MN frequencies in the study population subdivided by age (a); significantly higher MN frequencies were found in the older age groups (> 45 years) than in the younger age groups (< 45 years) in the both groups, time exposure year (b); MN values were significantly higher in the ICS group with time exposure of > 10 years in comparison to < 10 years (p = 0.039) and exposure status (c); significant difference in MN frequency was also observed between occupational radiation doses of ≥ 3 mSv and < 3 mSv during last year of exposure (p = 0.002).