Abstract
BACKGROUND: Residential use of pesticides has been associated with increased risk of childhood acute lymphoblastic leukemia (ALL). We evaluated determinants of glyphosate concentrations in house dust and estimated ALL risk in the California Childhood Leukemia Study (CCLS). METHODS: The CCLS is a population-based case-control study of childhood leukemia in California. Among those < 8-years (no move since diagnosis/reference date), we collected dust (2001-2007) from the room where the child spent the most time while awake and measured > 40 pesticides. Three-to-eight years later, we collected a second sample from non-movers. We used Ultra-Performance Liquid Chromatography Tandem Mass Spectrometry to measure glyphosate (µg/g dust) for 181 ALL cases and 225 controls and for 45 households with a second dust sample. We used multivariable Tobit regression to evaluate determinants of glyphosate concentrations. Odds ratios (ORs) and 95 % confidence intervals (CI) were calculated for ALL and quartiles of the concentration (first samples) using unconditional logistic regression. We computed the within- and between-home variance and intraclass correlation coefficient (ICC). RESULTS: Glyphosate was frequently detected (cases: 98 %; controls: 99 %). Higher concentrations were associated with occupational pesticide exposure, nearby agricultural use, treatment for lawn weeds and bees/wasps, and sampling season. Increasing concentrations were not associated with ALL risk (adjusted OR(Q4vsQ1) = 0.8, CI: 0.4-1.4). We observed similar null associations for boys and girls, Hispanics and non-Hispanic whites, and among those who resided in their home since birth (76 cases/117 controls) or age two (130 cases/176 controls). The ICC was 0.32 indicating high within-home temporal variability during the years of our study. CONCLUSIONS: We observed higher concentrations in homes associated with expected predictors of exposure but no association with childhood ALL risk. Due to continuing use, potential exposure to young children is high. It will be important to evaluate risk in future studies with multiple dust measurements or biomarkers of exposure.