Recent experiments on juvenile mice suggest that third-hand smoke from cigarettes, or the residual chemicals cigarette smoke leaves on indoor surfaces, could increase the chances of developing lung cancer.
As noted by Science Daily, the tests were conducted by a team of researchers from the Department of Energy’s Lawrence Berkeley National Laboratory, who published a study in 2017 that linked slight thirdhand smoke exposure to low body weight and changes to the immune system in juvenile mice. This led to a follow-up study that was documented in the journal Clinical Science, suggesting that early exposure to this type of smoke could also result in a greater risk of lung cancer in mice, meaning a higher incidence rate and greater severity.
The new study on thirdhand smoke involved a total of 24 juvenile mice aged 4-weeks-old, which were chosen because they carried a strain known to be at high risk of spontaneous lung cancer development. The mice were then placed for three weeks in a setting that simulated the equivalent of what a human toddler would be exposed to in a house with smokers — about 77 micrograms per kilogram of body weight worth of thirdhand smoke on the fabric inside the enclosure.
After 40 weeks, the mice were compared to a control group of 19 other mice, and were observed to have a higher chance of getting lung cancer, and also more likely to develop larger tumors and in greater quantity. Considering the latter two effects, the researchers also conducted in vitro studies with cultured lung cancer cells from human subjects; these also suggested that thirdhand smoke does encourage the mutation of damaged cells while allowing tumors to show up in greater number and in larger size.
Speaking to Xinhua, Berkeley Lab staff scientist Bo Hang, a co-author on the new study, said that thirdhand smoke is a “hidden risk” of cigarette smoking, adding that young children are typically the most susceptible.
“Young kids who crawl and put objects in their mouths are more likely to come in contact with contaminated surfaces, and are therefore the most vulnerable to thirdhand smoke’s harmful effects.”
Previous research has also warned about the possible link between thirdhand smoke and lung cancer, with children again at more risk than adults. According to the Mayo Clinic, people are exposed to this type of smoke when they touch or breathe the fumes from surfaces that have been contaminated by the chemical residue from cigarettes that continuously accumulates over time. Cancer-causing agents are also believed to be created when the residue blends in with “common indoor pollutants,” such as dust and dirt on furniture, walls, bedding, and other surfaces.