Wildfires are becoming more frequent in urban areas, moving beyond traditional wildland regions into cities and suburbs. This shift has increased exposure to toxic smoke, which contains harmful substances from burning plastics, metals, and other urban materials. In recent years, wildfires have been less confined to remote wilderness and more common in urban areas across the United States. As more people live near fire-prone regions, the risk of exposure to dangerous smoke and its long-term health effects is growing. Urban development has expanded into areas that are naturally more susceptible to wildfires, increasing the risk for communities. Fires in cities expose people to a range of toxic chemicals from burning metals and other substances, which are linked to long-term health risks such as higher cancer risk and cardiovascular or respiratory illnesses. For example, this summer, wildfires in Spokane, Washington, destroyed over 800 homes in a suburban neighborhood. Earlier in the season, smog from fires in Ontario affected the northeast coast. In Nevada, the Hawk Fire burned over 15,000 acres near Reno, destroying 47 homes, while last year’s fires in Los Angeles burned over 37,000 acres, mostly in densely built residential areas, displacing more than 205,000 people. The changing nature of wildfires is affecting public health in new ways. When vegetation burns, it releases fine particulate matter, known as PM 2.5, which is linked to premature death, respiratory damage, and cognitive issues. A study found that long-term exposure to smoke from wildfires increased hospitalization risk for cardiovascular diseases among older Americans. The composition of smoke has also changed due to urban materials. Fires now expose people to toxic chemicals from plastics, metal oxides, and vehicle fuel. Early research suggests these exposures may lead to serious long-term health issues, especially as people age. In 2020, California experienced its worst fire season on record, burning 4.2 million acres and releasing large amounts of PM 2.5 into the air. This led to a 12 percent increase in hospital admissions and a 43 percent rise in cardiovascular conditions in Northern California. In Oregon, 10 percent of emergency room visits were due to asthma-like conditions caused by smoke. In 2025, over 5.2 million acres burned across the U.S., and by mid-year, that number had already reached 8.5 million acres. The expansion of housing into fire-prone areas has made this problem even more severe. The USDA Forest Service found a 46 percent increase in the number of homes located in the wildland-urban interface (WUI) between 1990 and 2020, with a third of U.S. homes now in these vulnerable areas. The Los Angeles County fires in January 2025 highlighted these risks. The Palisades and Eaton fires began at the edge of the LA foothills, where dense housing meets more fire-prone terrain. As the fires spread into urban areas, the smoke became more dangerous due to the burning of over 16,000 buildings, household items, and electric vehicles. The emissions from these fires were more complex than those from traditional vegetation-only fires. According to Jackie Goodrich, a professor of epidemiology at the University of Michigan, the materials burning now are very different, with modern homes containing plastics, metals, and electronic appliances, as well as electric vehicles that include rare metals and other toxic materials. These emissions contain higher concentrations of volatile organic compounds (VOCs), metals, and carbon monoxide. PFAS, or "forever chemicals," are also released through fire extinguishing foam and damaged firefighting gear. These chemicals are associated with higher cancer risk and immune system issues. Studies after the LA fires found elevated levels of VOCs in evacuated homes even after the fires had subsided, indicating that health risks from WUI smoke exposure can persist even when homes are undamaged. Research by Goodrich and University of Arizona professor Jeff Burgess is uncovering the long-term health impacts of repeated exposure to wildfire smoke, including effects on genetic expression linked to cancer and neurodegenerative diseases. While it is unclear whether these biological changes directly lead to cancer, researchers expect to see an increase in cancer cases as exposure accumulates. Residents in the WUI face similar health risks as firefighters, potentially leading to higher rates of asthma, respiratory problems in children, and cardiovascular issues in adults.