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The Hong Kong Observatory detected very minute amount of artificial radionuclide Iodine-131 from air samples collected at King's Park from noon, March 26 to noon, March 27 and from noon, March 27 to noon, March 28. The concentrations of Iodine-131 measured from these two samples were 0.0000625 Bq/m3 and 0.0001869 Bq/m3 respectively, which were respectively 1/10,000,000 and 1/3,500,000 the concentration level required for taking protective actions.
Since the earthquake and tsunami event in Japan on March 11, the Observatory has strengthened the monitoring of concentration of radioactive substances in the air. The frequency of sample collection from the air sampler at King's Park has increased from once weekly to once daily so as to operate round-the-clock for radioactivity measurement. Owing to the very low radiation dose, the Observatory needs to extend the measurement time from normally a few hours to 22 hours to meet the reliability requirement. Even with this measuring method, the amount of radioactive iodine detected is still very minute that will not affect public health and no precautionary measures are required. Radiation level in Hong Kong remains normal and the public needs not worry. The Observatory will continue to monitor closely and routinely announce the measurement results.
Note: The concentration level required for taking protective actions is called "Derived intervention level" (DIL). The DIL for inhalation of Iodine-131 from the air is 661.38 Bq/m3.
Ends/Tuesday, March 29, 2011
Issued at HKT 21:36
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