Determination of Radionuclide Activity and Radiological Impact from the Intake of Milk, Wheat Flour, Tea and Coffee

Consumption of food containing radionuclides may contribute to internal dose. Studies on radionuclide content in several types of food should be done to determine effects to human. The objectives of this research are to i) determine the activity concentration in milk powder, tea, flour and coffee samples, ii) to calculate the annual exposure dose in food products and iii) to determine the lifetime cancer risk amongst Malaysians. The concentrations of ²²⁶Ra, ²³⁸U, ²³²Th and ⁴⁰K were determined using gamma ray spectrometry. The study found that the mean activity concentration in milk powder, tea, flour and coffee are 1.6±0.8, 3.3±0.4 , 1.2±0.2, 2.1±0.7 Bq kg^-1 for ²²⁶Ra, 1.6±0.2, 10.7±3.3, 2.1±0.6 and 1.8±0.2 Bq kg^-1 for ²³⁸U, 1.8±0.5, 9.5±2.2, 1.9±0.1, 2.2±0.3 Bq kg^-1 for ²³²Th and 190.2±49.6, 395.4 ±11.9, 57.4±28.5, 429.4±305.5 Bq kg^-1 for ⁴⁰K, respectively. The annual internal exposure dose for children through consumption of milk powder are 63.5 μSv for ²²⁶Ra, 32.2 μSv for ²³²Th, 2.8 μSv for ²³⁸U and 326.5 μSv for the ⁴⁰K, respectively. Whereas, the annual internal exposure dose for adults through consumption of wheat flour, tea and coffee are 13.7 μSv for ²²⁶Ra, 18.0 μSv for ²³²Th, 5.1 μSv year^-1 for ²³⁸U and 24.2 μSv year^-1 for ⁴⁰K, respectively. All radionuclide exposure doses are 425 μSv year^-1 for children and 61.0 μSv year^-1 for adults. This value provides a risk factor of 1. x10^-3 cancer for children and 1.7x10^-4 for adults. It means that the probability of lifetime cancer risk increment of 0.18 % for children (18 people in 10 000) and 0.017 % for adults (1.7 people in 10 000). These values are lower than the ICRP cancer risk factors for the public of 2.5x10^-3 and the total risk from all sources of radiation dose based on the global annual dose of 2.4 mSv year^-1 which is 6x10^-3. The study revealed that the intake of milk powder, flour, tea and coffee do not contribute a significant health hazard and is considered radiological safe to be taken by humans. (author)