Passive smoking happens when cigarette smoke saturates an environment such that non-smokers in the same room are forced to inhale smoke from tobacco used by other people. Also known as second hand smoke (SHS) or environmental tobacco smoke (ETS) inhalation, passive smoking is more prevalent in confined indoor spaces, although it can also occur in open spaces.
Third hand smoke (THS), on the other hand, is the surface-mediated chemical transformation of nicotine. THS comes from nicotine particulates from SHS and ETS that settle on exposed surfaces; these particulates react to the pollutant nitrous acid that is a common in indoor air and transform into tobacco-specific nitrosamines (TSNAs). The formation of TSNAs was considered alarming, as nitrous acid is a common pollutant in ambient household air, particularly those with unvented gas appliances.
The presence of harmful substances as a result of tobacco smoking has been known for years, but it is only recently that serious research was conducted on the particulate residues left on surfaces and the chemical transformation of the same when exposed to different conditions.
Here’s a scenario that is useful in comparing the three smoke types. Imagine lighting up a cigarette in a closed elevator; every time you puff on the cigarette, you take in first hand (mainstream) smoke. The smoke from the burning end of the cigarette (sidestream smoke) and the smoke that comes out as you exhale will pervade the air as second hand smoke. Other people in the elevator will involuntarily inhale some of that smoke, putting them in the same level of risk as the smoker. The rest will dissipate away in a matter of minutes, depositing nicotine traces on all exposed surfaces. If there is nitrous acid in the elevator’s ambient air, the nicotine traces would chemically transform into TSNAs that may later find their way into human bodies.
Dangers of SHS
Numerous studies have been published validating the harmful effects of involuntary smoking to specific segments of the population. In 2000, it is estimated that 3,000 deaths from lung cancer and 62,000 fatalities from coronary heart disease for non-smokers were caused by both SHS and ETS.
In children, exposure to involuntary smoking was the major factor in respiratory diseases, middle ear infections, sudden infant death syndrome, and premature or low birth weight for newborns of smoking mothers. The relative risk of contracting asthma, bronchitis, cancers, cognitive impairment and other diseases frequently associated with direct smoking were significantly higher for non-smokers exposed to SHS compared to the general population.
Dangers of THS
Although research on surface-mediated transformation of nicotine is relatively recent, TSNAs have long been known as carcinogenic. For example, the nitroamine NNK may induce mutations and breaks in DNA strands and it has long been a potent carcinogen that induces lung tumors in research animals.
TNSAs are absorbed by humans through inhalation or ingestion of nitroamine-laden dust, or contact with people’s skin and clothing. Infants and children are specially vulnerable, as they are in frequent contact with dust and surfaces, and have a higher respiration rate and lower body weight.
While the amounts of TNSAs that make their way into human bodies may be minute, and since long-term hazards of exposure to such carcinogens are still being studied, it is always wise to err on the side of caution and minimize exposure to THS at this time.
Stricter regulations on cigarette products
Since the dangers of smoking came to light, quite a number of measures to curb smoking have been initiated. These include banning tobacco advertisements in media, prohibition of smoking in public places and intensive awareness campaigns on the dangers of smoking.
Still the worldwide figures for smoking are increasing due to the rising number of smokers from developing countries. Thus, there is a need for more and stricter regulations, at the very least to mitigate effects of SHS, ETS and THS on non-smokers.
Self-restriction in homes, and strict implementation of no-smoking policies in workplaces and common areas are great ways to lessen exposure to smoke. But even outdoor smoking is not risk-free, as nicotine traces cling to the smoker’s hair, skin and clothing, which will turn into carcinogenic TSNAs once the smoker enters a room with ambient nitrous acid.
The only long-term remedy therefore, is to make people stop smoking. It helps that there are quite a number of ways to help smokers quit smoking nowadays, including use of chemical substitutes, hypnosis and other innovative ways.
State-Specific Prevalence of Current Cigarette Smoking Among Adults, and Policies and Attitudes About Secondhand Smoke —United States, 2000
Study reveals dangers of nicotine in third-hand smoke
Beliefs About the Health Effects of "Thirdhand" Smoke and Home Smoking Bans
Formation of carcinogens indoors by surface-mediated reactions of nicotine with nitrous acid, leading to potential thirdhand smoke hazards
Tobacco Smoke Carcinogens and Lung Cancer