[1] UNIV YORK,DEPT BIOL,JACK BIRCH UNIT ENVIRONM CARCINOGENESIS,YORK YO1 5DD,N YORKSHIRE,ENGLAND
[2] LAWRENCE LIVERMORE NATL LAB,BIOL & BIOTECHNOL RES PROGRAM,LIVERMORE,CA
[3] LAWRENCE LIVERMORE NATL LAB,CTR ACCELERATOR MASS SPECTROMETRY,LIVERMORE,CA