Residential pesticides and childhood leukemia: a systematic review and meta-analysis

Abstract

Objective: We conducted a systematic review and meta-analysis of previous observational epidemiologic studies examining the relationship between residential pesticide exposures during critical exposure time windows (preconception, pregnancy, and childhood) and childhood leukemia.

Data sources: Searches of MEDLINE and other electronic databases were performed (1950-2009). Reports were included if they were original epidemiologic studies of childhood leukemia, followed a case-control or cohort design, and assessed at least one index of residential/household pesticide exposure/use. No language criteria were applied.

Data extraction: Study selection, data abstraction, and quality assessment were performed by two independent reviewers. Random effects models were used to obtain summary odds ratios (ORs) and 95% confidence intervals (CIs).

Data synthesis: Of the 17 identified studies, 15 were included in the meta-analysis. Exposures during pregnancy to unspecified residential pesticides (summary OR = 1.54; 95% CI, 1.13-2.11; I2 = 66%), insecticides (OR = 2.05; 95% CI, 1.80-2.32; I2 = 0%), and herbicides (OR = 1.61; 95% CI, 1.20-2.16; I2 = 0%) were positively associated with childhood leukemia. Exposures during childhood to unspecified residential pesticides (OR = 1.38; 95% CI, 1.12-1.70; I2 = 4%) and insecticides (OR = 1.61; 95% CI, 1.33-1.95; I2 = 0%) were also positively associated with childhood leukemia, but there was no association with herbicides.

Conclusions: Positive associations were observed between childhood leukemia and residential pesticide exposures. Further work is needed to confirm previous findings based on self-report, to examine potential exposure-response relationships, and to assess specific pesticides and toxicologically related subgroups of pesticides in more detail.

Figure 1

Study selection.

Figure 2

Analysis of the association between childhood leukemia and exposure to (A) unspecified residential pesticides during pregnancy, (B) residential insecticides during pregnancy, and (C) residential herbicides during pregnancy. Squares indicating ORs from individual studies are proportional in size to the weight assigned to each estimate.

Figure 3

Analysis of the association between childhood leukemia and exposure to (A) unspecified residential pesticides during childhood, (B) residential insecticides during childhood, and (C) residential herbicides during childhood. Squares indicating ORs from individual studies are proportional in size to the weight assigned to each estimate.