Researchers at Lawrence Berkeley National Laboratory, or Berkeley Lab, found that “thirdhand smoke,” or THS, increases the chances of lung cancer in mice — a finding that can translate to humans.
The study, titled “Short-term early exposure to cigarette smoke increases lung cancer incidence in mice,” was spearheaded by Bo Hang, Jian-Hua Mao and Antoine Snijders. According to Snijders, the goal of the study was to test the impacts of THS, and the study says the carcinogenic potential of THS had been previously untested.
THS is a toxic residue left behind in areas long after a cigarette has been smoked and can be found on surfaces like carpets, or in areas like cars and rooms. Mao said THS can subtly be transferred via skin contact and through the mouth, among other means of transmission.
“People think you can wash it off the walls or the carpets to get rid of TH smoke, but this isn’t true,” Snijders said.
According to Snijders, the study was conducted by exposing mice to cages contaminated with THS and analyzing the instances of lung cancer in those mice compared to a control group of mice who were never exposed to THS. The scientists found that the mice exposed to THS had a higher incidence of lung cancer compared to the control group.
This study was a continuation of previous research conducted by the same scientists, according to Snijders. The previous study linked smoke exposure in mice to changes in body weight and immune system functions.
“We didn’t know back then what the long-term changes would be, but here we explored that,” Snijders said.
When applying the results of this study to humans, Mao said conclusions should be drawn case by case. The researchers used a breed of mice that is highly sensitive to lung cancer, and this could have contributed to why the mice exposed to THS developed lung cancer, according to Snijders.
In a more resistant breed of mice, Snijders said the researchers didn’t see the same trend, meaning that the impacts of THS on humans should vary based on genetics and may differ among individuals.
Additionally, the study only tested THS exposure on mice before they reached adolescence, indicating a heightened threat to human children.
“Although current evidence, including animal studies, suggests that THS may be a potential health threat to infants and young children who are in smokers’ homes, virtually nothing is known about the long-term effects of early THS exposure on tumor development in later life,” the study reads.
In terms of potential ways to fix the problem THS poses to society, both Mao and Snijders said policymakers should use Berkeley Lab’s research to work on solutions. One example of a policy change, Snijder suggested, was to encourage apartment owners to replace carpeting and curtains at certain intervals.