Leukemia among New Zealand agricultural workers. A cancer registry-based study.

Mortality studies have indicated that workers in agriculture and forestry may be at increased risk of leukemia. Findings are reported from a New Zealand Cancer Registry-based case-control study involving 546 male leukemia patients registered during 1979-1983 and aged 20 years or more at time of registration. Controls were also males chosen from the Cancer Registry with four controls per case, matched on age and year of registration. The case group contained an excess of the occupational category involving agriculture and forestry (odds ratio (OR) = 1.24, 95% confidence interval (CI) = 0.95-1.61) with the greatest relative risk being for livestock farmers (OR = 3.00, 95% CI = 1.23-7.32). There was also an excess of electrical workers (OR = 1.72, 95% CI = 0.92-3.20). The agricultural excess was greatest in patients aged 65 years or more at time of registration (OR = 1.29, 95% CI = 0.94-1.78), particularly in patients with acute myeloid leukemia (OR = 1.55, 95% CI = 0.90-2.67) or acute monocytic leukemia OR = 10.38, 95% CI = 1.99-54.29), although the latter excess only involved five cases. Acute myeloid leukemia was also elevated in meat workers (OR = 2.51, 95% CI = 1.19-5.30).