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Micronuclei as a marker for medical screening of subjects continuously occupationally exposed to low doses of ionizing radiation

We have read the article by Pajic et al. entitled “Micronuclei As A Marker For Medical Screening of Subjects Continuously Occupationally Exposed to Low Doses Of Ionizing Radiation” that is accepted to publish in the journal of Biomarkers, DOI: 10.1080/1354750X.2016.1217934 (Pajic et al. 2016). Pajic et al. evaluated micronuclei as a screening marker of occupational ionizing radiation exposure. The authors showed that the mean frequencies of micronucleus test parameters were significantly higher in exposed persons and they revealed increase of micronucleus yield with duration of exposure by 0.303MN/year. Although the paper published by Pajic et al. is well-structured and can be considered as a significant contribution in this field, it has a minor shortcoming. While Pajic et al. report that they have paid attention to confounding factors such as the use of medicinal products and contraception, they did not provide any information about the annual effective dose of the radiation workers. They only stated that “Almost all radiation workers in Serbia use passive dosimeters for monthly and yearly radiation monitoring. This kind of personal physical dosimetry showed that the mean accumulated absorbed dose for the hospital workers was below the permissible limit of the ICRP (ICRP 2007)”. As all of radiation workers, regardless of the great diversity in their annual effective doses, are expected to receive annual doses much below the dose limits suggested by ICRP, it can be claimed that almost nothing is known about the key factor of the annual doses in the study conducted by Pajic et al. It is worth noting that in the studies on the frequency of micronuclei in different groups of radiation workers, other researchers have clearly reported the mean exposure of the individuals participated in their studies (14 different studies are summarized in a paper published by Ropoloa in 2012 (Ropolo et al. 2012)). We have also previously addressed the shortcomings of the studies that ignored the great variation of annual effective doses of radiation workers who are involved in different procedures (e.g. being involved in fluoroscopic procedures) (Mortazavi 2015, Mortazavi and Jooyan 2015). When the magnitude of the occupational exposures are unknown, tracking the role of radiation in any biological effect will be hard or even impossible (Mortazavi 2015). A study conducted in the Netherlands on 144 X-ray workers showed that the effective dose for 131 of the 144 radiological workers was lower than it would have been if they had stayed at home “In 2008 only 13 of the 144 radiological workers received a dose higher than their not-working equals”. All 13 radiological workers who received higher doses were involved in interventions or fluoroscopic studies (Kemerink et al. 2011). Therefore, the findings of Pajic et al. could be to some extent affected by the key factor of the lack of data about the annual effective doses received by different radiation workers. Furthermore, regarding the exposed worker population, there is no mention of the precise type of work leading to the exposure. As various procedures lead to highly variable exposures to the workers, lack of this information is a flaw of this paper. Moreover, regarding the exposure duration, it is not clear why Pajic et al. have divided the population into two groups, i.e. 5–15 years and 16–30 years of occupational exposure (while in testing the age, the population was divided in 10 years intervals). In this light, it would have been of interest to present a dot plot showing the correlation between the number of MN per 1000 BN vs. the number of years of occupational exposure, together with a linear regression.