Discharges of 131I coming from hospitals and outpatients in the sanitary sewage system of Bogotá

Abstract

An integral sampling methodology was applied to the sewerage network of Bogotá by inspecting wells that carry sanitary water from institutions that use ¹³¹I in nuclear medicine treatments to determine the areas of the city with activity of this radioisotope, which may reach the Salitre wastewater treatment plant and are subsequently discharged into the Bogotá river. The areas evaluated included the location of authorized institutions that use ¹³¹I in nuclear medicine and their patients. A total of 13 wells were sampled in the city, each with three samples, and the characterization of the samples was performed using the technique of high-resolution gamma spectrometry with Ge-HP detector and covered the relevant aspects that must be considered to make a complete characterization of the presence of the isotope studied. Among these factors are the season of the year with precipitation, pipe flow, location of the nuclear medicine facilities, existence of decay systems, number of rooms for treatment with ¹³¹I and water trajectory through the sewage system. Based on the results obtained, it was possible to identify potential sources of radioisotope ¹³¹I that are exceeding the discharge limits established by Colombian regulations (i.e., 19 Bq/L at the discharge point). From the 13 wells sampled, radioisotope ¹³¹I was detected in 11 of them. From the assessed wells, 3 were connected to facilities in which activity was found to be above the discharges limit allowed in Colombia for the sanitary sewer. This research complements the study on traceability of ¹³¹I in Bogotá-Colombia that begins with its importation by radiopharmacies who distribute it to hospital patients and outpatients, continuing its trajectory through management systems or homes to the sewage system of Bogotá, field that had not been studied. It allows inferring the degree of compliance with Colombian regulations and serves as a basis for evaluating regulatory changes in the levels of ¹³¹I dispensing in water networks. Further studies are required to assess the potential impacts of these materials on the local population.

Keywords: (131)I discharge; Gamma spectrometry; Sanitary sewer; Storm sewer.