BIOMONITORING OF POSSIBLE HUMAN EXPOSURE TO ENVIRONMENTAL GENOTOXIC CHEMICALS - LESSONS FROM A STUDY FOLLOWING THE WRECK OF THE OIL TANKER BRAER

In January 1993 the oil tanker Braer ran aground in the Shetland islan ds, Scotland. Approximately 80,000 ions of crude oil were released. Ex ceptionally high winds caused extensive pollution and exposure of the local population to crude oil. We describe the study which was immedia tely set in place to examine the exposed population for evidence of ge notoxic exposure. Brood samples were token and primary DNA damage was measured in the mononuclear cell fraction by the butanol modification of the P-32-postlabelling method. Mutation was measured at the hprt lo cus in T lymphocytes. No evidence of genotoxicity was obtained for eit her end point, but nevertheless, we believe that useful lessons were l earnt, which should be incorporated into the design of future studies: (1) A rapid response is essential, and even if sufficient funds are n ot immediately available, it is still worth attempting to obtain sampl es quickly and use cryopreservation, also to attempt to estimate expos ure. (2) Adequate numbers of volunteers must be sought, together with enough controls, not just to allow meaningful analysis but to overcome toss of samples and failure of things to go according to plan. (3) Po ints concerning laboratory practice include: (i) samples should be cod ed, (ii) clearly defined and proven protocols should be used, (iii) ir replaceable samples should not be used for method development, (iv) sh ould a problem become apparent during the study, work on such samples should cease immediately until the problem is solved, (v) all critical experimental components should be pretested against a laboratory stan dard. (4) The study design should include replicate experiments to mon itor experimental variability and reproducibility, as well os internal standards and cryopreserved ''in house'' samples. Care must be token that samples from any one exposure group are spread between a number o f independent experiments and that each experiment includes samples fr om a number of exposure groups. (5) A computerised data base should be maintained with full details of experimental variables, donor attribu tes, and raw data so that any contribution of experimental artefacts t o ''outlier'' results can be monitored. (6) Because of the nature of t he statistical variation for many environmental genotoxicity end point s, only a large-scale study is likely to be capable of yielding useful information. (C) 1997 Wiley-Liss, Inc.