Introduction: Childhood exposure to phthalates, a class of chemicals with known reproductive and developmental effects, may contribute to risk of obesity. Phthalate exposure occurs through multiple sources including contact with toys, food packaging, and personal care products. Our objective was to quantify the association between urinary phthalate metabolite concentrations and concurrently measured body mass index (BMI) in preschool aged children.
Methods: We collected anthropometric measures and biomonitoring data on approximately 200 children between ages two and five years of age enrolled in the Maternal-Infant Research on Environmental Chemicals Child Development Plus study. We measured 22 phthalate metabolites in urine; 20 had an adequate percent of samples above the limit of detection. Sixteen of these were summed into 5 distinct parent compounds. The remaining four metabolites originated from a unique parent compound and were modelled individually. Our primary exposures were, therefore, 5 parent compounds and 4 metabolites. Children’s weight and height were converted to BMI z-scores using the World Health Organization growth standards. We used linear regression, adjusted for maternal and child confounders, to evaluate associations between tertiles of phthalate concentrations and BMI z-scores. We stratified all analyses by sex and also tested for interactions between each phthalate metabolite or parent compound and sex.
Results: Our analytic sample included 189 singleton-born children with complete anthropometric data. Children with concentrations of the parent compound di-n-butyl phthalate (∑DnBP) in the third tertile (≥ 156 nnmol/L) had 0.475 (95% CI: 0.068, 0.883) higher BMI z-scores than those in the referent category (< 7.29 nmol/L). Effect modification by sex was observed in the model with the parent compound diisodecyl phthalate (∑DIDP) (p<0.05), yet no significant associations were observed in the sex-specific strata. No other significant associations were observed.
Conclusion: The observed association between childhood ∑DnBP exposure and BMI z-scores warrants confirmation in a study with serial phthalate measurements.
Linda Dodds– Professor, Dalhousie University
Tye Arbuckle– Research Scientist, Health Canada
Bruce Lanphear– Professor, Simon Fraser University
Gina Muckle– Professor, University of Laval
Warren Foster– Professor, McMaster University
Pierre Ayotte– Professor, Laval University
Angelika Zidek– Research Scientist, Health Canada
Stefan Kuhle– Associate Professor, Dalhousie University