1. Exposure Assessment Branch/NIOSH/CDC, Morgantown, West Virginia, USA
2. Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA
3. Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
4. Forest Products Laboratory, USDA Forest Service, Madison, Wisconsin, USA
5. Finnish Institute of Occupational Health, Helsinki, Finland
6. Department of Physiology & Pharmacology, School of Medicine/WVU, Morgantown, West Virginia, USA