Cigarettes and other tobacco products produce chemicals that linger in indoor environments, putting all other occupants in harm’s way. (Credit: Mumemories/iStock)

Scientists at Berkeley Lab first identified thirdhand smoke as a potential health hazard a decade ago. The newest study develops more quantitative insights into its long-term health risks. Investigators found that concentrations of toxic chemicals lingering in indoor environments where cigarettes have been smoked can exceed risk guidelines from the State of California, meaning that non-smokers can be exposed to health risks by living in contaminated spaces.

Researchers from the Biological Systems and Engineering (BSE) division, Bo Hang, Jian-Hua Mao, Altaf Sarker, and Antoine M. Snijders, contributed to the effort along with other Berkeley Lab groups and researchers at UC San Francisco, UC Riverside, and San Diego State University.

Figure showing the levels of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a strongly carcinogenic compound across multiple pathways. (Credit: 2022 Tang, et al)

The study found that thirdhand smoke exposure through multiple pathways – inhalation, dust ingestion, and skin absorption – under typical indoor conditions can result in specific carcinogenic compounds that exceed health guidelines known as “No-Significant Risk Level” established by California’s Office of Environmental Health Hazard Assessment as part of Proposition 65. These cumulative exposures can contribute to an elevated cancer risk.

“Next steps for this research will explore in more detail the mechanisms of adverse health effects associated with tobacco and cannabis residues, effective remediation strategies, and translation of scientific findings to tobacco control practice,” said co-author Neal Benowitz, a UCSF professor who leads the collaborative group.