The California Consortium on Thirdhand Tobacco Smoke has been funded by TRDRP to conduct research on the impact of thirdhand smoke (THS) on public health. The Consortium is led by Neal Benowitz MD (PI) and Lara Gundel PhD (scientific coordinator) and administered through the University of California San Francisco (UCSF). Consortium institutions include UCSF, Lawrence Berkeley National Laboratory (LBNL), UC Riverside (UCR), University of Southern California (USC), San Diego State University (SDSU) and Portland State University (PSU). The consortium will conduct scientific research in four main areas. THS Consortium chemistry researchers will examine what happens to secondhand smoke (SHS) and thirdhand smoke when they age on indoor surfaces, including the formation of new chemicals in the environment that may be harmful to health. The Consortium analytical chemistry laboratory will develop new ways to measure human exposure to THS, including measurements of THS chemical constituents in house dust and surfaces and biomarkers in people who are exposed to tobacco smoke. Health effects of THS will also be studied, to better understand how chemicals in THS could damage genetic material in cells and affect the reproductive system. Finally, economic and policy researchers will develop risk assessment models, projections of health care costs, and strategies for dissemination of findings. This Consortium brings together investigators in a broad range of disciplines from across California, with strong research backgrounds in the characterization, exposure and health effects of tobacco smoke. It is anticipated that the outcomes of this research effort will contribute to reducing exposure of people to the disease-causing toxicants in THS.