Experimental Assessment of Workplace Radiation Exposure in Diagnostic X-ray Medical Imaging Centres in Benin from 2019 to 2020.

The ease of prescribing radiological examinations has prompted an expansion in radiological procedures and, consequently, an increase of occupational dose to medical imaging workers. However, little is known about radiation exposure in the workplace of medical radiology professionals in many countries, and in Benin particularly. The purpose of this study was to assess ambient radiation doses in diagnostic X-ray medical facilities in Benin and to observe whether exposure levels are below reference levels. A total of 72 public and private medical imaging centres participated in a cross-sectional study carried out from June 2019 to February 2020 in Benin. These centres had 59 X-ray, four chest and six computed tomography (CT) scan rooms. A calibrated radiameter able to measure short, pulsed or continuous X fields and gamma/beta (50 nSv to 10 Sv) was used to measure exposure levels in these functional rooms. Scattered X-ray doses and exposure time from radiological examinations both behind the lead glass of the control area to assess the levels of exposure of professionals and outside of the examination room to evaluate the level of exposure of the public (including non-exposed workers) have been provided. Equivalent doses estimated per hour were compared with the reference levels of 7.50 and 0.05 µSv per hour for workers and the public, respectively. At the control area, the mean/median (min-max) equivalent doses were 0.09/0.07 (0.00-0.21), 2.39/0.13 (0.00-75.67), and 228.39/28.65 (0.39-869.75) µSv per hour for the chest, X-ray, and CT-scan rooms, respectively. Among 69 examination rooms, 13.04% of the equivalent dose estimated in the workplace behind the lead glass was greater than 7.50 µSv per hour; 65 out of 69 examination rooms showed that 40.00% of the equivalent dose estimated behind the doors was greater than 0.05 µSv per hour. These results demonstrated that current controls, including leaded glass separating the control panel and leaded doors between the examination room and the corridor, are inadequate to limit radiation exposures. The controls must be upgraded and a dosimetry program should be implemented to monitor exposures of employees, patients, and visitors.

Determinants of AhR-mediated transcriptional activity induced by plasma extracts from Nunavik Inuit adults.

The exposure of Inuit people to polychlorinated biphenyls (PCBs) and chlorinated pesticides has been well characterised but little is known regarding their exposure to dioxin-like compounds, which induce toxic effects through binding to the aryl hydrocarbon receptor (AhR). In order to obtain a global measure of persistent organic pollutants in plasma that interact with this signalling pathway, we used a luciferase reporter gene assay to assess the AhR-mediated transcriptional activity elicited by plasma sample extracts from 874 Inuit adults who were recruited in the course of a prospective epidemiological study conducted in Nunavik (Québec, Canada). Several sociodemographic, anthropometric, dietary and lifestyle variables were considered as possible modulating factors of the AhR-mediated activity in multivariate statistical analyses. The geometric mean AhR-mediated activity expressed as 2,3,7,8-tetachlorodibenzo-p-dioxin equivalents was 8.9 pg g(-1) lipids (range: <5-144 pg g(-1) lipids). PCB-153 concentration measured by high-resolution gas chromatography-mass spectrometry was moderately correlated to AhR-mediated activity (Pearson's r=0.53, p<0.001). Multiple linear regression analyses revealed that age and omega-3 fatty acids in erythrocyte membranes (an index of marine food consumption) were positively associated with plasma AhR-mediated activity (p<0.001), whereas a negative association was noted with body fat mass (p=0.037). These results suggest that AhR-mediated transcriptional activity of Inuit plasma extracts is linked to their organochlorine body burden, most likely that of dioxin-like PCBs, polychlorinated dibenzo-p-dioxins and polychlorodibenzofurans. AhR-mediated transcriptional activity measures may prove useful in investigating possible associations between exposure to AhR agonists and adverse health effects in this indigenous population.