Sticky toxic residue left behind by cigarettes is an invisible threat that can cause health problems for non-smokers and even damage DNA, doctors warn.
While the dangers of passive smoking are widely recognised, unseen thirdhand smoke residue is penetrating homes, cars and workplaces to compromise immunity and respiratory systems ― particularly in children.
Nicotine from smoke interacts with nitrous acid, a common molecule found in the air we breathe, and leaves a trail of three compounds ― two of which are carcinogenic.
The NNK, NNA and NNN compounds form a trio of tobacco-specific nitrosamines and create third-hand smoke that can persist in homes years after a smoker has left.
Risk for non-smokers
Scientists at the US Department of Energy’s Lawrence Berkeley National Laboratory in California recently studied the amount of chemicals in the home of a regular smoker.
Results published in the journal Environmental Science and Technology found the levels recorded exceeded California’s safety guidelines, and showed potential long-term health risks for non-smokers in homes contaminated with third-hand tobacco smoke.
Dr Ayman Ahmed, critical care specialist at Salma Rehabilitation Hospital, at Sheikh Khalifa Medical City, said third-hand smoke was an often overlooked health risk.
"Residual contamination particles can remain on surfaces in any room for some time, and can worsen existing issues like asthma, bronchial problems or anyone who is immunocompromised or with chronic disease,” he said.
“It can remain on our clothes when we leave a smoky place and it can stay in our homes, people are not aware of the health impact of this ― just smoking and passive smoking.
“Carcinogens are cancer-causing long term, this is something we already know and it does not just affect the smoker.
"It is responsible for a specific group of cancers and can be damaging for those at high risk or with allergies.
“Children of smokers are particularly at risk from third -hand smoking.
“They are the most affected because they have low immunity and their respiratory system is not yet well formed.”
Residue on skin and animal fur
Air-conditioning systems in cars and the home can circulate the toxins that become embedded for some time.
Although toxins from cigarettes seem to go up in smoke, they often land on surfaces such as tabletops, bedding, toys, floors, car upholstery, or any other place where a smoker has exhaled.
Residue sticks to the skin of people and their pets, and can be ingested, or gets released into the air to be re-inhaled.
Researchers from the Thirdhand Smoke Research Consortium at the University of Californian suggested residue can be 50 times higher in the apartment of a former smoker than in a new apartment with active smokers.
A study referenced by the group revealed broken strands in the DNA of lung cells of mice exposed to nicotine on their skin, to illustrate the damage done at a cellular level by cigarette toxins.
The consortium, formed in 2011, recommends several risk-reduction measures for non-smokers.
They include restricting smoking areas in the workplace and at home and removing residue from older smoking hang-outs by deep cleaning surfaces and upholstery.
Because toxins cannot be eliminated by airing out rooms or using air conditioners, specific cleaning methods are needed to sanitise contaminated areas.
“These toxins can last many months or even years on surfaces, it really depends on how well it is ventilated ― it is a hidden killer,” said Dr Trilok Chand, head of respiratory medicine, Burjeel Hospital in Abu Dhabi.
“Third-hand smoke cannot be seen, so it is often ignored.
“If someone is moving to a new house, it is worth finding out if the previous owner was a smoker to bring in deep cleaning to reduce these kinds of toxins."
Cigarette smoke typically contains more than 4,000 toxic chemicals.
Exposure is most dangerous for babies, children, the elderly, and people with health conditions such as respiratory issues or autoimmune diseases.
"Many of these toxins are cancerous, and that is the main issue ― causing cancer of the lung, mouth or larynx," Dr Chand said.
"Federal law to restrict smoking in the workplace is significant, and it works, but it must be enforced.”