Household exposure to pesticides and risk of leukemia in children and adolescents: Updated systematic review and meta-analysis.

BACKGROUND: The role that pesticides in the domestic environment might play in the etiology of childhood leukemia remains a subject of controversy. Recent studies often reached inconsistent conclusions.

OBJECTIVE: To update our earlier systematic review on the association between residential/household/domestic exposure to pesticides and childhood leukemia, and to explore potential sources of heterogeneity not previously assessed.

METHODS: A systematic search of studies published in English between January 2009 and June 2018 was conducted in MEDLINE, and a "snowball searching" was performed from the reference list of identified publications and from Web of Science citations. Risk estimates were extracted from 15 case-control studies published between 1987 and 2018. The quality of the publications was assessed by using a modified version of the Downs and Black (1998) checklist. A random-effect meta-analysis model was used to calculate summary odds ratios (SOR) and separate analyses were conducted for acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), unspecified AL/leukemia and any leukemia types. Stratification by critical exposure period, exposure location, pesticide biocide category, child age at diagnosis, study quality, specific exposures, type of pest treated, and geographic location were performed.

RESULTS: A statistically significant association between residential pesticide exposure and childhood leukemia was observed by combining all studies (SOR: 1.57; 95% CI: 1.27-1.95) without evidence of publication bias. Statistically significant increased risks were observed for all types of leukemia, and specifically for exposure during pregnancy, indoor exposure, prenatal exposure to insecticides and whatever the age at diagnosis. Statistical significance was also reached for high quality studies, pet treatments, professional pest control treatment and use of insect repellants, mosquito treatment and for studies from USA/Canada or International. The highest increased risks were observed for AML among children aged 2 years or less, as well as for unspecified leukemia type observed after prenatal indoor exposure.

CONCLUSIONS: A positive association between domestic pesticide exposure and childhood leukemia is confirmed. Although the literature provides moderate to low-quality of evidence, these new results further justify the need of limiting the use of household pesticides during pregnancy and childhood.