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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.

Motor Neurone Diseases (MND) are a group of progressive, irreversible, and terminal neurodegenerative diseases, with death usually resulting about three years after first symptoms of weakness. No cure is available. Whilst the aetiology of MND is largely unknown, some occupations, occupational exposures, and lifestyle factors have been associated with elevated risks, but evidence has been mixed. This thesis describes a case-control study that assessed associations with MND for a range of potentially modifiable risk factors, including specific occupations; occupational exposures (extremely low frequency-magnetic fields (ELF-MF), electric shocks, and a range of chemicals including pesticides); physical and emotional trauma; and leisure sports. A total of 321 cases and 605 population controls participated in the study. Elevated risks for MND were observed for several horticultural occupations, including field crop and vegetable growers, fruit growers, gardeners and nursery growers, crop and livestock producers. Employment as a builder, electrician, caregiver, forecourt attendant, plant and machine operator and assembler, and telecommunications technician was also positively associated with MND. Having ever worked in an occupation with potential for electric shocks was positively associated with MND, but no association was observed for occupational exposure to ELF-MF. Occupational exposure to pesticides, in particular insecticides, fungicides, and fumigants was associated with MND, with longer exposure duration associated with higher risk. Elevated odds for MND were also found for exposure to petrol/diesel fuel, unspecified solvents, disinfectants, and cleaning products. Having had multiple head injuries with concussion was associated with increased odds of MND; spine injury was not associated with MND. Playing sports throughout childhood and adulthood increased the risk of MND compared to never engaging in sports. Playing football (soccer) for >12 years was also positiv