[1] US EPA, HLTH EFFECTS RES LAB, DIV BIOMETRY, BIOSTAT BRANCH, RES TRIANGLE PK, NC 27711 USA
[2] UNIV N CAROLINA, SCH MED, CTR ENVIRONM MED & LUNG BIOL, CHAPEL HILL, NC 27514 USA
[3] WAKE FOREST UNIV, BOWMAN GRAY SCH MED, DEPT MED, RHEUMATOL SECT, WINSTON SALEM, NC 27103 USA