[1] Brown Univ, Dept Epidemiol, Providence, RI USA
[2] Cincinnati Childrens Hosp Med Ctr, Dept Pediat, Div Gen & Community Pediat, Cincinnati, OH 45229 USA
[3] Ctr Dis Control & Prevent, Natl Ctr Environm Hlth, Div Sci Lab, Atlanta, GA USA
[4] Univ Cincinnati, Coll Med, Dept Environm Hlth, Div Epidemiol & Biostat, Cincinnati, OH 45267 USA
[5] Simon Fraser Univ, BC Childrens & Womens Hosp, Child & Family Res Inst, Vancouver, BC, Canada
[6] Simon Fraser Univ, Fac Hlth Sci, Vancouver, BC, Canada
[7] Univ Rochester, Sch Med, Dept Pediat, New York, NY USA