[1] Brown Univ, Dept Epidemiol, Box G-S121, Providence, RI 02912 USA
[2] Brown Univ, Sch Publ Hlth, Dept Biostat, Providence, RI USA
[3] Univ Louisville, Dept Med, Div Environm Med, Louisville, KY 40292 USA
[4] Johns Hopkins Univ, Sch Publ Hlth, Dept Environm Hlth & Engn, Baltimore, MD USA
[5] Univ Cincinnati, Coll Med, Dept Pediat, Cincinnati, OH USA
[6] Univ Cincinnati, Cincinnati Childrens Hosp Med Ctr, Dept Radiol, Coll Med, Cincinnati, OH USA
[7] Univ Penn, Perelman Sch Med, Dept Biostat Epidemiol & Informat, Philadelphia, PA 19104 USA
[8] Brown Univ, Dept Family Med, Warren Alpert Med Sch, Providence, RI USA
[9] Kent Mem Hosp, Warwick, RI USA
[10] Cincinnati Childrens Hosp Med Ctr, Div Gastroenterol Hepatol & Nutr, Cincinnati, OH 45229 USA
[11] Brown Univ, Dept Pathol & Lab Med, Providence, RI 02912 USA
[12] Simon Fraser Univ, Fac Hlth Sci, Bumaby, BC, Canada