(Beyond Pesticides, August 28, 2007) In a new study published in the August 2007 issue of the Scandinavian Journal of Work, Environment and Health (Vol. 33, No. 4), researchers from the Central American Institute for Studies on Toxic Substances (IRET) in Costa Rica find parental exposure to pesticides linked to the increased risk of leukemia. IRET researchers, based at the National University of Costa Rica in Heredia, identified cases of childhood leukemia (N=334), in 1995-2000, on the Cancer Registry and the Children’s Hospital. Population controls (N=579) were drawn from the National Birth Registry. Interviews of parents were conducted using conventional and icon-based calendar forms. An exposure model was constructed for 25 pesticides in five time periods.
Mothers’ exposures to any pesticides during the year before conception and during the first and second trimesters are associated with the risk [odds ratio (OR) 2.4, 95% confidence interval (95% CI) 1.0-5.9; OR 2.2, 95% CI 2.8-171.5; OR 4.5, 95% CI 1.4-14.7, respectively] and during anytime (OR 2.2, 95% CI 1.0-4.8). An association is found for fathers’ exposures to any pesticides during the second trimester (OR 1.5, 95% CI 1.0-2.3).
An increased risk with respect to organophosphates is found for mothers during the first trimester (OR 3.5, 95% CI 1.0-12.2) and for fathers during the year before conception and the first trimester (OR 1.5, 95% CI 1.0-2.2 and OR 1.6, 95% CI 1.0-2.6, respectively), and benzimidazoles during the first, second, and third trimesters of pregnancy (OR 2.2, 95% CI 1.0-4.4; OR 2.2, 95% CI 1.0-5.0; OR 2.2, 95% CI 1.0-5.2, respectively).
There is a suggestion of an exposure-response gradient for fathers as regards picloram, benomyl, and paraquat. Age at diagnosis was positively associated with fathers’ exposures and inversely associated with mothers’ exposures.
Leukemias are the most common childhood cancers, accounting for 25-35% of the incidence of all childhood cancer in most populations. Costa Rica ranks among the highest incidence of childhood leukemia in the world. Agriculture is a major economic activity in Costa Rica and is characterized by intensive use of pesticides.
Previous studies have also linked parental exposure to leukemia. A 2006 French study published in the journal Occupational and Environmental Medicine, “Household Exposure to Pesticides and Risk of Childhood Acute Leukemia,” indicates that acute leukemia is observed to be significantly associated with maternal home pesticide use during pregnancy along with lawn chemical use and fungicide use during childhood. Research findings also show insecticidal shampoo treatment of pediculosis to be associated with childhood acute leukemia. Leukemia has also been linked to parental exposure to Agent Orange in children of Vietnam veterans.