An anti-smoking activist and community-health specialist has urged the government to ban smoking in cars and even homes to protect children's health.
Professor Lam Tai-hing was speaking after a new study, published yesterday, showed that second-hand smoke can make children prone to heart attacks and strokes later in life, in addition to other known risks such as lung cancer, middle-ear disease and respiratory disease.
Lam, professor of community medicine at the University of Hong Kong, said that while smoking in cars when children were present had been banned in some countries, so far no authorities had made a similar ruling for private households.
"Smoking in front of children should be seen as poisoning and abusing them," he said. "There are laws that protect children against being abused, why is it we don't consider second-hand smoking as a kind of abuse?"
Lam said Hong Kong so far had no legislation specifically to protect children from second-hand smoke.
The study, published in the European Heart Journal yesterday, said data from 2,401 people in Finland and 1,375 in Australia showed passive smoking led to a thickening of children's artery walls, ageing blood vessels by 3.3 years by adulthood.
Scientists used ultrasound to measure the thickness of the children's artery walls once they had reached adulthood.
The results showed that in adulthood, the carotid IMT - a measure of the innermost two layers of the arterial wall - was 0.015 millimetres thicker when both parents smoked than when neither did.
Researcher Seana Gall, who led the study at the University of Tasmania, said this was an irreversible risk of heart attacks or strokes later in life.
The researchers said the findings showed that reducing children's exposure to smoke was a public health priority.
"Legislation can reduce passive smoke exposure," they wrote, adding that banning smoking in cars with children in them would have a significant positive effect.
Smoking in cars carrying children is already banned in the United States, Australia and Canada. Britain is set to follow soon.
According to the World Health Organisation, 6 million people a year die due to smoking, while 600,000 die from exposure to other people's smoke.