(Beyond Pesticides, December 6, 2007)
A study published in Environmental Health Perspectives this month finds that children born to mothers living in households with pesticide use during pregnancy have over twice as much risk of getting cancer, specifically acute leukemia (AL) or non-Hodgkin lymphoma (NHL). The study, Household Exposure to Pesticides and Risk of Childhood Hematopoietic Malignancies: The ESCALE Study (SFCE), 115:1787-1793 (2007), investigates the role of household exposure to pesticides in the etiology of childhood hematopoietic malignancies, using the national registry-based case-control study ESCALE (Etude sur les cancers de l’enfant) that was carried out in France over the period 2003-2004.
The researchers evaluated maternal household use of pesticides during pregnancy and paternal use during pregnancy or childhood which was reported by the mothers in a structured telephone questionnaire. Insecticides (used at home, on pets or for garden crops), herbicides and fungicides were distinguished. The researchers estimated odds ratios (ORs) using unconditional regression models closely adjusting for age, sex, degree of urbanization, and type of housing (flat or house).
The researchers included a total of 764 cases of acute leukemia (AL), 130 of Hodgkin lymphoma (HL), 166 of non-Hodgkin lymphoma (NHL), and 1,681 controls. Insecticide use during pregnancy was significantly associated with childhood AL [OR = 2.1; 95% confidence interval (CI), 1.7-2.5], both lymphoblastic and myeloblastic, NHL (OR = 1.8; 95% CI, 1.3-2.6), mainly for Burkitt lymphoma (OR = 2.7; 95% CI, 1.6-4.5), and mixed-cell HL (OR = 4.1; 95% CI, 1.4-11.8).
The researchers conclude that the study findings strengthen the hypothesis that domestic use of pesticides may play a role in the etiology of childhood hematopoietic malignancies. The consistency of the findings with those of previous studies on AL raises the question of the advisability of preventing pesticide use by pregnant women.
Hematopoietic malignancies are the most common childhood cancers, with world age-standardized incidence rates of 43.1, 6.7, and 8.9 per million children in France for leukemia, Hodgkin lymphoma (HL), and non-Hodgkin lymphoma (NHL), respectively (Clavel et al. 2004). The etiology of those malignancies remains largely unknown. Some epidemiologic studies have suggested that pesticides might increase the risk of childhood hematopoietic malignancies (Daniels et al. 1997; Infante-Rivard and Scott Weichenthal 2007; Jurewicz and Hanke 2006; Nasterlack 2006, 2007; Zahm and Ward 1998). Furthermore, the International Agency for Research on Cancer (IARC) has classified the occupational spraying of insecticides as probably carcinogenic to humans (group 2A); adult lymphoma is one of the main cancers suspected (IARC 1991). Children can be exposed to pesticides in utero or during childhood through their parents’ work, domestic use, or the general environment (residues in food, water, air, and soil). It is not clear which sources of pesticide exposure are the most important for children, and household pesticide exposure may be a major exposure for children (Bradman and Whyatt 2005; Grossman 1995). No French survey on household pesticide use is available, but surveys conducted in North America and the United Kingdom reported high rates of household use or storage of pesticides (Adgate et al. 2000; Grey et al. 2006).
This study supports numerous other studies that have for years linked household use of pesticides with elevated rates of childhood cancers. See [viii] Gold, E. et al., “Risk Factors for Brain Tumors in Children,” American Journal of Epidemiology 109(3): 309-319, 1979 and [ix] Lowengart, R. et al., “Childhood Leukemia and Parent’s Occupational and Home Exposures,” Journal of the National Cancer Institute 79:39, 1987.