Exposure to thirdhand smoke via clothing, indoor spaces raises cancer risk: Study

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Just like secondhand smoke, exposure to thirdhand smoke can be dangerous for one’s health. A new study found that thirdhand smoke exposure, through lingering nicotine in indoor spaces and smokers’ clothing, can raise one’s risk of contracting cancer.

The new study, published by a team at the Lawrence Berkeley National Laboratory, found that non-smokers living or staying in places contaminated by nicotine and cigarette smoke can potentially expose them to toxic chemicals leading to possible major long-term health risks.

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A previous study conducted by the same team looked at the dangers of residual nicotine in the air after vaping or smoking indoors. Results showed that indoor surfaces can absorb the toxins and react with another airborne compound called nitrous acid (HONO). This combination can potentially create cancer-causing compounds called tobacco-specific nitrosamines (TSNAs).

Accumulated nicotine on household surfaces can continuously generate TSNAs, long after smoke clears the room.

“Since we first described this chemistry in 2010, several studies have further illustrated the presence of TSNAs on indoor surfaces and settled dust. In this new article, we integrated the new information produced over the past decade with our most recent results, to estimate the daily doses to which people may be exposed when living in homes contaminated with thirdhand smoke,” the study’s principal investigator and chemist at Berkeley Lab Hugo Destaillats said in a statement.

TSNAs can enter the body in various ways, including direct inhalation or by ingesting dust mixed with the carcinogenic compound. Although it is not completely understood yet, there has been some evidence that TSNAs can enter through the skin due to contact with contaminated surfaces or polluted air.

For example, this can happen through sleeping on bedsheets where someone had previously been smoking or through epidermal chemistry where nicotine on the skin reacts with environmental HONO to form TSNA directly on the skin’s surface.

“Nicotine is released in large amounts during smoking, and it coats all indoor surfaces, including human skin,” lead study author Xiaochen Tang, who is also a researcher at the Berkeley Lab, said.

“We found that the presence of skin oils and sweat on model surfaces led to a higher yield of TSNAs in the presence of HONO, compared with clean surfaces,” Tang added.

Three different TSNAs were formed in this reaction, two of which (identified by the acronyms NNK and NNN) are known carcinogens. There is less toxicological information for the third one, NNA, which is not present in tobacco smoke.

“We present additional evidence of the genotoxicity of NNA by evaluating its effect on cultured human lung cells,” co-author Bo Hang from Berkeley Lab’s Biosciences Area said.

“Contact with NNA led to DNA damage, including double-strand breaks, the most deleterious genotoxic outcome.”

The study also found that exposure through all of these pathways – inhalation, dust ingestion, and dermal absorption – under typical indoor conditions can result in NNK doses that exceed health guidelines known as “No-Significant Risk Levels” established by California’s Office of Environmental Health Hazard Assessment.

The findings can be found in the journal Environmental Science and Technology.

Alongside Berkeley Lab scientists, co-authors on this work include collaborators from University of California San Francisco, University of California Riverside, and San Diego State University.

These teams are members of the California Consortium on Thirdhand Smoke, funded by the Tobacco-Related Disease Research Program, which is managed by the University of California.

“These findings illustrate the potential health impacts of thirdhand smoke, which contains not only TSNAs but hundreds of other chemicals, some of which are also known carcinogens,” co-author Neal Benowitz, professor from the University of California San Francisco who leads the Consortium said.

The researchers will next explore “mechanisms of adverse health effects associated with tobacco and cannabis residues, effective remediation strategies, and translation of scientific findings to tobacco control practice.”

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