Practical evaluation of mutagenicity data in mammals for estimating human risk.

Chrosomal aberrations are known to constitute a significant portion of the genetic risk from practically all mutagenic agents. These effects are diverse in both nature and in the stage of the germ cells' life cycle at which they are produced. Arguments are made pointing out many of the problem areas in our understanding the significance of chromosomal aberrations in relation to genetic risk. Data are summarized that offer explanations as to (1) why so few chromosomal effects are recovered after treating spermatogonial stem cells, (2) how chromosome damage and dominant lethality are correlated when postmeiotic germ-cell stages are treated with MMS, and (3) why so few reciprocal translocations are recovered after irradiation of oocytes.