Cancer risk in houses under study

Press, 24 January 1986, Page 3

Cancer risk in houses under study

PA Wellington The National Radiation Laboratory will start a New Zealand-wide survey of houses this week for high levels of a radioactive. gas that causes lung cancer. The gas, radon, occurs naturally in soil. It is a dense carcinogenic gas and is concerning researchers overseas who have found that it can be a serious indoor pollutant.

Many experts believe radon exposure is the leading cause of lung cancer in non-smokers.

Radon occurs widely. It is produced by the decay of uranium and radium, found in most soils. It can seep from soil and masonry into buildings where it can accumulate at levels about 10 times higher than in the open air.

Radon has a half-life of 3.8 days and decays into various radioactive “daughter” elements. One of these, polonium, when inhaled, delivers a dose of penetrating alpha radiation. This can cause lung cancer.

Energy-efficient houses which restrict air ventilation are known to cause a build-up of radon. Dr Neil Whitehead, formerly with the Institute of Nuclear Science at Gracefield, said tests for radon in one energy-effi-cient house in the Hutt Valley showed a level 70 per cent above those recommended.

It is thought that most New Zealand soils do not contain high radon levels. Its dangers were not realised until high levels were found in homes in Sweden, Canada, Britain, and parts of the United States. According to a recent study reported in the American magazine “Popular Science,” about one million homes in the United States may have radon levels higher than recommended guidelines. In one town in Pennsylvania the living room of a house was found to contain a level 16 times higher than levels permitted in uranium mines. The family had to be evacuated. The owner said: “We were told that breathing the air in our house was the health equivalent of smoking 135 packets of cigarettes a day.”

A recent survey of 2000 British homes had shown some disturbing results, according to the "New Scientist” magazine. The National Radiological Protection Board, the

British radiation watchdog, found that one in 20 homes in Cornwall exposed occupants to more radiation that the maximum dose of 25 millisieverts a year recommended in 1984 by the Royal Commission on Environmental Pollution.

The occupants may face the same risk of contracting lung cancer as they face from all other cancers combined.

“Popular Science” says many experts believe even average levels slightly increase the risk of lung cancer. A pilot study by the National Radiation Laboratory last year on 60 randomly chosen Christchurch houses showed low levels of both radon and gamma radiation. The national survey launched this week hopes to pinpoint areas with naturally high radon levels and houses with construction that concentrates radioactivity. The scientist in charge of the project, Mr Murray Robertson, said that between 500 to 1000 randomly selected houses would be invited to take part in the survey. Participants would be sent a dosemeter card containing plastic strips which would record bombardment by radiation from radon, and a capsule of powder which recorded gamma radiation. Participants would put cards under kitchen tables and bedroom wardrobes for two periods of six months before returning the cards for analysis. Mr Harold Trethowen, of the Building Research Association in Wellington, said a build-up of radon depended to a large degree on the rate of ventilation. Typically, a New Zealand house built in the last 20 years had one complete change of air each hour even when all doors and windows were closed. In Sweden and Canada, where the radon problem was first detected, houses were tightly sealed against severe winters with changes of air only half to a quarter the rate of New Zealand houses.