Researchers analyzed blood and urine samples from 30 firefighters before and after fire exposure to better understand how the body immediately responds. (Credit: UTHealth Houston)
A Day After the Fire, Firefighters’ Blood and Urine Tell a New Story
In A Nutshell
- Firefighters showed measurable biological changes in both blood and urine within 24 hours of fighting a real fire, according to a new study.
- Researchers compared samples from 30 Oklahoma firefighters taken after real fires against each firefighter’s own fire-free baseline.
- Urine showed far more of these changes than blood did, revealing 75 altered proteins compared to 10 in blood, several tied to cancer-related pathways.
- The findings are early and exploratory. They don’t show that a single fire causes cancer, only that smoke exposure leaves a detectable molecular fingerprint in both fluids worth tracking over time.
A single fire call may leave a biological trace in both blood and urine within a day. That’s the finding from a new study published in Environment & Health and led by researchers now at UTHealth Houston, tracking proteins in Oklahoma firefighters’ body fluids after real emergency calls, compared against a baseline collected when firefighters had gone at least a week without responding to a fire.
Within 24 hours of battling a blaze, firefighters showed measurable shifts in dozens of proteins across both fluids, several already tied to cancer in scientific research, raising the possibility that biomarker testing could one day give researchers a new molecular layer for tracking those changes.
Firefighters develop certain cancers at higher rates than the general population, including mesothelioma, bladder, prostate, and melanoma, and an American Cancer Society study found elevated death rates from skin, kidney, pancreatic, and prostate cancers in this group. Repeated exposure to toxic chemicals released when buildings and their contents burn drives that risk, and what remained unclear was how quickly those exposures leave biological footprints.
Firefighters’ Samples Were Compared to Their Own Fire-Free Baseline
Researchers recruited 30 firefighters from Oklahoma, volunteers and career professionals alike, and collected post-fire blood and urine samples within 24 hours of firefighting, then compared them with baseline samples collected after at least seven fire-free days, since fires happen without warning and a single event couldn’t be tracked start to finish. Participants needed to be at least 18, have at least one year of experience, and own their own gear. The group was mostly male (93.3%), mostly white (96.7%), averaging 40 years old, and half were classified as having obesity.
Of the 30 participants, 20 provided paired urine samples before and after a fire; blood was unavailable for four of them, leaving 42 blood samples and 50 urine samples for analysis. Researchers used mass spectrometry, a technique that can identify and compare large numbers of proteins from biological samples, to catalog over 1,000 protein groups in urine and 330 in blood, a gap hinting urine would capture a richer picture of the body’s response.
Urine and Blood Both Showed Protein Changes, But Urine Showed More
When comparing samples taken before and after a fire, urine showed 75 significantly altered proteins, 43 that increased and 32 that decreased. Blood showed just 10, one that increased and nine that decreased. After stricter filtering to keep only proteins detected consistently across most samples, 47 urine proteins and 7 blood proteins remained as the strongest candidates tied to fire exposure.
Only one protein, fibrinogen gamma chain, changed in both fluids: up in urine, down in blood, and prior research has linked it to markers of lung disease and kidney scarring. Twelve proteins matched a public database of cancer-associated proteins, several tied to how cancer cells invade tissue and build blood supplies, a process central to tumor growth.
A few of those proteins already have reputations in cancer research. One flags cancer stem cells and shows up in breast and esophageal cancer patients with worse outcomes. Another helps blood vessels stick together and has been tied to cancer spreading through the body. A third helps the immune system spot and kill cancer cells, and it dropped after fire exposure here; researchers say that could hint at a temporary dip in cancer surveillance, though the study didn’t measure whether immune defenses were actually weaker.
A handful of other proteins that help hold cells together structurally also rose after fire exposure, and breakdown of that support has been linked to cancer spreading in several tumor types. A computer analysis showed many of these proteins connect to each other, suggesting they may respond to smoke as a group. None of this means firefighters develop cancer after a single call; these are early signals worth tracking, not a diagnosis.
Urine’s Kidney Filtering Explains Its Edge Over Blood
Part of why urine picked up so many more signals than blood comes down to how the body filters itself: blood contains proteins across an enormous range of concentrations, and a small number of abundant ones dominate the sample, making subtler shifts harder to detect. Urine, cleared through the kidneys, reflects a broader snapshot of what the body is processing and eliminating, making it especially sensitive to short-lived disruptions from acute exposures like fire smoke.
That gap has real consequences for occupational health testing going forward. NFPA 1582, the main national health standard for firefighter medical monitoring, calls for annual urine and blood testing but focuses largely on traditional chemistry markers rather than protein-level signals. Compliance is also voluntary and often limited outside large urban departments; volunteer firefighters, a substantial share of the U.S. fire service, frequently lack the same resources as career departments. Researchers argue that adding urine protein tracking to existing health programs could help catch cancer-related biological changes that current screening methods miss, particularly if samples are collected within 24 hours of fire suppression.
Firefighting is already known to carry serious cancer risks built up over a career. This study adds a molecular starting point: measurable signals in blood and urine showing where those risks may begin taking shape. “The body’s proteins react almost immediately,” said lead researcher Jooyeon Hwang in a statement, adding that next steps include larger studies and hydration protocols to help clear toxins after a fire.
Disclaimer: This article summarizes findings from a peer-reviewed scientific study for general informational purposes. It is not medical advice. The proteins discussed are exploratory research findings, not diagnostic tools, and no individual should interpret this article as an assessment of their personal cancer risk. Anyone with health concerns related to occupational exposure should consult a physician.
Paper Notes
Limitations
Researchers acknowledged several significant limitations. The sample size was small, and the study included only a single post-fire sampling point, which prevents any conclusions about how protein changes evolve or persist over time. Detailed information about protective equipment use, including whether and when firefighters removed their breathing apparatus during or after fire suppression, was not collected. This means the study could not assess how equipment practices influenced protein changes. Researchers also noted that the sample size was too small to adequately account for those variables. Perhaps most importantly, the biological functions of the identified proteins were not experimentally validated in this study. As the authors stated directly in the paper, “the biological and clinical significance of these findings within the present context remains speculative and requires further investigation.” No causal link between fire-smoke protein changes and actual cancer development can be drawn from this data alone.
Funding and Disclosures
This work was supported in part by the Oklahoma Shared Clinical and Translational Resources (NIGMS U54GM104938) and an Institutional Research Grant from the American Cancer Society (134128-IRG-19-142-01). Lead author Jooyeon Hwang was partially supported by the National Institute for Occupational Safety and Health (NIOSH K01OH011891) and the Southwest Center for Occupational and Environmental Health (NIOSH T42OH008421). Acknowledgment was also made of initial funding support from the OU VPRP Office for establishing the Proteomics Core Facility. The authors declared no competing financial interests.
Publication Details
Paper Title: Fire-Smoke Induced Protein Alterations in Firefighters’ Body Fluids Identify Prognostic Pan-cancer Biomarkers | Authors: Jooyeon Hwang, Zongkai Peng, Amit Singh, Chao Xu, Robert J. Agnew, Xin Xu, Zhibo Yang, and Nagib Ahsan | Journal: Environment & Health (published by ACS) | DOI: https://doi.org/10.1021/envhealth.6c00062 | Mass spectrometry data files from this study are available in the public repository MassIVE under accessions MSV000099825 and MSV000099824.
