHNZ)).

  • Competing interests None declared.

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

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.