Cigarette smoke, like murder, is classified in degrees. First-hand smoke is smoke inhaled by smokers, second-hand is exhaled smoke and other toxins from a burning cigarette inhaled by non-smokers. Third-hand smoke is “leftover” smoke that clings to surfaces and dust and gives closed spaces the distinctive dank tobacco smell.
Smug non-smokers like me shun the first, avoid the second and are oblivious to the third. Bad call.
Cigarette smoke residues harm nonsmokers as much as smoking, reported the first animal study on the effect of third-hand smoke. Third-hand smoke persists in houses, apartments and hotel rooms after smokers move out and gets more toxic over time. Re-emission of nicotine from contaminated indoor surfaces causes nicotine exposure levels similar to that of smoking, report researchers from the University of California, Riverside, in the journal PLOS ONE.
“We studied, on mice, the effects of third-hand smoke under conditions that simulated its exposure of humans. We found significant damage occurs in the liver and lung. Wounds in these mice took longer to heal. Further, these mice displayed hyperactivity,” said Manuela Martins-Green, a professor of cell biology, who led the study. Exposing mice to third-hand smoke in the lab triggered alterations in multiple organ systems and excretion of a tobacco-specific carcinogen.
In the liver, it raised lipid (fat) levels and contributed to non-alcoholic fatty liver disease, a precursor to cirrhosis and cancer and a potential contributor to heart disease. In the lungs, third-hand smoke triggered excess collagen production and raised inflammatory cytokines (small proteins involved in cell signalling), both early signs of fibrosis and inflammation-induced diseases such as asthma and chronic obstructive pulmonary disease. The mice also displayed the kind of slow healing observed in human smokers who have gone through surgery.
Finally, behavioural tests showed hyperactivity. “The latter data, combined with emerging associated behavioural problems in children exposed to second- and third-hand smoke, suggests that with prolonged exposure, children may be at risk for developing more severe neurological disorders,” said Martins-Green.
Tobacco kills up to half of its users, causing 6 million premature deaths – one death every 6 seconds – each year. More than 6 lakh of those who die are non-smokers who have been exposed to second-hand smoke.
Tobacco smoke contains over 4,000 chemicals in the form of particles and gases. Many toxic gases are present in higher concentrations in “sidestream” smoke (from the burning tip of the cigarette) than “mainstream” (smoke inhaled by smokers) and nearly 85% of the smoke in a room results from sidestream smoke. The particulates include tar (itself made up of many chemicals), nicotine, benzene and benzo(a)pyrene.
The gases include carbon monoxide, ammonia, dimethylnitrosamine, formaldehyde, hydrogen cyanide and acrolein. Almost all have marked irritant properties and about 60 are known or suspected to cause cancer.
Some of the immediate effects of passive smoking include eye irritation, headache, cough, sore throat, dizziness and nausea. It causes a sharp decline in lung function in adults with asthma, while triggering new cases of asthma in children whose parents smoke indoors.
Short-term exposure also has a startling effect on the heart in non-smokers -- just minutes’ exposure reduces blood flow to the heart, raising risk of heart disease by 25%, reported the British Medical Journal. A major review by the UK’s Scientific Committee on Tobacco and Health concluded that passive smoking is a cause of lung cancer and heart disease in adult non-smokers, and a cause of respiratory disease, cot death, middle ear disease and asthmatic attacks in children.
The International Agency for Research on Cancer says passive smoking causes lung cancer in non- smokers. Research has shown that children living with one or two adults who smoke indoors, are absent 40% more days from school due to illness than children who live in smokefree homes. Passive smoking increases the risk of lower respiratory tract infections such as bronchitis, pneumonia and bronchiolitis in children.
Much like smoking, exposure to second and third-hand smoke during pregnancy harms the unborn baby, lowering birth weight and reducing lung function.
With smoking being banned in public places and most smokers choosing to stub out cigarettes in the company of non-smokers, the threat to health remains from contaminated surfaces, including clothes. Smokers, perhaps, should keep this in mind before taking cigarette breaks when in the company of children, whose developing bodies are hardest hit from exposure to toxins.