[1] Ctr Dis Control & Prevent, Natl Ctr Hlth Stat, Hyattsville, MD 20782 USA
[2] US PHS, Rockville, MD USA
[3] NIEHS, Div Intramural Res, NIH, POB 12233, Res Triangle Pk, NC 27709 USA
[4] UCONN Hlth Farmington, Dept Pediat, Farmington, CT USA
[5] Connecticut Childrens Med Ctr, Hartford, CT USA
[6] Social & Sci Syst, Durham, NC USA
[7] Virginia Commonwealth Univ, Dept Family Med & Populat Hlth, Richmond, VA USA
[8] NIOSH, Ctr Dis Control & Prevent, Morgantown, WV USA