Urinary mutagenicity and oxidative status of wildland firefighters working at prescribed burns in a Midwestern US forest

Do firefighters constitute a high-risk population for genotoxicity (DNA damage)? A systematic review

Firefighters regularly undertake high-risk operations in diverse environments, exposing them to extreme temperatures and hazardous pollutants resulting from combustion. For this reason, this systematic review aims to evaluate the potential genotoxicity associated with occupational exposure specific to firefighters. Methodologically, the review included 12 studies assessing genetic damage in firefighters. A thorough quality assessment was performed to account for potential confounding factors, and almost all studies were deemed as either strong or moderate (except for one), ensuring the reliability of the key findings. Likewise, more than half of the articles reviewed (7 out of 12) reported elevated levels of genotoxicity in firefighters, as evidenced by various assays employed in the studies. Taken together, the findings highlight the critical need for implementing biomonitoring strategies for early detection of genotoxicity among firefighters, emphasizing the necessity for further research in this occupational context.

Urinary mutagenicity and bladder cancer risk in northern New England

The etiology of bladder cancer among never smokers without occupational or environmental exposure to established urothelial carcinogens remains unclear. Urinary mutagenicity is an integrative measure that reflects recent exposure to genotoxic agents. Here, we investigated its potential association with bladder cancer in rural northern New England. We analyzed 156 bladder cancer cases and 247 cancer-free controls from a large population-based case-control study conducted in Maine, New Hampshire, and Vermont. Overnight urine samples were deconjugated enzymatically and the extracted organics were assessed for mutagenicity using the plate-incorporation Ames assay with the Salmonella frameshift strain YG1041 + S9. Logistic regression was used to estimate the odds ratios (OR) and 95% confidence intervals (CI) of bladder cancer in relation to having mutagenic versus nonmutagenic urine, adjusted for age, sex, and state, and stratified by smoking status (never, former, and current). We found evidence for an association between having mutagenic urine and increased bladder cancer risk among never smokers (OR = 3.8, 95% CI: 1.3-11.2) but not among former or current smokers. Risk could not be estimated among current smokers because nearly all cases and controls had mutagenic urine. Urinary mutagenicity among never-smoking controls could not be explained by recent exposure to established occupational and environmental mutagenic bladder carcinogens evaluated in our study. Our findings suggest that among never smokers, urinary mutagenicity potentially reflects genotoxic exposure profiles relevant to bladder carcinogenesis. Future studies are needed to replicate our findings and identify compounds and their sources that influence bladder cancer risk.

Effectiveness of dermal cleaning interventions for reducing firefighters' exposures to PAHs and genotoxins

Firefighters are exposed to carcinogenic and mutagenic combustion emissions, including polycyclic aromatic hydrocarbons (PAHs). Fire service and firefighter cancer advocacy groups recommend skin cleaning using wipes or washing with detergent and water after exposure to smoke, although these strategies have not been proven to reduce exposures to harmful combustion products such as PAHs. This study assessed dermal decontamination methods to reduce PAH exposures by firefighters participating in live fire training scenarios. Study participants (n = 88) were randomly assigned to an intervention group (i.e., two types of commercial skin wipes, detergent and water, or a control group who did not use any skin decontamination). PAHs were measured in personal air (during the fire) and dermal wipe samples (before and after fire suppression and after dermal decontamination). PAH metabolites and mutagenicity were measured in urine samples before and after fire suppression. Airborne PAH concentrations during the fire ranged between 200 and 3,970 μg/m³ (mean = 759 μg/m³, SD = 685 μg/m³). Firefighters had higher total PAHs and high-molecular-weight PAHs on their skin after the fire compared to before (1.3- and 2.2-fold, respectively, p < 0.01). Urinary PAH metabolites increased significantly following exposure to the training fires by 1.7 to 2.2-fold (depending on the metabolite, p < 0.001). Urinary mutagenicity did not differ significantly between pre- and post-fire for any of the decontamination methods. Detergent and water was the only intervention that removed a significant amount of total PAHs from the skin (0.72 ng/cm² preintervention vs. 0.38 ng/cm² postintervention, p < 0.01). However, fold changes in urinary PAH metabolites (i.e., pre- vs. post-exposure levels) did not differ among any of the dermal decontamination methods or the control group. These data suggest that despite on-site attempts to remove PAHs from firefighters' skin, the examined interventions did not reduce the internal dose of PAHs. Future work should investigate preventing initial exposure using other interventions, such as improved personal protective equipment.

The Effect of Fire Smoke Exposure on Firefighters' Lung Function: A Meta-Analysis

Firefighters are exposed to a range of harmful substances during firefighting. Exposure to fire smoke has been associated with a decrease in their lung function. However, the cause-effect relationship between those two factors is not yet demonstrated. This meta-analysis aimed to evaluate the potential associations between firefighters' occupational exposure and their lung function deterioration. Studies were identified from PubMed, Web of Science, Scopus and Science Direct databases (August 1990-March 2021). The studies were included when reporting the lung function values of Forced Expiratory Volume in 1 s (FEV1) or Forced Vital Capacity (FVC). The meta-analyses were performed using the generic inverse variance in R software with a random-effects model. Subgroup analysis was used to determine if the lung function was influenced by a potential study effect or by the participants' characteristics. A total of 5562 participants from 24 studies were included. No significant difference was found between firefighters' predicted FEV1 from wildland, 97.64% (95% CI: 91.45-103.82%; I2 = 99%), and urban fires, 99.71% (95% CI: 96.75-102.67%; I2 = 98%). Similar results were found for the predicted FVC. Nevertheless, the mean values of firefighters' predicted lung function varied significantly among studies, suggesting many confounders, such as trials' design, statistical methods, methodologies applied, firefighters' daily exposure and career length, hindering an appropriate comparison between the studies.

Unveiling Urinary Mutagenicity by the Ames Test for Occupational Risk Assessment: A Systematic Review

Occupational exposure may involve a variety of toxic compounds. A mutagenicity analysis using the Ames test can provide valuable information regarding the toxicity of absorbed xenobiotics. Through a search of relevant databases, this systematic review gathers and critically discusses the published papers (excluding other types of publications) from 2001-2021 that have assessed urinary mutagenicity (Ames test with Salmonella typhimurium) in an occupational exposure context. Due to the heterogeneity of the study methods, a meta-analysis could not be conducted. The characterized occupations were firefighters, traffic policemen, bus drivers, mail carriers, coke oven and charcoal workers, chemical laboratory staff, farmers, pharmacy workers, and professionals from several other industrial sectors. The genetically modified bacterial strains (histidine dependent) TA98, TA100, YG1041, YG1021, YG1024 and YG1042 have been used for the health risk assessment of individual (e.g., polycyclic aromatic hydrocarbons) and mixtures of compounds (e.g., diesel engine exhaust, fire smoke, industrial fumes/dyes) in different contexts. Although comparison of the data between studies is challenging, urinary mutagenicity can be very informative of possible associations between work-related exposure and the respective mutagenic potential. Careful interpretation of results and their direct use for occupational health risk assessment are crucial and yet complex; the use of several strains is highly recommended since individual and/or synergistic effects of complex exposure to xenobiotics can be overlooked. Future studies should improve the methods used to reach a standardized protocol for specific occupational environments to strengthen the applicability of the urinary mutagenicity assay and reduce inter- and intra-individual variability and exposure source confounders.

Mutagenicity and carcinogenicity of combustion emissions are impacted more by combustor technology than by fuel composition: A brief review

Studies during the past 50 years have characterized the carcinogenicity and mutagenicity of extractable organic material (EOM) of particulate matter (PM) in ambient air and from combustion emissions. We have summarized conclusions from these studies and present data supporting those conclusions for 50 combustion emissions, including carcinogenic potencies on mouse skin (papillomas/mouse/mg EOM), mutagenic potencies (revertants/μg EOM) in the Salmonella (Ames) mutagenicity assay, and mutagenicity emission factors (revertants/kg fuel or revertants/MJthermal ) in Salmonella. Mutagenic potencies of EOM from PM in ambient air and combustion emissions span 1-2 orders of magnitude, respectively. In contrast, the revertants/m3 span >5 orders of magnitude due to variable PM concentrations in ambient air. Carcinogenic potencies of EOM from combustion emissions on mouse skin and EOM-associated human lung cancer risk from those emissions both span ~3 orders of magnitude and are highly associated. The ubiquitous presence of polycyclic aromatic hydrocarbons (PAHs), nitroarenes, and aromatic amines results in mutagenic and carcinogenic potencies of PM that span only 1-3 orders of magnitude; most PM induces primarily G to T mutations. Mutagenicity emission factors of combustion emissions span 3-5 orders of magnitude and correlate with PAH emission factors (r > 0.9). Mutagenicity emission factors were largely a function of how material was burned (highly efficient modern combustors versus open burning) rather than what materials were burned. Combustion systems that minimize kinetic and mass-transfer limitations and promote complete oxidation also minimize the mutagenicity of their emissions. This fundamental engineering principle can inform environmental and public health assessments of combustion emissions.

Elevated urinary mutagenicity among those exposed to bituminous coal combustion emissions or diesel engine exhaust

Urinary mutagenicity reflects systemic exposure to complex mixtures of genotoxic/carcinogenic agents and is linked to tumor development. Coal combustion emissions (CCE) and diesel engine exhaust (DEE) are associated with cancers of the lung and other sites, but their influence on urinary mutagenicity is unclear. We investigated associations between exposure to CCE or DEE and urinary mutagenicity. In two separate cross-sectional studies of nonsmokers, organic extracts of urine were evaluated for mutagenicity levels using strain YG1041 in the Salmonella (Ames) mutagenicity assay. First, we compared levels among 10 female bituminous (smoky) coal users from Laibin, Xuanwei, China, and 10 female anthracite (smokeless) coal users. We estimated exposure-response relationships using indoor air concentrations of two carcinogens in CCE relevant to lung cancer, 5-methylchrysene (5MC), and benzo[a]pyrene (B[a]P). Second, we compared levels among 20 highly exposed male diesel factory workers and 15 unexposed male controls; we evaluated exposure-response relationships using elemental carbon (EC) as a DEE-surrogate. Age-adjusted linear regression was used to estimate associations. Laibin smoky coal users had significantly higher average urinary mutagenicity levels compared to smokeless coal users (28.4 ± 14.0 SD vs. 0.9 ± 2.8 SD rev/ml-eq, p = 2 × 10-5 ) and a significant exposure-response relationship with 5MC (p = 7 × 10-4 ). DEE-exposed workers had significantly higher urinary mutagenicity levels compared to unexposed controls (13.0 ± 10.1 SD vs. 5.6 ± 4.4 SD rev/ml-eq, p = .02) and a significant exposure-response relationship with EC (p-trend = 2 × 10-3 ). Exposure to CCE and DEE is associated with urinary mutagenicity, suggesting systemic exposure to mutagens, potentially contributing to cancer risk and development at various sites.