Purpose: The present study was an attempt to determine the spontaneous frequency of micronuclei (MN) in newborns from High Level Natural Radiation Areas (HLNRA) and the adjoining Normal Level Radiation Areas (NLNRA) of the monazitebearing Kerala Coast in Southern West India using Cytochalasin Blocked Micronuclei (CBMN) assay.

Materials and methods: Human umbilical cord blood samples were collected from a total number of 271 newborns (61 from NLNRA and 210 from HLNRA), born to mothers aged between 17 and 37 years (mean maternal age: 24.08±4.23 years). Lymphocyte cultures were set up following microculture techniques and cultures were terminated at 72 hours. Cytochalasin B at a concentration of 4.0 µg/ml was added to the lymphocyte cultures at 44 h. Enumeration of micronuclei was restricted to Cytochalasin Blocked binucleated (BN) cells only.

Results: The frequency of MN among the newborns from NLNRA (1.40±0.12) per 1000 BN cells was not statistically  significant as compared to HLNRA newborns (1.33±0.04) per 1000 BN cells. Our data did not show any radiation dose response. Odds ratios (OR) and confidence intervals (CI) have been calculated to see statistical significance in the mean MN frequency among the newborns from various dose groups with respect to control and it did not reveal any significant difference (p> 40.05). A marginal increase in the frequency of micronuclei was observed among the female newborns as compared to males with increasing mothers’ age groups except for the mothers aged >30 years, though not statistically significant.

Conclusion: The baseline frequency of micronuclei in HLNRA newborns is not statistically different from NLNRA newborns suggesting that elevated level of naturally occurring radiation has no significant effect on the induction of micronuclei frequency among the newborns.