Browsing by Author "Ayotte, Pierre"

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    ADDENDUM: Critical windows of fluoride neurotoxicity in Canadian Children
    (Elsevier, 2022) Farmus, Linda; Till, Christine; Green, Rivka; Hornung, Richard; Martinez Mier, E. Angeles; Ayotte, Pierre; Muckle, Gina; Lanphear, Bruce P.; Flora, David B.; Dental Public Health and Dental Informatics, School of Dentistry
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    Associations between Urinary, Dietary, and Water Fluoride Concentrations among Children in Mexico and Canada
    (MDPI, 2020-11-08) Green, Rivka; Till, Christine; Cantoral, Alejandra; Lanphear, Bruce; Martinez-Mier, E. Angeles; Ayotte, Pierre; Wright, Robert O.; Tellez-Rojo, Martha M.; Malin, Ashley J.; Cariology, Operative Dentistry and Dental Public Health, School of Dentistry
    Fluoride, which may be toxic to the developing brain, is added to salt in Mexico and drinking water in Canada to prevent dental caries. We compared childhood urinary fluoride (CUF) concentrations in Mexico City and Canada to characterize patterns of fluoride exposure in these two populations. We also examined associations of CUF with dietary and water fluoride levels in Mexico City and Canada respectively. We included 561 children (ages 4–6; mean age 4.8 years) from the Programming Research in Obesity, Growth, Environment, and Social Stress (PROGRESS) cohort in Mexico City, and 645 children (ages 2–6; mean age 3.7 years) from the Maternal–Infant Research on Environmental Chemicals (MIREC) cohort in Canada. We applied Spearman correlations, T-tests, ANOVA or covariate-adjusted linear regression to examine associations of CUF (mg/L; adjusted for specific gravity) with demographics and dietary or water fluoride concentrations. We used Welch equivalence testing to compare means across cohorts. Mean (SD) CUF was equivalent (t = 4.26, p < 0.001) in PROGRESS: 0.74 (0.42) and fluoridated Canadian communities: 0.66 (0.47), but lower in non-fluoridated Canadian communities: 0.42 (0.31) (t = −6.37, p < 0.001). Water fluoride concentrations were significantly associated with CUF after covariate adjustment for age and sex in MIREC (B = 0.44, 95% CI: 0.30, 0.59, p < 0.001). In contrast, daily food and beverage fluoride intake was not associated with CUF in PROGRESS (p = 0.82). We found that CUF levels are comparable among children in Mexico City and fluoridated Canadian communities, despite distinct sources of exposure. Community water fluoridation is a major source of fluoride exposure for Canadian children.
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    Critical windows of fluoride neurotoxicity in Canadian children
    (Elsevier, 2021) Farmus, Linda; Till, Christine; Green, Rivka; Hornung, Richard; Martinez Mier, E. Angeles; Ayotte, Pierre; Muckle, Gina; Lanphear, Bruce P.; Flora, David B.; Dental Public Health and Dental Informatics, School of Dentistry
    Background: Fluoride has been associated with IQ deficits during early brain development, but the period in which children are most sensitive is unknown. Objective: We assessed effects of fluoride on IQ scores across prenatal and postnatal exposure windows. Methods: We used repeated exposures from 596 mother-child pairs in the Maternal-Infant Research on Environmental Chemicals pregnancy and birth cohort. Fluoride was measured in urine (mg/L) collected from women during pregnancy and in their children between 1.9 and 4.4 years; urinary fluoride was adjusted for specific gravity. We estimated infant fluoride exposure (mg/day) using water fluoride concentration and duration of formula-feeding over the first year of life. Intelligence was assessed at 3-4 years using the Wechsler Preschool and Primary Scale of Intelligence-III. We used generalized estimating equations to examine the associations between fluoride exposures and IQ, adjusting for covariates. We report results based on standardized exposures given their varying units of measurement. Results: The association between fluoride and performance IQ (PIQ) significantly differed across prenatal, infancy, and childhood exposure windows collapsing across child sex (p = .001). The strongest association between fluoride and PIQ was during the prenatal window, B = -2.36, 95% CI: -3.63, -1.08; the association was also significant during infancy, B = -2.11, 95% CI: -3.45, -0.76, but weaker in childhood, B = -1.51, 95% CI: -2.90, -0.12. Within sex, the association between fluoride and PIQ significantly differed across the three exposure windows (boys: p = .01; girls: p = .01); among boys, the strongest association was during the prenatal window, B = -3.01, 95% CI: -4.60, -1.42, whereas among girls, the strongest association was during infancy, B = -2.71, 95% CI: -4.59, -0.83. Full-scale IQ estimates were weaker than PIQ estimates for every window. Fluoride was not significantly associated with Verbal IQ across any exposure window. Conclusion: Associations between fluoride exposure and PIQ differed based on timing of exposure. The prenatal window may be critical for boys, whereas infancy may be a critical window for girls.
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    Iodine Status Modifies the Association between Fluoride Exposure in Pregnancy and Preschool Boys' Intelligence
    (MDPI, 2022-07-16) Goodman, Carly V.; Hall, Meaghan; Green, Rivka; Chevrier, Jonathan; Ayotte, Pierre; Martinez-Mier, Esperanza Angeles; McGuckin, Taylor; Krzeczkowski, John; Flora, David; Hornung, Richard; Lanphear, Bruce; Till, Christine; Cariology, Operative Dentistry and Dental Public Health, School of Dentistry
    In animal studies, the combination of in utero fluoride exposure and low iodine has greater negative effects on offspring learning and memory than either alone, but this has not been studied in children. We evaluated whether the maternal urinary iodine concentration (MUIC) modifies the association between maternal urinary fluoride (MUF) and boys' and girls' intelligence. We used data from 366 mother-child dyads in the Maternal-Infant Research on Environmental Chemicals Study. We corrected trimester-specific MUF and MUIC for creatinine, and averaged them to yield our exposure variables (MUFCRE, mg/g; MUICCRE, µg/g). We assessed children's full-scale intelligence (FSIQ) at 3 to 4 years. Using multiple linear regression, we estimated a three-way interaction between MUFCRE, MUICCRE, and child sex on FSIQ, controlling for covariates. The MUICCRE by MUFCRE interaction was significant for boys (p = 0.042), but not girls (p = 0.190). For boys whose mothers had low iodine, a 0.5 mg/g increase in MUFCRE was associated with a 4.65-point lower FSIQ score (95% CI: -7.67, -1.62). For boys whose mothers had adequate iodine, a 0.5 mg/g increase in MUFCRE was associated with a 2.95-point lower FSIQ score (95% CI: -4.77, -1.13). These results suggest adequate iodine intake during pregnancy may minimize fluoride's neurotoxicity in boys.