Chromosome aberration test limitations

In one epidemiological study testing benzene s effects on chromosomal aberrations, benzene appeared to exert a nonrandom effect on chromosomes one, two, four, and nine (Sasiadek et al. 1989). However, this study is limited because relatively few controls were used and all participants (control and exposed) were smokers. The effects of smoking may have confounded the results. In a later paper, extra break points were confirmed on chromosomes 2 and 4, only (Sasiadek and Jagielski 1990). Sister chromatid exchange was not found to be a significant effect of benzene exposure in humans (Seiji et al. 1990 Yardley-Jones et al. 1988) however, poor control selection was used in both studies. Refer to Table 2-5 for a further summary of these results. 

The studies reported on scopolamine are also limited and Inconclusive, even though the capacity to Induce ONA damage and point mutations In bacteria and chromosomal aberrations In mammalian cells has been tested. 

Thus, SCE tests have been largely discontinued by industry and are recommended by regulatory agencies on a limited basis. However, this assay continues to be used as a research tool and in some regulatory settings. For example, despite its poor concordance, the SCE assay continues to be used by the NTP, in part because SCE techniques are sufficiently similar to those used for in vitro chromosomal aberration assays so that the two tests can efficiently be used in parallel by cytogenetic testing laboratories. 

IV. Concerns over growing numbers of nonrelevant positive findings in mammalian cell tests in vitro will also be counterbalanced by limiting the levels of cytotoxicity to at most 50% for in vitro chromosome aberration and micronucleus tests. This proposal is supported by an extensive review of results obtained with in vitro hazard identification testing and in vivo risk assessment testing in the pharmacentical industry. 

Ames test, chromosomes aberration, cytogenetic test negative Occupational exposure limit 6mg/m. ... 

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