Replies to LegCo questions

LC Q18: Radiation levels of vegetables

Following is a question by the Hon Lau Kong-wah and a written reply by the Secretary for Health, Welfare and Food, Dr Yeoh Eng-kiong, in the Legislative Council today (October 23):

Question:

It has been reported that laboratory tests on the radiation levels of samples of local and imported vegetables are regularly conducted by the Hong Kong Observatory, and the latest test results show that there are indications of an increase in such radiation levels in recent years. In this connection, will the Government inform this Council:

(a) whether, in respect of the increase in the radiation levels of vegetables, it has made inquiries with vegetable farmers or conducted site inspections; if so, of the details;

(b) whether it has studied the factors contributing to the increase in the radiation levels of vegetables; if so, of the results; and

(c) whether it has studied the possible measures to reduce the radiation levels of vegetables, such as enhancing the education on farming practices for farmers?

Reply:

The Hong Kong Observatory recorded changes above detectable level only in potassium-40 from vegetable samples. These variations in the levels of potassium-40 in samples of vegetables are within the range of normal background fluctuations due to the normal fluctuations of potassium concentration in food produce.

Potassium-40 is not an indicator radionuclide for the monitoring of the level of radioactivity in food. It is a naturally occurring isotope of potassium. The purpose of measuring potassium-40 is to ensure the consistency of the Hong Kong Observatory's environmental monitoring programme and the reliability of the measurements of other radionuclides.

The proportion of potassium-40 in potassium is constant and not related to any man-made activities. Both plants and human bodies are capable of maintaining a homeostatic balance of the amount of potassium and hence the proportion of potassium-40 therein. According to the Report of the General Assembly of the United Nations Scientific Committee on the Effect of Atomic Radiation (2000), the radiation dose from potassium-40 to human is stable and independent of food diets.

For the radioactivity level in food produces, the Food and Environmental Hygiene Department has been monitoring the levels of caesium-134, caesium-137 and iodine-131 which are internationally commonly employed indicators to measure man-made radioactivity in food including vegetables. The radiation testing results of food, including vegetables, have all along remained below the prescribed safety limit in the standard set out by Codex Alimentarius Commission.

Since potassium-40 is a naturally occurring isotope not amenable to interventions, investigative actions such as site inspections or inquiries with farmers are neither necessary nor helpful in explaining the recently observed phenomenon. Furthermore, it is not possible to take any action to reduce or increase the level of potassium-40 naturally present in the environment.

END/Wednesday, October 23, 2002
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