Third-hand smoke residues a health risk, here’s why

Chemicals from tobacco smoke that get trapped in clothes, furniture and carpets can become airborne again and be circulated through office blocks, schools or other nominally smoke-free buildings.

Laboratory tests have shown that indirect exposure to tobacco residues, common on skin, clothes or surfaces, can detrimentally affect growth and immunity in mice.

Unlike direct smoking, or passive “second-hand” smoke – from being in a room or vehicle where someone is smoking – the health risks of third-hand smoke on surfaces and in the air is less well-established.

“In an empty classroom, where smoking has not been allowed for some time, we found that 29 per cent of the entire indoor air particles contained third-hand smoke chemicals,” said study author Dr Anita Avery, raising questions on how much third-hand smoke could be lingering in a non-smoking, ventilated room.

Researchers also ran laboratory trials using sealed containers, one of which was filled with cigarette smoke, and then subsequently flushed with air from outdoors.

The following day they pumped in filtered air to mimic a draft or ventilation system and measured the particle content and found that it was 13 per cent higher in the air that had passed through the smoking container.

The humid circulating air, common in communal buildings with air conditioning and heating, allows these potentially harmful chemicals to get airborne again, instead of being fixed on the surfaces of the room where smoking took place.

This could be a concern for babies in homes where a smoker sits or sleeps on furniture or carpets where these particles have settled. Moreover, third-hand smoke was found in surprising places, such as neonatal intensive care unit incubators.

“Many public areas have restrictions on smoking, including distance from doorways, non-smoking buildings and even full smoking bans,” said Dr Michael Waring. “However, these limitations only protect non-smoking populations from second-hand smoke, yet, third-hand smoke, can be as harmful, and is much more difficult to avoid,” he added.

The health risks of third-hand smoke remain unclear, but the potentially harmful chemicals associated with it could spread widely, causing harm. The findings were published in the journal Science Advances.