[1] Texas Dept State Hlth Serv, Austin, TX USA
[2] Baylor Coll Med, Houston, TX 77030 USA
[3] NIOSH, Cincinnati, OH 45226 USA
[4] Univ N Carolina, Chapel Hill, NC USA
[5] Stanford Univ, Sch Med, Palo Alto, CA 94304 USA
[6] Univ Iowa, Iowa City, IA USA
[7] Univ Texas Houston, Sch Publ Hlth, Houston, TX USA
[8] Ctr Dis Control & Prevent, Atlanta, GA USA
[9] Univ Arkansas Med Sci, Little Rock, AR 72205 USA