World Aquaculture Singapore 2022

November 29 - December 2, 2022



Lak Kuen Mak*, Jasmine Toh, Lay Peng Neo, Shoo Peng Koh, Yuansheng Wu,

Sheot Harn Chan


National Centre for Food Science

Singapore Food Agency

10 Perahu Road, Singapore 718837


Currently, international food safety standards for radionuclides are established based on the context of responding to a nuclear and national emergency. However, the robust dietary exposure assessment for radionuclides should consider contributions from both post-nuclear incidents and existing background levels. There has been ongoing IAEA and FAO discussion on the need for data gathering of radionuclides levels in food commodity and drinking water during non-emergency situations, which covers both naturally occurring and human-made radionuclides. This survey aims to study the normal background levels of gamma-emitting radionuclides in fishes farmed in Singapore. The levels of 10 gamma-emitting radionuclides comprising of naturogenic (40K, 212Bi, 212Pb, 214Bi, 214Pb, 226Ra and 228Ac) and antropogenic radionuclides (131I, 134Cs, 137Cs) were analysed in 42 fishes collected from farms located in the East and West Johor Straits, Southern coastal and freshwater fish farms in Singapore. Fish species analysed include milkfish (9), snapper (9), grouper (7), seabass (6), tilapia (4), jade perch (2), catfish (2), pompano (1), mullet (1), and snakehead (1). The measurements were performed using high-purity germanium detector gamma spectrometer (HPGe). Amongst all the gamma-emitting radionuclides monitored, naturally occurring Potassium-40 (40K), a long-lived radioisotope with half-life of 1.251x109 years is present in all sample. Potassium-40 has a natural abundance of 0.012%, coexisting with stable isotopes 39K and 41K, with a combined natural abundance of 99.988%, is part of the common minerals present in all food of animal and plant origins. The level of 40K in fish ranged from 40.3 to 140 Bq kg-1. None of the samples is detected with the three anthropogenic radionuclides. The annual effective dose of the gamma-emitting radionuclides analysed in this study was estimated to be about 0.01 mSv per person when considering the dietary intake of fish for an average local consumer. Based on the calculated dose, about 98.5% is contributed by the natural radionuclide, 40K. Hence, the exposure to radionuclides from consumption of fish is significantly lower than the worldwide average annual effective dose of 0.29 mSv via ingestion of food and water by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR 2008).