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.
- 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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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.
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