What is thirdhand smoke?

Author: Chen Meilin Guangxi Academy of Medical Sciences Guangxi Zhuang Autonomous Region People's Hospital

Reviewer: Jia Yongxing, Executive Editor of Popular Medicine Magazine, Shanghai Science and Technology Press

Walking down the street or in a restaurant, it is not hard to see smokers puffing away. Tobacco seems to be invading our lives in all directions. Currently, there are more than 300 million smokers in my country, and 700 million people are exposed to secondhand smoke. The huge harm of tobacco to health causes more than 1 million deaths in China every year, which exceeds the total number of deaths from AIDS, tuberculosis, traffic accidents and suicides[].

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We are all familiar with first-hand and second-hand smoke, but is this the first time you have heard of third-hand smoke?

What is thirdhand smoke?

Before understanding third-hand smoke, we need to know what first-hand smoke is and what second-hand smoke is.

First-hand smoke refers to the tobacco smoke that smokers inhale into their lungs. Second-hand smoke is a mixture of smoke and other substances released by the burning end of tobacco and exhaled by smokers, which enters the air and can be inhaled by other people.

Thirdhand smoke is best at "lurking" and "fighting a protracted war." Thirdhand smoke is composed of pollutants that are deposited indoors when smokers smoke. It can adhere to surfaces such as clothing, furniture, carpets, walls, and even smokers' hair and skin. These pollutants can adhere to objects and remain for days or even months, continuously endangering human health. Thirdhand smoke will accumulate over time and penetrate deep into floors and walls, making it difficult to remove even with window ventilation and wiping. In addition, thirdhand smoke that adheres to the surface of objects will re-emit into the air, react with oxidants, and produce secondary pollutants with other compounds. Nicotine that adheres to the surface of objects reacts with nitrous acid in the air to form nitrosamines, a tobacco-specific carcinogen.

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Is third-hand smoke harmful to the human body?

The harm of first-hand smoke is well established, and second-hand smoke is equally harmful. It is reported that exposure to second-hand smoke can cause asthma, lung cancer, coronary heart disease, etc. [1]. Non-smokers exposed to second-hand smoke will also increase the risk of smoking-related diseases.

Is third-hand smoke harmful to the human body? Although the current exploration of third-hand smoke is still incomplete, some studies have shown that third-hand smoke may have a range of health effects, including negative effects on the liver and lungs, as well as slowed wound healing and mental overactive behavior. Other studies have found that third-hand smoke increases the risk of lung cancer in mice, and compared with inhaled second-hand smoke, third-hand smoke can be absorbed through the skin and has a negative impact on health.

Compared with adults, children are more likely to be exposed to third-hand smoke because they stay at home more often and are more likely to come into contact with furniture and carpets contaminated by third-hand smoke when crawling and playing. In addition, they may also increase the possibility of third-hand smoke exposure by maintaining close physical contact with smoking parents, because smoking parents' clothes, hair and skin are often covered with third-hand smoke.

How to avoid the impact of third-hand smoke?

The most effective way to prevent thirdhand smoke exposure is to avoid it altogether. If you are a nonsmoker, this may require staying away from smokers’ homes and smoking areas. If you smoke, thirdhand smoke is one of the many reasons you should quit.

As a smoker, the way to prevent the spread of thirdhand smoke contaminants to others is to change clothes frequently and wash hands frequently. This is especially important before contact with infants and children.

References

[1] Wang Chen, Xiao Dan, Chi Hui. Summary of “China Smoking Health Report 2020”. Chinese Journal of Circulation, 2021, 36(10): 937-952.