131I discharges to the marine environment and uptake by algae in Sydney, Australia

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South Pacific Radioactivity Association
The use of radiopharmaceuticals in nuclear medicine results in radioactive material being discharged to the sewer as human waste. Treated sewage effluent is in turn discharged to the marine environment through coastal and deepwater outfalls. 131l is the dominant medical isotope discharged to the environment as treatment doses can be large (up to 8 GBq) and excretion from patients is rapid. Also, 131l has a half life (8.04 days), which is significantly greater than the effluent residence time in the sewerage system (< 1 day), and a low Kd resulting in a low removal during treatment. 131l levels from <1 to 150 Bq/L have been measured in effluent from Sydney sewage treatment plants. Following discharge of effluent to ocean outfalls, 131l levels in the seawater are likely to be low as a result of dispersion and dilution of the effluent. However, 131I is easily detected in macroalgae growing near coastal outfalls as the algae bio-accumulate iodine. In fact, 131I levels between 1 and 375 Bq/kg have been observed in various macroalgae species near the outfall from Cronulla sewage treatment plant in Sydney, since November 1995. This paper presents data on 131l levels in effluent and uptake by algae growing near shoreline outfalls in the Sydney region. Radiation doses to marine biota from 131l discharged to coastal waters are calculated to be very small and below the ERICA screening level of l0 uGy/hr. Human dose assessment is also discussed.
Radiopharmaceuticals, Nuclear medicine, Sewage, Seas, Coastal regions, Algae, Iodine 131, Liquid wastes
Veliscek Carolan, J, Hughes, C. E., Hoffmann, E. L., & Loosz, T. (2008). 131I discharges to the marine environment and uptake by algae in Sydney, Australia. Paper presented to SPERA 08, South Pacific Environmental Radioactivity Association Conference, University of Canterbury, Christchurch, New Zealand, 23-27 November 2008. (pp. 40).