Dose assessment for marine biota and humans from discharge of 131I to the marine environment and uptake by algae in Sydney, Australia.

Abstract

Iodine-131 reaches the marine environment through its excretion to the sewer by nuclear medicine patients followed by discharge through coastal and deepwater outfalls. (131)I has been detected in macroalgae, which bio-accumulate iodine, growing near the coastal outfall of Cronulla sewage treatment plant (STP) since 1995. During this study, (131)I levels in liquid effluent and sludge from three Sydney STPs as well as in macroalgae (Ulva sp. and Ecklonia radiata) growing near their shoreline outfalls were measured. Concentration factors of 176 for Ulva sp. and 526 for E. radiata were derived. Radiation dose rates to marine biota from (131)I discharged to coastal waters calculated using the ERICA dose assessment tool were below the ERICA screening level of 10muGy/hr. Radiation dose rates to humans from immersion in seawater or consumption of Ulva sp. containing (131)I were three and two orders of magnitude below the IAEA screening level of 10muSv/year, respectively.