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A GOVERNMENT report has pinpointed 19 sites in Hong Kong where radioactive radon gas has reached levels almost four times those recommended as safe by the World Health Organisation.

  The Sunday Morning Post has obtained a copy of the study's findings, which list locations and radon levels recorded by government scientists . . . but which have been kept secret from the residents concerned.

  People living in radon-heavy areas - including the New Territories village of Pat Heung and the heavily-populated urban areas of Yau Ma Tei and North Point - said officials had told them their buildings registered over 200 in gas tests, but were unaware those figures were double or triple WHO guidelines.

 The WHO and the International Commission of Radiological Protection warn that 200 bequerels per cubic metre (bq/m3) is the maximum level acceptable before radon inflicts health damage.

  In areas exceeding these levels - where residents are at a significantly higher risk of contracting lung cancer - they recommend immediate remedial action.

  But last week, Hong Kong's principal environmental protection officer, Raymond Leung Pak-min, maintained that occupants of buildings with high radon levels had nothing to fear.

  Building owners had been told to open windows to improve air circulation and follow-up tests showed all the high-radon buildings had returned to safe levels, he said.

  But a radiation expert at the University of Hong Kong said the government guidelines were no guarantee of safety.

  Dr John Leung Kon-chong, a lecturer in the university's radioisotope unit, said: 'After the windows are closed, levels rise rapidly. In general, it takes one or two days to reach half the maximum [original] concentration.'   For tenants in high-emission buildings, leaving windows open during the day is insufficient. When night falls and windows are shut, the radioactive gas will build up to dangerous levels.

  Radon is odourless and invisible, and is produced by decaying radium found in granite, the rock on which more than a third of the territory is founded.

  The rock is also quarried for building materials, surrounding Hong Kong residents with walls which emit radon gas. Hong Kong's concrete contains more radon-releasing radium than any other country in the world, according to a University of Hong Kong study.

  Radon forms when radium in the granite disintegrates, and as the radon gas disintegrates, radioactive particles are formed. When either the gas or particles are breathed into the lungs, they stick to the tissue and emit radiation within the lungs, increasing the risk of cancer.

  In Britain, authorities are running costly campaigns to identify houses with the highest radon levels and change the foundations and floors to keep the gas out. Residents can claim grants up to $12,000 to fix their homes, and new houses in danger zones are built to radon-proof standards.

  But Mr Raymond Leung dismissed such measures for Hong Kong's hotspots.

  'We're not too concerned about [the 19 zones]' he said. 'We told [the residents] a list of measures to take. If they follow the advice, it should bring it down to an acceptable level.'   The Pat Heung reading, at 745 almost four times the WHO danger limit, had probably been taken in a stone hut and 'not many people live in stone huts', Mr Leung said.

  Some detectors had also been placed in poorly ventilated rooms, producing higher results, he said.

  The survey put Hong Kong's average radon concentration at 98 bq/m3. But even this level could account for about 13 per cent of the territory's lung cancer deaths, according to EPD figures.

  International studies have linked radon emissions to lung cancer. British researchers found people exposed to a 'normal' 20 bq/m3 had a lifetime lung cancer risk of one-in-300. But those exposed to radon levels of 200 bq/m3 ran a one-in-30 risk of cancer.

  The United States Environmental Protection Agency and UK National Radiological Protection Board estimate indoor radon is responsible for about 14,000 lung cancer deaths a year in the US and 2,000 in Britain - making radon the main cause of lung cancer after smoking. Children between five and 14 are most at risk. Cigarette smokers are also more vulnerable.

  Smokers were estimated to be three times more likely than non-smokers to develop lung cancer when exposed to high radon levels.

  Links between radon and cancer made headlines in Hong Kong in 1990 when two brothers developed a cancer similar to leukaemia, which affected their lymph glands - against odds of one to 1.6 billion.

  The brothers' doctor pointed to radon levels, and a leading cancer specialist said a statistical relationship between radon gas and leukaemia had been shown.

  In 1988, City Polytechnic - now City University - recommended the Government set standards for building materials, but there are still no regulations to monitor the levels of radon in building materials.

  Government spokesmen have pledged to release radon warning letters, but are still working on the material.

  'The only solution is to use those building materials with less radium content,' University of Science and Technology physicist Dr Paul Chan Muk-wah. 'Homes should be designed with better ventilation.' 



Radon gas four times safe levels