47 New research from UTHealth Houston has found that firefighters experience measurable biological changes in their blood and urine within 24 hours of fighting a fire. The findings could help identify early biological signals associated with cancer risk, which is the leading cause of death among firefighters. The study, published in Environment & Health, was led by Jooyeon Hwang, PhD, an associate professor at UTHealth Houston School of Public Health. Previous research by Hwang found that repeated exposure to harmful substances in fire smoke, including particles, heavy metals, and polycyclic aromatic hydrocarbons, can cause long-term health problems such as cancer. Research from the Centers for Disease Control and Prevention and the National Institute for Occupational Safety and Health found that firefighters have a 9% higher risk of being diagnosed with cancer and a 14% higher risk of dying from the disease. Researchers analysed blood and urine samples from 30 firefighters collected before and after fire exposure to examine how the body responds in the immediate aftermath. At baseline, the team identified and quantified 330 protein groups in blood serum and 1,085 in urine. After exposure, 75 proteins in urine had changed significantly, compared with 10 in blood serum. Urine showed the broadest and most sensitive changes. Several of the altered proteins were associated with cancer-related pathways, including those linked to small cell lung cancer. The researchers also identified coordinated changes in four key proteins: LAMA4, LAMC1, VWF, and B2M. Within 24 hours of exposure, the proteins changed in a pattern that closely mirrored early cancer pathways. The findings suggest that toxic smoke may trigger immediate cellular stress associated with cancer and temporarily weaken the body’s natural immune defences against tumour development. “Firefighters put their lives on the line to protect our communities, but they return from the fireground carrying an invisible toxic burden that silently increases their risk of cancer,” said Hwang, who also serves as deputy director of the Southwest Center for Occupational and Environmental Health and programme director of Industrial Hygiene and Exposure Sciences at the School of Public Health. “Our study shows that we do not have to wait years for chronic illnesses to manifest. The body’s proteins react almost immediately. By demonstrating that urine is a remarkably sensitive, noninvasive way to capture these early cellular distress signals, we are opening the door to detecting risk long before a disease develops. This isn’t just about collecting data. It is about developing the tools we need to safeguard the health of our first responders, firefighters.” Researchers hope to investigate whether these protein changes persist or develop differently with repeated exposure through larger longitudinal studies, including the Texas Firefighter Cancer Study. “Ultimately, we hope to integrate advanced biomarker screening into standard occupational health assessments, like the National Fire Protection Association 1580 guidelines. By establishing routine, molecular-level screening and personalised hydration protocols to help clear these toxins from the kidneys, we can transition firefighter medicine from a reactive model to proactive, precision-based prevention,” Hwang said. The Texas Firefighter Cancer Study is funded with $5 million from the Texas Legislature and aims to improve early detection among more than 55,000 firefighters in the state. Between 2019 and 2023, the number of firefighters in Texas diagnosed with cancer increased nearly fivefold, from 19 cases to 91, according to the Texas Commission on Fire Protection. The findings suggest that urine testing could provide a practical, non-invasive way to monitor the body’s acute response to fire smoke. Further research will examine how protein patterns change with repeated exposure and whether routine screening could help reduce long-term cancer risk among firefighters.