[1] Univ Nevada, Dept Environm & Occupat Hlth, Las Vegas Sch Publ Hlth, 4700 S Maryland Pkwy,Suite 335,MS 3063, Las Vegas, NV 89119 USA
[2] Univ Cincinnati, Dept Environm Hlth, Div Epidemiol, Coll Med, POB 670056, Cincinnati, OH 45267 USA
[3] Univ Cincinnati, Cincinnati Childrens Hosp Med Ctr, Dept Pediat, Div Gen & Community Pediat,Coll Med, 3333 Burnet Ave,MLC 7035, Cincinnati, OH 45229 USA
[4] Brown Univ, Dept Epidemiol, Sch Publ Hlth, 121 South Main St,Box G-S121-2, Providence, RI 02912 USA
[5] Ctr Dis Control & Prevent, Natl Ctr Environm Hlth, Div Lab Sci, Atlanta, GA 30341 USA
[6] Simon Fraser Univ, BC Childrens Hosp, Res Inst, 8888 Univ Dr, Burnaby, BC V5A 1S6, Canada
[7] Simon Fraser Univ, Fac Hlth Sci, 8888 Univ Dr, Burnaby, BC V5A 1S6, Canada
[8] Univ Penn, Perelman Sch Med, Dept Biostat Epidemiol & Informat, 423 Guardian Dr,Blockley Hall 231, Philadelphia, PA 19104 USA