Project Summary Thirdhand smoke (THS) is the particulate matter and residue left behind on surfaces from secondhand smoke (SHS) by smokers and those exposed to SHS. Over 18% of US adults smoke, with higher prevalence (23-42%) in low-SES populations, making THS a distinct public health hazard, especially for the 22% of all infants and children exposed to SHS and THS in their homes. THS contains and forms carcinogens and other toxicants that damage DNA, adversely affect cognitive functioning, and hinder respiratory development and wound healing. THS is difficult to remove from indoor surfaces and spreads easily from the breath, clothes, and hands of SHS-exposed individuals. It reacts easily with other pollutants to form carcinogens and exposes individuals, especially children, through multiple routes (e.g., dermal uptake). Repeated exposures of re- suspended particulate matter and THS returning to a gaseous state occur for months-to-years after a cigarette is extinguished. Studies have documented the presence of THS in homes, cars, and hotels with partial and total smoking bans. With the exception of our recently published pilot data, indicating THS contamination in a neonatal intensive care unit (NICU), healthcare settings with strict non-smoking policies and high numbers of visitors who smoke have been unexplored. The most fragile hospital populations are housed in the intensive care units. In particular, infants born prematurely (as early as 23 weeks gestation) and at extremely low birth weights (<1000 grams [2.2 pounds]) are arguably the most vulnerable. Parents visiting the NICU are disproportionately of lower socio-economic status and thus smoke at high rates (>26%), resulting in significant health disparities. Premature infants with underdeveloped respiratory systems often require mechanical ventilation and are at risk for numerous respiratory and other illnesses (e.g., bronchopulmonary dysplasia, asthma) during extended hospitalizations often spanning months. THS may negatively affect both acute and chronic health outcomes of NICU infants. The central aim of this small grant proposal is to characterize THS present in a large, urban hospital NICU using well-established, highly sensitive surface nicotine wipes. Our pilot data indicate that nicotine is detectable on NICU surfaces and in NICU infants? urine. This initial work will determine the extent to which visitors (N=210) and staff (N=171) transport THS to the NICU and will quantify the amount of THS deposited in the NICU by sampling nicotine found on surfaces (N=80), across smoking and nonsmoking households. Infant urine cotinine will also be collected and quantify nicotine transmitted to the infant. A novel sub-study to explore the efficacy of hand cleaning to remove THS will also be conducted (n=20). Quantifying THS in a NICU caring for vulnerable infants will demonstrate THS?s pervasiveness and support further research to eliminate contamination via intervention and policy change. Results of this initial study will provide the impetus for larger clinical studies to determine acute and chronic effects of early exposure to nicotine-related carcinogens.