Thirdhand Smoke May Be More Toxic Than Secondhand Smoke


You’ve heard of the harmful effects of secondhand smoke, but a new study suggests thirdhand smoke, the residue left behind by smoking, is even more worrisome.

Thirdhand smoke causes genetic damage within human cells, according to researchers from the Lawrence Berkeley National Laboratory. Lara Gundel, a Berkeley Lab scientist and study co-author, said thirdhand smoke sticks around.

Thirdhand smoke is commonly left behind in the materials exposed to secondhand smoke. Credit: Flickr, CC BY 2.0

“This is the very first study to find that thirdhand smoke is mutagenic,” Gundel said in a press release. “Tobacco-specific nitrosamines, some of the chemical compounds in thirdhand smoke, are among the most potent carcinogens there are. They stay on surfaces, and when those surfaces are clothing or carpets, the danger to children is especially serious.”

Thirdhand smoke includes pollutants from tobacco smoke that remain on surfaces and within dust after smoking. It’s found in commonplace areas, such as residences and automobiles, and in carpets, walls, furniture, house dust and even in the hair, clothes and skin of smokers, the study said.

Ingestion, inhalation or skin contact are all ways humans come in contact with thirdhand smoke. Hugo Destaillats, a co-author and Berkeley Lab scientist, said thirdhand smoke is hard to remove from materials and surfaces.

Related: Cigarette Smoke Can Permanently Damage Your DNA

“You can do some things to reduce the odors, but it’s very difficult to really clean it completely,” Destaillats said. “The best solution is to substitute materials, such as change the carpet, repaint.”

The researchers found that exposure to thirdhand smoke for 24 hours caused significant increases in damage to human DNA. The chemical compounds in thirdhand smoke were also higher and caused more damage the longer they lingered. The thirdhand smoke was tested for genotoxicity, a critical mechanism responsible for several kinds of cancer caused by smoking, the study said. The scientists measured for genotoxicity by focusing on the DNA damage that was observed.

“Until this study, the toxicity of thirdhand smoke has not been well understood,” said Bo Hang, a Berkeley Lab scientist and co-author. “Thirdhand smoke has a smaller quantity of chemicals than secondhand smoke, so it’s good to have experimental evidence to confirm its genotoxicity.”

Credit: ebrkut/Flickr, CC BY-ND 2.0

The authors noted that a significant characteristic of thirdhand smoke is that the surface-absorbed residues can go through chemical transformations as they interact with the atmosphere to create even more toxic substances. Nicotine reacts with the ozone to create a handful of irritants, including tobacco-specific nitrosamines, known as TSNAs.

One TSNA, called NNK for short, was shown to increase as secondhand smoke ages into thirdhand smoke. Another, known as NNA, was found to be absent in secondhand smoke, but was identified as the main TSNA within thirdhand smoke, the authors wrote.

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NNA is not well understood within the scientific community, and Hang said he hopes to conduct more research into understanding the substance and its effect on human DNA. The study is the first to research the genotoxicity of thirdhand smoke, the authors wrote.

“[The study’s] findings are highly relevant to addressing the gap in knowledge about the health impacts of THS because genotoxicity is associated with development of diseases,” the authors wrote.