[1] Harvard Pilgrim Hlth Care Inst, Dept Populat Med, Boston, MA USA
[2] Harvard Univ, Sch Med, Boston, MA USA
[3] Harvard Univ, Sch Publ Hlth, Dept Environm Hlth, Boston, MA 02115 USA
[4] Dartmouth Med Sch, Dept Community & Family Med, Sect Biostat & Epidemiol, Lebanon, NH USA
[5] Washington State Dept Hlth, Olympia, WA USA
[6] Toulouse Sch Econ, Inst Natl Rech Agron, Lab Econ Ressources Nat, Toulouse, France
[7] US EPA, Washington, DC 20460 USA
[8] Harvard Univ, Brigham & Womens Hosp, Sch Med, Channing Lab,Dept Med, Boston, MA 02115 USA