[1] NIOSH, Bioanalyt Branch, Hlth Effects Lab Div, Morgantown, WV USA
[2] Univ Washington, Dept Biostat, Seattle, WA 98195 USA
[3] Suny Downstate Med Ctr, Sch Publ Hlth, Dept Environm & Occupat Hlth Sci, New York, NY USA
[4] Wake Forest Univ, Bowman Gray Sch Med, Dept Social Sci & Hlth Policy, Publ Hlth Sci Div, Winston Salem, NC USA