Assessment of radionuclide contents in food in Hong Kong.

Baseline values of concentrations of the natural radionuclides (238U, 226Ra, 228Ra/232Th, 210Pb) and artificial radionuclides (137Cs, 60Co) in food and drinks (tap water, milk, and water-based drinks) were determined by gamma spectroscopy. All food and drinks were found to contain detectable 40K contents: 0.1 to 160 Bq kg(-1) (fresh mass) for food and 0.006 to 61 Bq L(-1) for drinks. Most of the other natural radionuclides in solid food were found to have contents below the minimum detectable activities (MDA). More samples in the leafy vegetable, tomato, carrot and potato categories contained detectable amounts of 228Ra than the meat, cereal, and fish categories, with concentrations up to 1.2 Bq kg(-1) for the former categories and 0.35 Bq kg(-1) for the latter categories. The 238U and 226Ra radionuclides were detectable in most of the water-based drink samples (reaching 0.22 and 0.015 Bq kg(-1), respectively), and the 228Ra and 210Pb radionuclides were detectable in fewer water-based drink samples. The 137Cs contents in solid food were detectable in most of the solid food samples (reaching 0.59 Bq kg(-1)), but in drinks the 137Cs contents were very low (the maximum value is 0.23 Bq L(-1)) and normally lower than the MDA values. Nearly all the 60Co contents in food and drinks were below the MDA values and their contents were below those of 137Cs. The results indicate that drinks provide higher intake of natural radionuclides than solid food, but the solid food provides higher intake of 137Cs than drinks. From the measured concentrations, estimates were made on the consumption rate of radionuclides from food and drinks. The health effects due to the ingestion of the radionuclides were evaluated by calculating the committed effective dose. The committed effective dose due to the ingestion of natural radionuclides was estimated to be 69 microSv and 280 microSv for an adult male and female, respectively. The committed effective dose due to the ingestion of 137Cs and 60Co was estimated to be 0.5 microSv for both an adult male and female. The contributions from these two artificial radionuclides were less than those from the natural radionuclides by a factor of more than 100 and were also below the 1 mSv limit set in the new ICRP recommendations.