[1] Department of Health Risk Analysis & Toxicology,
[2] Maastricht University,undefined
[3] P.O. Box 616,undefined
[4] 6200 MD Maastricht,undefined
[5] The Netherlands Fax: 31 43-3670924; E-mail: P.Borm@grat.unimaas.nl,undefined
[6] Department of Epidemiology and Public Health,undefined
[7] Wageningen Agricultural University,undefined
[8] The Netherlands,undefined