A new study by Drs. Myung-Bae Park and Chhabi Lai Ranabhat from Pai Chai University in the Republic of Korea, found that children of parents who smoke were exposed to tobacco smoke pollutants even when their parents did not smoke within the home. The research, based on Korean national survey data, adds to the mounting evidence that home smoking bans cannot fully protect children from exposure to toxic second- and thirdhand smoke.

June 2, 2021

By Leta Dickinson

Passive smoking exposure: You may not smoke, but chances are, between second- and thirdhand smoke exposure, you are exposed to some toxic tobacco chemicals. While many countries are working to strengthen clean air and tobacco control policies, the continued widespread use of tobacco products and persistence of tobacco smoke residue means that toxic thirdhand smoke poses a health risk to many of us.

Drs. Myung-Bae Park and Chhabi Lai Ranabhat from Pai Chai University in the Republic of Korea recently investigated how South Korean parents’ smoking habits contributed to their children’s tobacco exposure levels primarily through thirdhand smoke.

Using results from the 2014-2018 Korean National Health and Nutrition Health Examination Survey (KNHANES), the researchers identified over a thousand children aged 6-18 who reported that their parents did not smoke inside the home. They then measured cotinine levels in the children and their parents and. Cotinine is a component of tobacco that can be detected and measured in bodily fluids like blood, urine, and saliva shortly after tobacco exposure. The higher the cotinine level, the higher the exposure to tobacco.

The results were, for the most part, unsurprising, Dr. Myung-Bae Park from Pai Chai University says. “Children from families where one or both parents smoked had higher levels of cotinine than children from nonsmoking families. Similarly, when both parents smoked, the children’s cotinine levels were higher than when only one parent smoked.” What did surprise Dr. Park was that the children’s cotinine levels were more closely related to their mother’s cotinine and smoking habits than to their father’s. In fact, children who only had a father that smoked had lower cotinine levels than children who only had a mother that smoked, even fathers in this study smoked 2.6 times more cigarettes per day than mothers.

Dr. Park explains why this could be: “Mothers are more likely to impact smoking exposure in the home because they are more likely to spend time with their children in Korea and other East Asian countries where Confucianism is widespread.”

Another unexpected result was that younger children had higher cotinine levels than older children. Specifically, the children under age 12 had the highest cotinine levels when compared to children between 12 and 15 and between 15 and 18.

“The younger the children are, more time they spend at home,” Dr. Park says. “And so, the more time they spend with their parents.”

South Korea has had tobacco control laws in place since 1995, which were expanded to prohibit smoking in and around schools in 2006. Thus, the older children who have longer school days and extracurriculars through school are more likely to spend their time in smoke-free areas, which may explain the age-dependent cotinine level differences.

While this study offers valuable insights into how parents’ home smoking habits affect their children, it is impossible to precisely pinpoint the source of tobacco exposure. Self-reported survey responses are always subject to error, especially when the questions are of a sensitive nature, like smoking habits. Dr. Park also emphasizes that cotinine is linked to tobacco exposure from all sources, whether first-, second-, or thirdhand. While he hopes that his study is primarily measuring cotinine from thirdhand smoke exposure, there is no way to know for sure.

This is the first study to measure passive smoke exposure in the South Korean population, but previous studies in the United States and U.K. have found similar patterns between parent and children tobacco exposure. This growing body of evidence indicates that thirdhand smoke is a pressing international health concern that requires immediate policy change and public attention to address. The existing tobacco control and clean air policies are not sufficient. The longer tobacco use continues, the more pervasive and difficult its chemical residue will be to remove.  

Dr. Park offers this advice: “If your friends or parents smoke, strongly recommend they quit smoking. It’s impossible to avoid exposure.”

Click here to read the research study.