[1] Univ Lund Hosp, Dept Occupat & Environm Med, S-22185 Lund, Sweden
[2] Univ Hosp No Sweden, Dept Occupat & Environm Med, Umea, Sweden
[3] Karolinska Inst, Ctr Nutr & Toxicol, S-10401 Stockholm, Sweden
[4] Natl Inst Working Life, Div Analyt Chem, Umea, Sweden
[5] Univ Stockholm, Dept Analyt Chem, Stockholm, Sweden
[6] Sundsvall Hosp, Dept Occupat & Environm Med, Sundsvall, Sweden