Fathers' occupational contacts and risk of childhood leukemia and non-hodgkin lymphoma.

BACKGROUND: There is evidence to suggest that childhood leukemia and non-Hodgkin lymphoma have an infective etiology. We investigated the risk of childhood leukemia and non-Hodgkin lymphoma in relation to paternal occupational contact with other individuals, a surrogate for potential exposure to infection.
METHODS: We carried out a case-control study using 792 cases from the Northern Region Young Persons' Malignant Disease Registry, United Kingdom, 1968-1997, and 2 large population-based control groups. Paternal occupations at birth were classified as having standard, high, or very high levels of contact. Conditional logistic regression was used in the analysis.
RESULTS: There was an increased risk of childhood leukemia and non-Hodgkin lymphoma in those children whose fathers' occupational contacts were high or very high compared with standard (odds ratio = 1.3; 95% confidence interval = 1.0-1.5). The excess risk in the very high group was most pronounced for 245 cases of acute lymphoblastic leukemia aged 2 to 5 years at diagnosis (1.5; 1.1-2.1). The risk with paternal occupational contacts was greater in rural areas, although it was also present in urban areas. The risks of leukemia and non-Hodgkin lymphoma were also higher among the offspring of men employed as policemen, sales representatives, or teachers.
CONCLUSIONS: Our findings are consistent with the hypothesis of an infective etiology for childhood leukemia and non-Hodgkin lymphoma, and they add to the evidence that infections could be transmitted to children by adults.