Spontaneous and induced micronuclei and UDS in peripheral lymphocytes

We have examined the distributions both of spontaneous and X-ray-induced micronuclei (MN) and of spontaneous and UV-induced unscheduled DNA synthesis (autoradiographic grains; UDS) in cultures of peripheral blood lymphocytes from normal, healthy human volunteers. While the spontaneous MN and UDS do not differ significantly from the expected Poisson distributions, both the induced MN and UDS are strongly overdistributed (i.e., variance much greater than mean). This not only must be allowed for in statistical tests used for population monitoring, but offers suggestive evidence that there are large differences in radiation response from sample to sample, some of which may reflect true differences among normal, healthy subjects.