Affiliation: | (1) Norwegian Institute of Public Health, P.O. Box 4404 Nydalen, 0403 Oslo, Norway;(2) Dept. of Plant and Environ. Sciences, Agricultural University of Norway, P.O. Box 5003, 1432 Ås, Norway;(3) Oslo Water and Sewerage Works, P.O. Box 4704 Sofienberg, 0506 Oslo, Norway |