Covering up asbestos in earthquake-damaged homes is "completely immoral", a Christchurch man exposed to the material says.

Ernie Patterson, 75, was "completely shocked" when he found out recently that he has two small asbestos lesions on his lung, and he is urging New Zealand authorities to "use common sense" to avoid asbestos-related diseases and deaths.

The Earthquake Commission (EQC) estimates 43,000 Christchurch homes due for quake repairs could contain asbestos.

In about 10 per cent of cases, undamaged asbestos in ceilings has been encased behind plasterboard instead of being removed.

Homeowners will be told if that is done in their house, but there are concerns encasement may encourage them to hide the information when they sell their property.

Patterson, a retired electrical engineer, thinks he was exposed to asbestos in Christchurch about 25 years ago.

"I had two contracts with a company . . . where I supervised the insulation of a boiler and chilled water piping," he said.

"I was never in contact with asbestos. I was merely in the area, and for a very short time, too."

The lesions on Patterson's lung could cause mesothelioma, an asbestos-related cancer.

The encasement practice made no sense, he said.

"Covering up asbestos is just ridiculous. . . . It's dangerous, and down the track people won't be aware that there is asbestos in their home. It has to be the authorities' responsibility, and all asbestos should be removed.

"They're burying their head in the sand because by the time this causes serious problems, they will be long gone."

Canterbury District Health Board medical officer of health Alistair Humphrey last week told The Press that asbestos was harmful only if a person was exposed to high levels of the material over a long period.

He said harm from a short exposure "can happen".

He said the encasement policy was a "landmine" for potential health problems.

EQC general manager of customer services Bruce Emson yesterday said homeowners might have to pay if they wanted asbestos not damaged or deteriorating removed from their property.

"This would be decided on a case-by-case basis. Our job is to repair earthquake damage, not to make improvements or betterment to the property," he said.

The Ministry of Business, Innovation and Employment did not respond to The Press for comment.

- © Fairfax NZ News