Academic journal article Environmental Health Perspectives

A Systematic Review and Meta-Analysis of Childhood Leukemia and Parental Occupational Pesticide Exposure

Academic journal article Environmental Health Perspectives

A Systematic Review and Meta-Analysis of Childhood Leukemia and Parental Occupational Pesticide Exposure

Article excerpt

OBJECTIVES: We conducted a systematic review and meta-analysis of childhood leukemia and parental occupational pesticide exposure.

DATA SOURCES: Searches of MEDLINE (1950-2009) and other electronic databases yielded 31 included studies.

DATA EXTRACTION: Two authors independently abstracted data and assessed the quality of each study.

DATA SYNTHESIS: Random effects models were used to obtain summary odds ratios (ORs) and 95% confidence intervals (CIs). There was no overall association between childhood leukemia and any paternal occupational pesticide exposure (OR = 1.09; 95% CI, 0.88-1.34); there were slightly elevated risks in subgroups of studies with low total-quality scores (OR = 1.39; 95% CI, 0.99-1.95), ill-defined exposure time windows (OR = 1.36; 95% CI, 1.00-1.85), and exposure information collected after offspring leukemia diagnosis (OR = 1.34; 95% CI, 1.05-1.70). Childhood leukemia was associated with prenatal maternal occupational pesticide exposure (OR = 2.09; 95% CI, 1.51-2.88); this association was slightly stronger for studies with high exposure-measurement-quality scores (OR = 2.45; 95% CI, 1.68-3.58), higher confounder control scores (OR = 2.38; 95% CI, 1.56-3.62), and farm-related exposures (OR = 2.44; 95% CI, 1.53-3.89). Childhood leukemia risk was also elevated for prenatal maternal occupational exposure to insecticides (OR = 2.72; 95% CI, 1.47-5.04) and herbicides (OR = 3.62; 95% CI, 1.28-10.3).

CONCLUSIONS: Childhood leukemia was associated with prenatal maternal occupational pesticide exposure in analyses of all studies combined and in several subgroups. Associations with paternal occupational pesticide exposure were weaker and less consistent. Research needs include improved pesticide exposure indices, continued follow-up of existing cohorts, genetic susceptibility assessment, and basic research on childhood leukemia initiation and progression.

KEY WORDS: child, leukemia, meta-analysis, occupational exposure, pesticides. Environ Health Perspect 117:1505-1513 (2009). doi:10.1289/ehp.0900582 available via http://dx.doi.org/ [Online 19 May 2009]

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Although leukemia is the most common childhood cancer, the only established modifiable risk factor is prenatal or childhood exposure to ionizing radiation (Belson et al. 2007; Doll and Wakeford 1997). Acute lymphocytic leukemia (ALL) comprises about 80% of all childhood leukemia cases, the remainder being mainly acute myeloid leukemia (AML) (Borugian et al. 2005). All known risk factors, including ionizing radiation, sex, race, Down syndrome, and other genetic syndromes, account for < 10% of all childhood leukemia cases (Buffler et al. 2005). A narrative review concluded that recent epidemiologic studies are consistent with those reviewed previously (Zahm and Ward 1998) and support associations between childhood leukemia and parental pesticide exposure before and during pregnancy and childhood exposure to household insecticides (Infante-Rivard and Weichenthal 2007). In a recent meta-analysis, childhood leukemia was weakly associated with preconceptual and overall paternal smoking (Lee et al. 2009). Other potential risk factors include preconceptual paternal occupational exposure to solvents (Buckley et al. 1989), motor exhaust fumes (Vianna et al. 1984), or electromagnetic fields (Feychting et al. 2000; Pearce et al. 2007); prenatal maternal alcohol consumption (for AML) (Shu et al. 1996); and reduced occurrence of common infections during childhood (Ma et al. 2005). Prenatal maternal occupational electromagnetic field exposure was linked to childhood leukemia in a Canadian case-control study (Infante-Rivard and Deadman 2003) but not in two other case-control studies (Feychting et al. 2000; Sorahanetal. 1999).

Preconceptual paternal occupational or environmental exposures have not been established as causes of any childhood cancer. Although prenatal maternal exposure to ionizing radiation can cause childhood leukemia, there is little evidence that preconceptual paternal ionizing radiation exposure is a risk factor (Draper et al. …

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