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Regular execution of quality control (QC) tests in medical diagnostic X-ray units is primarily important to provide high-quality images and proper diagnoses with least hazard. The performance criteria in diagnostic radiology in Zanzibar Islands, Tanzania were followed in accordance with the QC guidelines, and the values of the measured parameters were compared with the tolerance limits. The study was designed to perform QC tests on the diagnostic X-ray units in governmental and private hospitals. In this study six QC tests (beam alignment, beam collimation, kV reproducibility, half-value layer (HVL), mAs linearity and kV accuracy) were carried out by using beam alignment tool and Unfors non-invasive X-ray test device (Xi R/F&MAM detector). The measured parameters were conducted in two periods, from 2017 to 2018 (14 X-ray units were considered) and from 2019 to 2020 (16 X-ray units were considered). In both periods, the QC test results indicated that 100% of the X-ray units had acceptable HVL≥ 2.3 mm Al at 80 kVp. In the first period (2017−2018), the QC results showed that 78.57% and 85.71% had acceptable beam alignment (≤3% of the focus to image distance) and beam collimation (≤ ± 2 cm). Of the X-ray units evaluated, 85.71% had tolerable kV reproducibility of 5%, and 71.43% had mAs linearity within the tolerance limit of 10%, whereas 85.71% had acceptable kV accuracy within the tolerance limit of 5%. In the second period (2019−2020), the tolerance limits of X-ray units exceeded by 8.04% for kV reproducibility, 8.04% for kV accuracy, 16.07% for mAs linearity, 8.93% for beam alignment and 8.04% for beam collimation. The exceeded tolerance limits could be attributed to the new X-ray units which have full support of service agreements signed during the second period and increase of the compliances with the Tanzania Atomic Energy Act. No 7 of 2003 and its regulations. Results obtained highlight the need to regularly carry out comprehensive QC tests together with routine equipment maintenance.

This work aimed to assess the levels of heavy metal concentration in ipomoea batatas and spinach associated with uncontrolled municipal waste, motor vehicles fumes, pesticides and fertilizer in the urban west region, in Zanzibar. Twenty samples were randomly collected in local markets and three farms located along a roadside in the urban west region. The samples were analysed using an energy dispersive X-ray fluorescence method at Tanzania Atomic Energy Commission in Arusha. Essential and toxic elements: Mn, Cu, Fe, As, Zn, Pb, and Ni were detected in both ipomoea batatas and spinach. Ipomoea batatas was found to have a higher concentration of Cr, Fe, Cd and Zn while spinach had a higher concentration of Ni, Cr and Zn. The essential elements concentrations of vegetables analysed in the current study were found within safety baseline levels for human consumption. However, the concentration levels of toxic elements were above FAO/WHO permissible limits. The higher concentration levels of toxic elements in ipomoea batatas and spinach might be associated with contamination of municipal waste, chicken manure, motor vehicles fumes or pesticides. Therefore, vegetable cultivation along a roadside in the urban west region in Zanzibar and the use of fertilizer and chicken manure in vegetables introducing high levels of heavy metals in the food chain.