1. Epidemiology Department, University of North Carolina, Chapel Hill, NC 27599-7315, USA
2. Institute of Experimental Medicine, Academy of Sciences of the Czech Republic and Regional Institute of Hygiene of Central Bohemia, Videnska 1083, 142 20 Prague, Czech Republic
3. Department of Pharmacology and Toxicology, University of Louisville, Louisville, KY 40292, USA
4. National Health and Environmental Effects Research Laboratory, US EPA, Research Triangle Park, NC 27711, USA