metabolomics

2025

1. IJHEH

   Differential Metabolic Profile by Training Fire Exposure in Female Firefighters

   Tuo Liu, James Hollister, Krystal J. Kern, and 15 more authors

   International Journal of Hygiene and Environmental Health, 2025

   Abs DOI

   Background: Women firefighters face serious health risks including elevated risk for cancer and reproductive conditions, although underlying metabolic mechanism(s) are not fully understood. Objectives: This study aimed to identify urinary metabolites and metabolic functions associated with training fire exposure among women municipal firefighters. Methods: High-resolution metabolomics (HRM) was applied to urine sample collected at baseline and after live-fire burn room/tower or flashover training fire exposure from women firefighters in the Fire Fighter Cancer Cohort Study (FFCCS). To identify differentially expressed metabolites (DEMs), differential analysis was performed using linear mixed-effects models adjusting for demographic confounders including age, socioeconomic factors, cancer history, dietary and medication behaviors, with false discovery rate adjustment. Functional enrichment analysis (FEA) was carried out using metabolite-set enrichment analysis (MSEA) from MetaboAnalyst to identify enriched metabolic processes. A secondary stratified analysis was carried out to investigate the effect of training fire type on metabolome after fire exposure using a linear regression model while adjusting for covariates. Results: One hundred women firefighters participated, resulting in a total of 200 urine samples (100 baseline, 100 postfire). The 200 samples underwent HRM analysis in four separation-ionization modes including HILIC(+), HILIC(-), C18(+), and C18(-), annotating against an in-house library of  1200 standards. We identified 200, 300, 280, and 306 metabolites and 10, 9, 23, and 19 post-training fire DEMs from the four modes, respectively. The FEA process identified that glycerophospholipid metabolism was significantly enriched at a p-value 0.05 level. Stratified analysis identified a total of 17 DEMs by fire type and increased relative ion intensities across all DEMs during burn room/tower fires compared to flashover fires. Conclusion: Women firefighters exposed to training fires exhibited a set of metabolic changes, particularly related to cellular damage from oxidative stress. These observations suggest a potential pathway for chronic inflammation with long-term fire exposure, which may help explain the higher prevalence of certain health conditions observed in women firefighters. Increased intensity DEMs were found following burn room/tower as compared with flashover fires.

2. EnvHealth

   Evaluating Urine Metabolic Profiles with Wildland- Urban-Interface (WUI) Fire Exposure: A Comparison with Municipal Structure Fires (MSF)

   Tuo Liu, Melissa A. Furlong, Shawn C. Beitel, and 5 more authors

   Environmental Health, 2025

   Abs DOI

   Firefighters have frequent exposure to carcinogens and an increased risk of cancer. Wildland-urban interface (WUI) fires, which involve both structures and undeveloped wildland fuels, pose unique challenges to the health of firefighters. However, the extent of health risks associated with these fires remains underexplored. This study aims to identify altered urine metabolites and metabolic processes among male firefighters that were associated with WUI fires as compared with municipal structure fires (MSF). Untargeted metabolomic profiling was applied to pre-exposure (baseline) and postfire urine samples collected from firefighters responding to WUI and MSF exposure. Differential analysis was conducted by fitting linear mixed effects regression models on preprocessed ion intensity and exposure status while adjusting for demographic covariates. Differential metabolites by post-exposure status were identified using a false discovery rate (FDR) threshold of <0.05. Enrichment analysis was performed to identify pathways that were significantly perturbed at a Bonferroni adjusted p-value <0.05 level. Eighty-five firefighters contributed paired baseline and post-fire samples from WUI events, and 98 firefighters contributed paired baseline and post-fire samples from MSF events. We performed metabolic profiling on baseline and postfire urine samples from WUI and structure fires using four modes: HILIC(-), HILIC(+), C18(-), and C18(+) and identified metabolites against an in-house library. We identified 244, 297, 320, and 266 level 1 metabolites from the four respective modes. In the statistical analysis, the main model identified a total of 176 differential metabolites from WUI fires. For MSF, the model identified a total of 652 differential metabolites from the four respective modes. Most metabolites with significant changes after a WUI fire also changed significantly after an MSF event. Two pathways were significantly enriched after WUI fires, while seven pathways were significantly enriched after MSF exposure and two pathways overlapped between the two types of fires. Fire exposure induces numerous metabolic perturbations in firefighters that may partially explain their elevated cancer risks. Although individual metabolites changed in a similar fashion across both WUI and MSF, structure fires were associated with an increased number of metabolite changes and some of the altered pathways differed between exposures to WUI fires vs. MSF. These results suggest that exposures to WUI fires and MSF present both common and unique cancer risks for firefighters.

3. Metabolomics

   Differential metabolic profiles by Hispanic ethnicity among male Tucson firefighters

   Tuo Liu, Melissa A. Furlong, Justin M Snider, and 10 more authors

   Metabolomics, 2025

   Abs DOI

   Introduction Firefighters face regular exposure to known and probable human carcinogens, such as polycyclic aromatic hydrocarbons (PAHs), benzene, and formaldehyde, leading to an increased risk of various cancers compared to the general population. Hispanic and black firefighters are at increased risk of additional cancers not elevated in non-Hispanic white firefighters, yet biological pathways underlying these differences are unknown. Objectives The study objectives were to evaluate differences in the urinary metabolome between Hispanic and non-Hispanic firefighters, pre-and post-fireground exposure. Methods To investigate the metabolic patterns, we employed a comprehensive metabolomics pipeline that leveraged liquid chromatography coupled with high-resolution mass spectrometry. We applied linear mixed effects regression to identify the differential metabolites at an FDR < 0.05 among 19 Hispanic and 81 non-Hispanic firefighters. We also performed overrepresentation analysis using Mummichog to identify enriched pathways at FDR < 0.05. Results Out of 175 features in HILIC(−) mode and 1847 features in RP(+) mode, we found 26 and 276 differential urinary features, respectively, when comparing Hispanic and non-Hispanic firefighters. We noted pathway enrichment in tryptophan and galactose metabolism. However, post-exposure, we did not observe differences in the metabolomic response by ethnicity despite differing fireground exposures. Conclusion Dysregulation in the tryptophan and galactose pathway is an important contributor to cancer risks and may explain the increased cancer risk among Hispanic firefighters. Supplementary Information The online version contains supplementary material available at 10.1007/s11306-024-02198-9.

2023

1. SciRep

   Evaluating changes in firefighter urinary metabolomes after structural fires: an untargeted, high resolution approach

   Melissa A Furlong, Tuo Liu, Justin M Snider, and 12 more authors

   Scientific Reports, 2023

   Abs DOI

   Firefighters have elevated rates of urinary tract cancers and other adverse health outcomes, which may be attributable to environmental occupational exposures. Untargeted metabolomics was applied to characterize this suite of environmental exposures and biological changes in response to occupational firefighting. 200 urine samples from 100 firefighters collected at baseline and two to four hours post-fire were analyzed using untargeted liquid-chromatography and high-resolution mass spectrometry. Changes in metabolite abundance after a fire were estimated with fixed effects linear regression, with false discovery rate (FDR) adjustment. Partial least squares discriminant analysis (PLS-DA) was also used, and variable important projection (VIP) scores were extracted. Systemic changes were evaluated using pathway enrichment for highly discriminating metabolites. Metabolome-wide-association-study (MWAS) identified 268 metabolites associated with firefighting activity at FDR q < 0.05. Of these, 20 were annotated with high confidence, including the amino acids taurine, proline, and betaine; the indoles kynurenic acid and indole-3-acetic acid; the known uremic toxins trimethylamine n-oxide and hippuric acid; and the hormone 7a-hydroxytestosterone. Partial least squares discriminant analysis (PLS-DA) additionally implicated choline, cortisol, and other hormones. Significant pathways included metabolism of urea cycle/amino group, alanine and aspartate, aspartate and asparagine, vitamin b3 (nicotinate and nicotinamide), and arginine and proline. Firefighters show a broad metabolic response to fires, including altered excretion of indole compounds and uremic toxins. Implicated pathways and features, particularly uremic toxins, may be important regulators of firefighter’s increased risk for urinary tract cancers.