Second-hand smoke more toxic than inhaled fumes

A person who spends time near a public smoking zone can face health risks similar to those faced by someone in an enclosed area with a smoker, despite the public area being well-ventilated.
PHOTO: Second-hand smoke more toxic than inhaled fumes

SINGAPORE - Puffing away at home or in other enclosed areas, or even at an outdoor smoking zone, can seriously affect people who linger nearby.

They have a long-term risk of getting cancer, according to a recent study by National University of Singapore (NUS). The study, published in February's edition of the Science Of The Total Environment journal, found that second-hand smoke, or sidestream smoke, is more toxic than the fumes inhaled by the smoker himself.

It contains higher concentrations of harmful metals such as lead and cadmium. Such toxic elements, being soluble in water, can dissolve upon contact with moist tissues in the lungs or airways and, eventually, end up in the person's bloodstream.

Dr Teoh Oon Hoe, who heads the respiratory medicine service at KK Women's and Children's Hospital's department of paediatrics, said damage from inhaling tobacco smoke is immediate and cumulative.

Tobacco smoke contains more than 7,000 chemicals, of which hundreds are toxic and can irritate the tissue lining of the air passages in the lungs.

They can even destroy cilia, which are microscopic hair-like projections which sweep away mucus and dust in the air passages, said Dr Teoh, who was not involved in the study.

Carcinogenic chemicals also damage DNA in cells, which may lead to cancer, such as that of the lungs.

Smouldering cycle

Some 1,200 new cases of lung cancer are reported every year, according to figures from the Singapore Cancer Registry. It is the most deadly cancer for men here, and the second-most for women, causing about 1,100 deaths a year.

Associate Professor Rajasekhar Balasubramanian, who led the NUS study, said second-hand smoke is emitted during the smouldering cycle of the cigarette, which occurs over a longer duration of time.

The smoker, for instance, is estimated to puff on the cigarette for just two seconds every minute.

This means that second-hand smoke is produced for the remaining 58 seconds of every minute.

That is why higher levels of harmful substances were found to be exposed to passive smokers, said the deputy head of special projects and the programme director for environmental engineering at NUS.

The experiments were conducted using a cigarette smoke machine in an airtight chamber. This machine simulates the action of smoking.

Each cigarette was "smoked" for up to nine minutes, with puffs lasting two seconds per minute. Four brands of cigarettes were used. Both the "inhaled" and second-hand smoke were trapped in filters and then analysed for harmful elements.

The NUS researchers also went further to test three scenarios in which a passive smoker may find himself in. They are:

In the presence of one smoker in a small room with limited ventilation; In the presence of one smoker, but in a bigger room with a higher level of fresh outdoor air; and Standing near five smokers in a well-ventilated outdoor environment, such as a public smoking zone.

Results show that smokers who puff in enclosed areas with limited ventilation, such as at home, would inflict the most harm on others.

"Apartments and homes, being enclosed, have less ventilation and, therefore, less dispersion of polluted indoor air compared to outdoor environments," said Prof Bala.

"Moreover, indoor air tends to migrate from one room to another, for example, through air-conditioning ducts or open doors," he added.

The most surprising finding, he said, was that a person staying near a smoking zone - as depicted in the third scenario - can also face similar health risks in the long run, despite such areas being well-ventilated.

Other studies have shown that second-hand smoke increases the risk of lower respiratory illnesses, such as pneumonia and poor asthma control among children, pointed out Dr Teoh. "There is no safe level of exposure to tobacco smoke - both as a smoker or as a person who is passively inhaling it."

Prof Bala hopes that the research will help to "increase the level of awareness among the general public towards the serious health effects of both active and passive smoking".

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