Population doubling: a simple and more accurate estimation of cell growth suppression in the in vitro assay for chromosomal aberrations that reduces irrelevant positive results.

International guidelines for cytotoxicity limits for the in vitro chromosomal aberration assay require reductions in cell growth of greater than 50%. This sets no upper limit on toxicity and there is concern about the number of false or irrelevant results obtained in the aberration assay, i.e.