SDSU research leads to law safeguarding homebuyers against thirdhand smoke exposure

Driven by the work of San Diego State University researchers, a new law adds thirdhand smoke to the list of environmental hazards that must be disclosed when a home is sold in California. 

Authored by Assemblymember Liz Ortega (D, San Leandro), passed unanimously in both houses of the state Legislature and signed into law by Gov. Gavin Newsom in October, Assembly Bill 455 takes effect Jan. 1, 2026. 

Thirdhand smoke is the chemical fingerprint that lingers indoors long after smoking and vaping have ceased. The toxic residue clings to surfaces such as walls, carpets, and upholstery, allowing pollutants and carcinogens — many of which the state has identified as capable of causing cancer, birth defects, or reproductive harm — to damage the health of inhabitants.

Under AB 455, the presence of the residue must be disclosed in single-family residential transactions.

Researchers from SDSU’s Thirdhand Smoke Resource Center, University of California San Francisco and Lawrence Berkeley National Lab have provided scientific evidence demonstrating the detrimental effects of this residue. The effects of thirdhand smoke are particularly harmful for children, the elderly and those who are immunocompromised. 

Since 2010, these researchers have worked together as the California Thirdhand Smoke Research Consortium, funded by the California Tobacco-Related Disease Research Program. These experts, from fields such as public health, environmental chemistry, pharmacology, psychology, communication and biology, collaborate to conduct comprehensive thirdhand smoke studies and educate others on the toxicity of this residue.

The consortium’s members consulted with the California Association of Realtors, as well as state officials and agencies such as the Departments of Public Health and Real Estate, to share their research insights and discuss new policy options to further protect people from thirdhand smoke. This summer, Georg E. Matt, SDSU psychology professor and director of SDSU’s Thirdhand Smoke Resource Center, shared the science behind thirdhand smoke pollution and exposure at Assembly and Senate Committee hearings in Sacramento.

"By recognizing thirdhand smoke as an environmental hazard that requires disclosure, California has expanded the scope of tobacco regulation,” said Matt. “Just as we warn about lead paint or asbestos, Californians will now be warned if a home may expose them to toxic tobacco smoke residue. As a homebuyer, it is important to know this information before you make an offer."

In November, Matt and Neal L. Benowitz, emeritus professor of medicine at UCSF, published a paper in the Journal of the American Medical Association outlining the stipulations of the landmark bill and its importance in protecting consumer health.

“Thirdhand smoke is not just an irritating smell in the home. It indicates that the home is contaminated with potentially harmful chemicals derived from tobacco smoke,” Benowitz said.

“Homebuyers deserve to know if their future homes are contaminated and be able to decide about the costs of removing these chemicals. AB 455 will make informing buyers about the hazards of thirdhand smoke a reality.”