Chromosome aberrations and micronuclei in lymphocytes of medical radiation workers exposed to ionizing radiation below dose limit

ABSTRACT

Ionizing radiation induces various kinds of DNA damage in which may lead to chromosomal aberrations [CA]. Inspite of growing importance in the risk assessment, the dose yield kinetics of CA and their implications for dose assessment are not well established in exposures to low level radiation. In the present study, cytochalasin-B blocked micronucleus assay and metaphase analysis were used as test systems to monitor hospital radiation workers who received chronic low dose ionizing radiation below dose limit. Heparinized blood samples were taken from healthy non-smoker radiology and radiotherapy workers occupationally exposed to X and gamma rays and healthy population whose duties do not expose them to radiation sources and chemical agents. The whole body dose was measured by film badge. Lymphocytes were cultured in RPMI-1640 supplemented with 15 percent FBS, and metaphase spread was prepared using standard cytogenetic method. Cytochalasine-B [3 micro g/ml] treatment was used for binuclei micronuclei assay. 100 mitoses and 1000 binuclei lymphocytes were scored for CA and micronuclei [MN] respectively. Results show a high frequency of CA mainly deletions and simple breaks in radiation workers compared to control [p<0.001].Also results show the mean MN/cell was significantly [p<0.001] higher in radiation workers [0.035] when compared to non exposed individuals [0.022]. A relatively high frequency of MN and CA formation in lymphocytes of radiation workers compared to non exposed individuals might be due to an accumulation of initial DNA damage in people exposed to chronic doses of radiation leading to detectable genetic damages. These observations might imply that the current occupational exposure levels might be inadequate to prevent an increase in chromosome damage rate