Wildland firefighter smoke exposure and risk of lung cancer and cardiovascular disease mortality

Occupational exposure to wildland firefighting and its effects on systemic DNA damage

BACKGROUND

Portugal is among the European Union countries more devastated by forest fires. Wildland firefighters are at the forefront of this battle, facing exposure to a wide range of harmful pollutants. Epidemiological studies have highlighted a potential link between occupational firefighting exposure and several diseases, including cancer. To date, very few studies have explored the biological mechanisms associated with such exposure. The present longitudinal study aims to assess changes in early effect biomarkers following wildland firefighters' occupational exposure to a real wildfire event.

METHODS

Paired blood samples from 59 healthy Portuguese wildland firefighters were collected at two different time points: before wildfire season and after a fire event during wildfire season. Sociodemographic variables (e.g., age, sex) and work-related factors (e.g., years of service) were assessed via a self-reported questionnaire. Levels of early effect biomarkers, such as primary DNA damage and oxidative DNA damage (oxidised purines) were assessed via comet assay. DNA double-strand breaks (DSBs) were evaluated by phosphorylated H2AX (γH2AX). Moreover, hydroxylated polycyclic aromatic hydrocarbon metabolites (OHPAHs) and metal(loid)s were quantified in urine samples. The influence of urinary OHPAHs, urinary metal(loid)s, and other exposure-related factors (e.g., firefighting duration) on changes (Δ) in early effect biomarkers (post-vs. baseline levels) was investigated.

RESULTS

Firefighting activities led to a significant increase in both primary DNA damage and oxidative DNA damage by 22 % (95 % CI: 1.11-1.35; p < 0.05) and 23 % (95 % CI: 1.04-1.45; p < 0.05), respectively. Results from linear regression revealed that per each unit increase of urinary 2-hydroxyfluorene (2-OHFlu) (μmol/mol creatinine), the risk of ⧍ oxidative DNA damage increased by 20 % [FR: 1.20 (1.09-1.32); p < 0.01]. Additionally, each unit increase in urinary cesium (Cs) (μg/L) resulted in a significant 4 % increase in Δ primary DNA damage [FR: 1.04 (1.01-1.06); p < 0.05] and a 3 % increase in Δ oxidative DNA damage [FR: 1.03 (1.01-1.05); p < 0.05]. Post-exposure levels of γH2AX were significantly correlated with urinary 2-OHFlu levels assessed after firefighting (r = 0.30; p < 0.05). Furthermore, exposure duration and reported breathing difficulties during firefighting were significantly associated with increased levels of primary DNA damage.

CONCLUSION

Results obtained provide insights into the potential human health effects of wildland firefighting occupational exposure at the genetic and molecular levels, offering new and important mechanistic data. These findings are crucial for implementing health and safety measures, recommendations, and best practices to mitigate occupational risks and protect the health of wildland firefighters.

Smoke Exposure and Respirator Use Among Wildland Firefighters: A Narrative Review

Climate change contributes to warm, dry conditions, which leads to longer and more active fire seasons. Wildland firefighters work long hours in smoky conditions without regulations requiring respiratory protection. Wildfire smoke has many toxic components, including high levels of fine particulate matter (PM2.5). Regular monitoring for short- and long-term health outcomes in wildland firefighter populations is uncommon. However, extrapolating from knowledge about the individual components of smoke, it is likely that the firefighters' health is negatively affected. Firefighters are routinely exposed to dangerous levels of smoke, which may lead to both acute and chronic health consequences. Current guidelines from Occupational Safety and Health Administration (OSHA), the U.S. Forest Service (USFS), and the Interagency Standards for Fire and Fire Aviation Operations do not recommend respirator use for wildland firefighters. The methodologies used to quantify exposure and harm likely underestimate actual risks. Although there are no respirators that can filter all known harmful components of wildfire smoke, this review examines the potential benefit of respirator use by reducing some of the most harmful components of the smoke. Smoke exposure among wildland firefighters needs to be further characterized and quantified. Regulations should be reassessed to accurately reflect the exposure and potential harm that firefighters face. This narrative review gathers information from peer-reviewed scientific literature, government publications, news articles, and personal conversations with both public- and private-sector professionals. The objectives are to describe the likely health effects of wildland firefighting, evaluate the evidence behind current respiratory protection guidelines, and propose potential solutions.

Geographic patterns in wildland fire exposures and county-level lung cancer mortality in the United States

BACKGROUND

Emissions from wildfire plumes are composed of modified biomass combustion by-products, including carcinogens. However, studies of the association between wildland fires (WF; includes wildfires, prescribed burns, and resource management fires) exposure and lung cancer are scant. We evaluated geographic patterns in these exposures and their association with lung cancer mortality (LCM) rates across the conterminous United States (US).

METHODS

We extracted data from the Monitoring Trends in Burn Severity program (1997-2003) and derived county-level exposure metrics: WF density by area, WF density by population, the ratio between total burned land area and county area, and the ratio between total burned land area by population. We obtained sex-specific, county-level LCM rates for 2016-2020 from the National Center for Health Statistics. Counties with fewer than 10 cases were suppressed. To account for cigarette smoking, we first modeled residual values from a Poisson regression between cigarette smoking prevalence and sex-specific, age-adjusted LCM rates. We then used Lee's L statistic for bivariate spatial association to identify counties with statistically significant (p < 0.05) associations between WF exposures and these residuals. In a sensitivity analysis, we applied a false discovery rate correction to adjust for multiple comparisons.

RESULTS

We observed geographic variation in bivariate associations between large WFs and subsequent LCM rates across US counties while accounting for ever cigarette smoking prevalence. There were positive (high WF exposures and high LCM rate) clusters for males and females in counties within the mid-Appalachian region and Florida, and modest differences across WF metrics in the cluster patterns were observed across the Western US and Central regions. The most positive clusters were seen between WF density by area and LCM rates among women (n = 82 counties) and a similar geographic pattern among men (n = 75 counties). Similar patterns were observed for males and females in the western US, with clusters of high WF exposures and low LCM rates. After adjusting for multiple comparisons, a positive cluster pattern among both sexes persisted in Kentucky and Florida with area-based exposure metrics.

DISCUSSION

Our analysis identified counties outside the western US with wildfires associated with lung cancer mortality. Studies with individual-level exposure-response assessments are needed to evaluate this relationship further.

Particulate matter air pollution as a cause of lung cancer: epidemiological and experimental evidence

Air pollution has a significant global impact on human health. Epidemiological evidence strongly suggests that airborne particulate matter (PM), the dust components of polluted air, is associated with increased incidence and mortality of lung cancer. PM2.5 (PM less than 2.5 µm) from various sources carries different toxic substances, such as sulfates, organic compounds, polycyclic aromatic hydrocarbons, and heavy metals, which are considered major carcinogens that increase lung cancer risk. The incidence and mortality of lung cancer caused by PM2.5 exposure may be due to significant geographical differences, and can be influenced by various factors, including local sources of air pollution, socioeconomic conditions, and public health measures. This review aims to provide comprehensive insights into the health implications of air pollution and to inform strategies for lung cancer prevention, by summarising the relationship between exposure to PM2.5 and lung cancer development. We explore the different sources of PM2.5 and relevant carcinogenic mechanisms in the context of epidemiological studies on the development of lung cancer from various geographical regions worldwide.

Air quality, respiratory health and performance in athletes: a summary of the IOC consensus subgroup narrative review on 'Acute Respiratory Illness in Athletes'

With the WHO stating that nearly 99% of the global population is exposed to air pollution levels that increase the risk of chronic diseases, the question of exercising in polluted environments is relevant to the health of athletes. Major sporting events held under conditions of poor air quality (AQ) have highlighted the lack of answers to concerns raised by organisers and athletes about the associated health risks. This evidence-based narrative review compiles current knowledge and identifies gaps regarding the relationship between AQ and sport. It is a summary of a more comprehensive report prepared for the International Olympic Committee (IOC) Medical and Scientific Commission. This article discusses the various sources of air pollutants encountered during exercise, summarises current AQ guidelines and provides insights into AQ conditions during the Paris 2024 Olympic and Paralympic Games (OPG) as well as in Los Angeles over the past four summers, in preparation for the 2028 OPG. It also summarises the effects of air pollution on the respiratory health and performance of athletes, while proposing mitigation strategies, with a particular emphasis on AQ education.

Pollution and toxicity of heavy metals in wildfires-affected soil and surface water: A review and meta-analysis

Wildfires, both natural and man-made, release and mobilize hazardous substances such as heavy metal(loids) (HM), which are known carcinogens. Following intense rainfall events, HM bound to soil organic matter are transported from the soil to surface water, resulting in water quality degradation. This study reviews the pollution status of HM in wildfire-affected soil and surface water, as well as their toxic effects on aquatic organisms and humans. The rate of HM release during wildfires depends on factors such as the type of tree burned and fire severity. The mobility of HM from soil to surface water is influenced by soil pH, organic matter content, rainfall intensity, and duration. The risk priority number (RPN) analysis indicates that both wildfire-affected soil and surface water require remediation to address HM contamination. HM concentrations in both soil and surface water decrease over time due to soil erosion, wind, storm events, and the depletion of burnt residues. The greatest percentage changes in HM concentrations in burned soils compared to unburned soils were observed for vanadium (340%), nickel (260%), and arsenic (110%). In surface water, the highest increases were seen for iron (740%), vanadium (530%), and aluminium (510%). Wildfire-affected water has been shown to cause toxic effects in aquatic organisms, including DNA damage, oxidative stress, and lipid peroxidation. The consumption of HM-contaminated water and fish poses significant health risks to humans. Therefore, post-fire monitoring of wildfire-affected areas is essential for designing treatment plants, assessing risks, and establishing maximum allowable HM concentrations in water.

Heavy metal(loid) contamination in forest fire affected soil and surface water: pollution indices and human health risk assessment

Forest fires, whether natural or anthropogenic, release and mobilize heavy metal(loids) (HM). Following intense rainfall events, soil-bound HM are transported from soil to surface water through surface runoff, leading to water quality deterioration. Pollution and ecological risk indices are effective tools for assessing HM contamination. Most forest fire-affected soils and surface water exhibited a degree of contamination greater than 3 and 8 (high and moderate pollution), with associated high and extremely high ecological risks (165 and 2389, respectively). Pollution indices revealed that soils were highly contaminated with Ni, Cu, Cr, and Pb, while Ni, Cu, Hg, Cd, and As posed significant ecological risks. Surface water was heavily contaminated with Pb, Mn, Al, and Fe, with Ni and V contributing to extremely high ecological risks. This study highlights that trace HM also requires substantial removal efforts to make water potable, with removal efficiencies needed for Sb (94.49%), Be (85.83%), Ba (70.75%), V (68.19%), and Se (65.51%). Fire-affected surface water poses an elevated cancer risk to both children (0.18 and 4.5 × 10-3) and adults (0.39 and 1.53 × 10-3) through oral and dermal exposure, respectively. Children are more vulnerable to dermal cancer and noncancer risks compared to adults. Low-cost treatment methods, such as the application of immobilizing agents combined with compost, straw mulching, and seeding, can be implemented to control soil erosion in forest areas, thereby reducing the transport of soil-bound HM to surface water. These findings can aid government agencies in developing new soil and water quality standards and implementing effective treatment measures.

[Wildfires and their respiratory impact]

INTRODUCTION

Largely due to climate change, wildland fires are currently increasing in extent and frequency. While particles from fire smoke exhibit higher toxicity, those identified in wildland urban interface (WUI) areas, which are exacerbated by household and vehicle emissions, are even more toxic.

STATE OF THE ART

This review article is based on English-language papers published by peer-reviewed journals. Since a previous review article was published in 2018, only papers since 2017 have been selected. The respiratory impacts of wildfires in the general population include irritative symptoms, exacerbation of chronic respiratory diseases (asthma, rhino-sinusitis, COPD…) and excess short and probably long-term mortality. Among firefighters, the short-term impact of wildfires on respiratory function has yet to be clearly established. Asthma prevalence, asthma exacerbation rates and chronic obstructive pulmonary disease (COPD) occurrence seem to be higher than in other occupational groups. That said, the different studies have not highlighted excess mortality. As regards cancer, while mesothelioma incidence has clearly increased, lung cancer incidence generally has not.

PERSPECTIVES

Two areas require clarification: first, short-term respiratory impact according to the characteristics of inhaled smoke; the long-term impact of exposure to particles from fire smoke.

CONCLUSION

Forest fires have become increasingly worrisome, in terms of both their negative health impact and their detrimental contribution to climate change.

Source-resolved black carbon and PM2.5 exposures during wildfires and prescribed burns

Changes in climate and land-use have significantly increased both the frequency and intensity of wildland fires globally, exacerbating the potential for hazardous impacts on human health. A better understanding of particle exposure concentrations and scenarios is crucial for developing mitigation strategies to reduce the health risks. Here, PM2.5 and black carbon (BC) concentrations were monitored during wildland fires between 2022 and 2024, in fire-prone areas in Catalonia (NE Spain), by means of personal monitors (AirBeam2 and Micro-aethalometers AE51 and MA200). Results revealed that exposures to combustion aerosols (PM2.5 and BC) were significant and comparable during wildfires and prescribed burns (mean PM2.5 during wildfires = 152 μg/m3 vs. 110-145 μg/m3 for prescribed burns). Overall, BC/PM2.5 ratios showed a large variability as a function of the monitoring scenario, indicating varying contributions from mineral aerosols to the emissions mix originating from fire management and extinction tasks. Specifically, mop-up tasks (final extinction tasks involving stirring top soil using handheld tools) were identified as a significant contributor to PM2.5 exposures, with 1-min PM2.5 peak concentrations reaching up to 1190 μg/m3. These results may be especially valuable for emissions modelling. Source apportionment of multi-wavelength BC datasets provided deeper insights into emissions and their impact on exposure profiles: line operators (who control the fire perimeter) were predominantly exposed to biomass burning smoke BCbb (61%) when compared to BC from fossil-fuel combustion (BCff = 39%), while torchers (in charge of initiating technical fires using fossil-fuel drip-torches) were predominantly exposed to BCff (77% vs. 23% BCbb). These findings highlight the value of portable monitors in the assessment of wildfire emissions and impacts on human exposure and environment. The combination of these tools, reporting data in real-time and with high time-resolution, is key to the design and implementation of effective mitigation strategies for environmental and health concerns related to wildland fires.

Determinants of Health and Performance in Wildland Firefighters: A Narrative Review

BACKGROUND/OBJECTIVES

Wildland firefighters (WFFs) are subjected to significant physical and physiological demands that expose them to substantial occupational risks, including thermal stress, prolonged physical exertion, and exposure to harmful substances. These factors not only affect their immediate performance but also have long-term implications for their health. This narrative review seeks to analyze the main factors influencing the health and performance of WFFs, with a particular focus on physical, environmental, and psychological challenges.

METHODS

A narrative review was performed, synthesizing data from diverse sources. The analysis centered on studies addressing the physiological, environmental, and psychological aspects of WFF performance. Specific topics included physical workload, exposure to environmental stressors, use of protective equipment, hydration, sleep patterns, and mental health.

RESULTS

The review highlights several critical challenges faced by WFFs, including the extreme physical demands of carrying heavy equipment during extended interventions, elevated physiological strain induced by protective gear, and significant health risks associated with smoke inhalation and dehydration. Additionally, inadequate sleep and heightened mental stress were found to impair both cognitive and physical performance. Variations in injury prevalence and patterns of chronic pain were observed, often influenced by factors such as sex, age, and professional experience.

CONCLUSION

To mitigate these risks and enhance the health and performance of WFFs, targeted interventions are essential. These include tailored physical training programs, heat acclimatization strategies, and improved resource management. Future research should aim to integrate these measures comprehensively and address existing knowledge gaps to ensure the long-term well-being of these professionals.

Health effects of repeated exposures during wildland firefighting: a data-linkage cohort study from Alberta, Canada

INTRODUCTION

Very little is known about the effects on the health of work as a wildland firefighter over repeated fire seasons. In Alberta, where the fire season runs from 1 March to 31 October, the great majority of firefighters are hired seasonally. We examined whether there was a dose-response relationship between hours of firefighting and ill-health.

METHODS

A cohort was established linking employment records from Alberta Wildfire to administrative health data and cancer records. The employment records contained information on each deployment for all firefighters with employment from 1998 to 2022. Health records had details of diagnoses recorded at all physician consultations for the same period. Cancer records included diagnostic information for all confirmed cancers in the province. Exposure indices (hours worked) were related to health outcomes, with relative risk estimated by multilevel Poisson regression, using data lagged by 10 years for cancer outcomes.

RESULTS

Of 16,816 firefighters with employment records, 12,731 were matched on name, age, and sex in health records and were living in Alberta at the end of at least one fiscal year. One in three had only been employed for one fire season with 10% employed in 10 or more years. The overall mean cumulative exposure was 795 h with 568 h of sustained attack (SA). In multivariable regression, adjusted for age, sex, and inferred First Nation origin, the risk of chronic obstructive pulmonary disease (COPD) and pneumonia increased with hours of firefighting on foot and decreased with fighting less complex fires or holding a permanent appointment. Hours of firefighting in the year of health report were protective for cardiovascular disease (CVD) and mental ill-health but the risk of injury from external causes increased with firefighting hours. The risk of COPD, pneumonia, and asthma increased with cumulative hours over multiple fire seasons of SA firefighting and decreased with cumulative hours fighting less complex fires. Risks of CVD and mental ill-health were also positively related to cumulative hours of SA. No increase in risk was found with cancer incidence (all cancers, bladder cancer, lung cancer, skin: melanoma or nonmelanoma), with exposures unlagged or lagged by 10 years.

CONCLUSION

Wildland firefighters were found to be at increased risk of lung conditions, both acutely in the year of firefighting and in subsequent years. No increased risk was found for cancer.

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.

Intra-Continental Transport of Western Wildfire Smoke Heightens Health Risks Across North America

Wildfires in North America, particularly in western states, have caused widespread environmental, economic, social, and health impacts. Smoke from these fires travels long distances, spreading pollutants and worsening the air quality across continents. Vulnerable groups, such as children, the elderly, and those with preexisting conditions, face heightened health risks, as do firefighters working in extreme conditions. Wildfire firefighters are of particular concern as they are fighting fires in extreme conditions with minimal protective equipment. This study examined wildfire smoke during July-August 2021, when intense fires in Canada and the western U.S. led to cross-continental smoke transport and caused significant impacts on the air quality across North America. Using the GEOS-Chem model, we simulated the transport and distribution of PM2.5 (particulate matter with a diameter of 2.5 μm or smaller), identifying significant carcinogenic risks for adults, children, and firefighters using dosimetry risk methodologies established by the U.S. EPA. Significant carcinogenic risks for adult, child, and firefighter populations due to exposure to PM2.5 were identified over the two-month period of evaluation. The findings emphasize the need for future studies to assess the toxic chemical mixtures in wildfire smoke and consider the risks to underrepresented communities.

Factors associated with lung cancer among firefighters: a systematic literature review

This short review addresses the pressing issue of lung cancer among firefighters, a population facing unique occupational hazards such as smoke inhalation and asbestos exposure. With lung cancer being a leading global cause of death, the study emphasizes the disproportionate burden on firefighters. Notably, wildfire smoke, containing carcinogenic elements, poses a rising significant threat to firefighters' respiratory health. Despite evidence linking firefighting to increased lung cancer risk, few studies have explored the underlying mechanisms. This study conducts a comprehensive review employing PRISMA guidelines to synthesize existing literature from 1972 to 2022. We discuss the association between age, race, and time spent fighting fires with lung cancer development. Our review also underscores the scarcity of studies investigating specific carcinogens and their role in firefighters' lung cancer risk, emphasizing the need for more targeted research. The study advocates for improved methodology, suggesting the use of individual-level exposure metrics like "fire-hours" to enhance causal inference. Despite limitations in current literature, the findings stress the urgency of understanding the intricacies of lung cancer development among firefighters and call for further research to inform preventive measures and potential screening protocols.

Epigenetic Modifications Associated With Wildland-Urban Interface (WUI) Firefighting

Wildland-urban interface (WUI) firefighting involves exposure to burning vegetation, structures, and other human-made hazards, often without respiratory protection. Response activities can last for long periods of time, spanning multiple days or weeks. Epigenetic modifications, including microRNA (miRNA) expression and DNA methylation, are responsive to toxicant exposures and are part of the development of cancers and other diseases. Epigenetic modifications have not been studied in relation to WUI fires. Firefighters (n = 99) from southern California, including 79 firefighters who responded to at least one WUI fire, provided blood samples at baseline and approximately 10 months later. We quantified the relative abundance of 800 miRNAs in blood samples using the nCounter Human v3 miRNA expression panel and blood leukocyte DNA methylation throughout the genome via the Infinium EPIC array. We used linear mixed models to compare the expression of each miRNA across time and DNA methylation at each locus, adjusting for potential confounders. In the miRNA analysis among all firefighters, 65 miRNAs were significantly different at follow-up compared to baseline at a false discovery rate of 5%. Results were similar when restricted to firefighters with a recorded WUI fire exposure during the interim period, although only 50 were significant. Expression of miRNA hsa-miR-518c-3p, a tumor suppressor, was significantly associated with WUI fire response (fold change 0.77, 95% CI = [0.69, 0.87]). In the DNA methylation analysis, no statistically significant changes over time were identified. In summary, WUI fire exposures over a wildfire season altered miRNA expression but did not substantially impact DNA methylation.

Systematic review of impacts of occupational exposure to wildfire smoke on respiratory function, symptoms, measures and diseases

BACKGROUND

Wildfire smoke contains numerous hazardous air pollutants which pose serious health risks to humans. Despite this, there has been a limited focus on the assessment of the acute physiological and longer-term respiratory effects of wildfire exposure on firefighters and other emergency workers. Therefore, we undertook a systematic review of the evidence about the respiratory impacts of occupational wildfire smoke exposure among wildfire fighters (WFF).

METHODS

Eligible studies from Medline, Embase and Scopus databases were included if they described the relationship between wildfire exposure and respiratory function, symptoms, measures and diseases amongst emergency personnel or firefighters who had responded to wildfires.

RESULTS

Twenty-six articles met the inclusion criteria. 24 out of 26 (22 out of 23 moderate/high quality) studies provided evidence of adverse respiratory effects, including reduced lung function, increased airway dysfunction and airway inflammation, upper and lower respiratory tract symptoms and increased asthma incidence related to wildfires or prescribed burns exposure among WFF and police responders. Fourteen out of 19 studies showed statistically significant declines in spirometry measures of lung function (mostly short-term studies). Two studies using complex lung function tests showed a significant effect on peripheral airway function.

DISCUSSION

This review found a convincing body of evidence that occupational exposure to wildfires or prescribed burns has both acute and possibly longer-term respiratory effects among WFFs and some other emergency personnel. Given that these events are increasing, more needs to be done to identify those most at risk and mitigate these risks.

Wildfire Smoke: Health Effects, Mechanisms, and Mitigation

Wildfires are becoming more frequent and intense on a global scale, raising concerns about their acute and long-term effects on human health. We conducted a systematic review of the current epidemiological evidence on wildfire health risks and a meta-analysis to investigate the association between wildfire smoke exposure and various health outcomes. We discovered that wildfire smoke increases the risk of premature deaths and respiratory morbidity in the general population. Meta-analysis of cause-specific mortality and morbidity revealed that wildfire smoke had the strongest associations with cardiovascular mortality (RR: 1.018, 95% CI: 1.014-1.021), asthma hospitalization (RR: 1.054, 95% CI: 1.026-1.082), and asthma emergency department visits (RR: 1.117, 95% CI: 1.035-1.204) in the general population. Subgroup analyses of age found that adults and elderly adults were more susceptible to the cardiopulmonary effects of wildfire smoke. Next, we systematically addressed the toxicological mechanisms of wildfire smoke, including direct toxicity, oxidative stress, inflammatory reactions, immune dysregulation, genotoxicity and mutations, skin allergies, inflammation, and others. We discuss wildfire smoke risk mitigation strategies including public health interventions, regulatory measures, and personal actions. We conclude by highlighting current research limitations and future directions for wildfire research, such as elucidating the complex interactions of wildfire smoke components on human health, developing personalized risk assessment tools, and improving resilience and adaptation strategies to mitigate the health effects of wildfires in changing climate.

Non-Genotoxic and Environmentally Relevant Lower Molecular Weight Polycyclic Aromatic Hydrocarbons Significantly Increase Tumorigenicity of Benzo[a]pyrene in a Lung Two-Stage Mouse Model

The World Health Organization has classified air pollution as a carcinogen, and polycyclic aromatic hydrocarbons (PAHs) are major components of air particulates of carcinogenic concern. Thus far, most studies focused on genotoxic high molecular weight PAHs; however, recent studies indicate potential carcinogenicity of the non-genotoxic lower molecular weight PAHs (LMW PAHs) that are found in indoor and outdoor air pollution as well as secondhand cigarette smoke. We hypothesize that LMW PAHs contribute to the promotion stage of cancer when combined with benzo[a]pyrene (B[a]P), a legacy PAH. We specifically determined the effects of an LMW PAH mixture containing 1-methylanthracene (1MeA), fluoranthene (Flthn), and phenanthrene (Phe) combined with B[a]P on lung tumor promotion. To test this hypothesis, we used a two-stage, initiation/promotion BALB/ByJ female lung tumor mouse model. The mice were initiated with 3-methylcholanthrene followed by exposures to B[a]P, the LMW PAH mixture, and the combination of the LMW PAH mixture plus B[a]P, all at 10 mg/kg. The LMW PAHs combined with B[a]P significantly increased the promotion and incidence of lung tumors over that of B[a]P alone. The LMW PAHs in the absence of B[a]P did not significantly promote tumors, indicating strong co-promotional activities. We further assessed the effects of these PAHs on other hallmarks of cancer, namely, bronchoalveolar lavage fluid inflammatory infiltrates, pro-inflammatory transcripts, KC protein content, and mRNA expression of the gap junction (Gja1) and epiregulin (Ereg) genes. The LMW PAHs increased the biomarkers of inflammation, decreased Gja1 expression, and increased Ereg expression, all consistent with tumor promotion. This study indicates that non-genotoxic LMW PAHs can contribute to the cancer process and warrants further studies to assess the carcinogenic risks of other LMW PAHs.

Clair JM, Warneke C, Wolfe GM, Womack C. Evolution of Reactive Organic Compounds and Their Potential Health Risk in Wildfire Smoke

Wildfires are an increasing source of emissions into the air, with health effects modulated by the abundance and toxicity of individual species. In this work, we estimate reactive organic compounds (ROC) in western U.S. wildland forest fire smoke using a combination of observations from the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) field campaign and predictions from the Community Multiscale Air Quality (CMAQ) model. Standard emission inventory methods capture 40-45% of the estimated ROC mass emitted, with estimates of primary organic aerosol particularly low (5-8×). Downwind, gas-phase species abundances in molar units reflect the production of fragmentation products such as formaldehyde and methanol. Mass-based units emphasize larger compounds, which tend to be unidentified at an individual species level, are less volatile, and are typically not measured in the gas phase. Fire emissions are estimated to total 1250 ± 60 g·C of ROC per kg·C of CO, implying as much carbon is emitted as ROC as is emitted as CO. Particulate ROC has the potential to dominate the cancer and noncancer risk of long-term exposure to inhaled smoke, and better constraining these estimates will require information on the toxicity of particulate ROC from forest fires.

Striving for Equity: Examining Health Disparities in Urologic Oncology

Health disparities in urologic oncology, particularly in prostate, bladder, kidney, and testicular cancers, significantly impact patient outcomes across different demographic groups. This narrative review aims to investigate the extent and drivers of these disparities, focusing on the influence of race, socioeconomic status, and geographic location on diagnosis, treatment, and survival outcomes. We conducted a comprehensive review of the existing literature and analyzed data from national cancer databases to identify patterns of inequity. Our findings reveal that minority populations, individuals with lower socioeconomic status, and those residing in underserved areas are less likely to receive timely and guideline-based care, leading to worse outcomes. This review underscores the urgent need for targeted interventions, including policy reforms, health system restructuring, enhanced community outreach, and increased funding for disparity-focused research, to ensure equitable access to high-quality oncologic care. Addressing these disparities is crucial for improving cancer outcomes and achieving health equity in urologic oncology.

The Emission Characteristics and Health Risks of Firefighter-Accessed Fire: A Review

The exacerbation of wildfires caused by global warming poses a significant threat to human health and environmental integrity. This review examines the particulate matter (PM) and gaseous pollutants resulting from fire incidents and their impacts on individual health, with a specific focus on the occupational hazards faced by firefighters. Of particular concern is the release of carbon-containing gases and fine particulate matter (PM2.5) from forest fires and urban conflagrations, which exceed the recommended limits and pose severe health risks. Firefighters exposed to these pollutants demonstrate an elevated risk of developing pulmonary and cardiovascular diseases and cancer compared to the general population, indicating an urgent need for enhanced protective measures and health management strategies for firefighters. Through a meticulous analysis of the current research findings, this review delineates future research directions, focusing on the composition and properties of these pollutants, the impacts of fire-emitted pollutants on human health, and the development of novel protective technologies.

Blinded by smoke: Wildfire smoke exposure and eye irritation in australian wildland firefighters

PURPOSE

Wildfire occurrence is increasing worldwide, putting firefighters and general public at increased risk of eye injuries from smoke exposure. This study explored ocular symptoms and use of protective eyewear amongst wildland firefighters in Australia.

METHODS

Australian wildland firefighters were invited to complete an online survey about the occurrence of eye irritation, use of protective eyewear and behaviours associated with occupational smoke exposure. Responses were analysed using logistic regression and qualitative inductive content analysis.

RESULTS

338 wildland firefighters completed the survey. Eye irritation was reported by 90 % of firefighters at least sometimes during work and by 70 % after work. Frequency of eye irritation was greater amongst females than males (OR 2.01, CI 1.22-3.31, p < 0.001). Protective eyewear was used often or always by 67 % of firefighters on the fireground, however 55 % had to remove their protective eyewear due to sweat, fogging or another reason. Goggles were more likely to be removed compared to sunglasses and safety glasses (OR 4.28, CI 2.75-6.68, p < 0.001). Firefighters reported that, at times smoke exposure necessitated eye closure and impaired vision on the fireground. Firefighters also reported that protective eyewear helped to reduce eye symptoms, but its consistent use on the fireground was difficult. The severity and recovery from eye symptoms varied between participants.

CONCLUSION

Australian wildland firefighters frequently experience eye irritation from smoke exposure, and this can affect operational capabilities. These findings can support the development of evidence-based strategies to help protect and aid recovery of the eye surface following smoke exposure.

Robust differential gene expression patterns in the prefrontal cortex of male mice exposed to an occupationally relevant dose of laboratory-generated wildfire smoke

Wildfires have become common global phenomena concurrent with warmer and drier climates and are now major contributors to ambient air pollution worldwide. Exposure to wildfire smoke has been classically associated with adverse cardiopulmonary health outcomes, especially in vulnerable populations. Recent work has expanded our understanding of wildfire smoke toxicology to include effects on the central nervous system and reproductive function; however, the neurotoxic profile of this toxicant remains ill-explored in an occupational context. Here, we sought to address this by using RNA sequencing to examine transcriptomic signatures in the prefrontal cortex of male mice modeling career wildland firefighter smoke exposure. We report robust changes in gene expression profiles between smoke-exposed samples and filtered air controls, evidenced by 2,862 differentially expressed genes (51.2% increased). We further characterized the functional relevance of these genes highlighting enriched pathways related to synaptic transmission, neuroplasticity, blood-brain barrier integrity, and neurotransmitter metabolism. Additionally, we identified possible contributors to these alterations through protein-protein interaction network mapping, which revealed a central node at ß-catenin and secondary hubs centered around mitochondrial oxidases, the Wnt signaling pathway, and gene expression machinery. The data reported here will serve as the foundation for future experiments aiming to characterize the phenotypic effects and mechanistic underpinnings of occupational wildfire smoke neurotoxicology.

A review of occupational exposures to carcinogens among wildland firefighters

Wildfires can negatively impact the health and well-being of wildland firefighters through a variety of exposure pathways. Many studies have measured acute health effects from occupational exposure to pollutants in wildfire smoke; however, research specifically examining cancer risks from exposure to carcinogens is limited. This review aimed to better understand cancer risk in this occupation by assessing the existing evidence of exposures and summarizing measured concentrations of carcinogens among wildland firefighters. A systematic search was conducted to identify scientific papers using the following databases: Medline(OVID), Embase(OVID), PsycINFO(OVID), Cochrane Library, CINAHL(EBSCOHost), EconLit(EBSCOHost), Scopus, Agricultural and Environmental Science Collect(ProQuest), and NIOSHTIC-2. Forty-nine papers were identified that met eligibility criteria. Across the papers, 31 carcinogens were identified and quantified using a variety of assessment methods. Papers measured particulate matter (N = 26), polycyclic aromatic hydrocarbons (N = 12), volatile organic compounds (N = 14), crystalline silica (N = 5), black carbon (N = 4), asbestos (N = 3), radionuclides (N = 7), and metals (N = 2). Most papers measured inhalation exposures through traditional air sampling methods, but a subset of exposures to polycyclic aromatic hydrocarbons (N = 8), as well as heavy metals (N = 1), were measured through urinary biomarkers and naphthalene was measured using dermal wipe samples (N = 2). Although the heterogeneity of exposure assessment methods made direct comparison of concentrations difficult, the papers provide consistent evidence that wildland firefighters are regularly exposed to carcinogens. All wildland fire personnel should continue to implement recommended mitigation strategies and support new mitigations to reduce exposure to carcinogens on the job.

Wildland Firefighter Work History and Clinical Indicators of Cardiovascular Health

OBJECTIVE

To determine the association between the occupational history as a wildland firefighter (WFF) and clinical indicators of cardiovascular health.

METHODS

Among 2862 WFFs, we evaluated associations between the number of total days assigned on fire and high-risk categories of three clinically measured cardiovascular indicators.

RESULTS

Almost one-third (32%) of WFFs had one or more clinical measures that would place them in high-risk categories for body mass index, blood pressure, and total cholesterol. WFF work history was associated with some of these measures: odds ratio (and 95% confidence interval) for highest versus lowest tertile of days on fire were 1.4 (1.2, 1.8) and 1.2 (1.0, 1.5) for high-risk categories of body mass index and cholesterol, respectively.

CONCLUSION

More frequent screening and targeted health promotion programs for WFFs are warranted to increase awareness of cardiovascular risk and prevention strategies.

Perceptions of Exposure and Mask Use in Wildland Firefighters

Wildland firefighters are exposed to airborne particulates, polycyclic aromatic hydrocarbons (PAHs), and other hazardous substances. Respiratory protection is indicated, but information is lacking on the tasks and conditions for which mask wearing should be advised. Studies to assess respiratory protection in wildland firefighters were carried out in western Canada in 2021 and 2023. Sampling pumps measured airborne exposures and urinary 1-hydroxypyrene (1-HP) was assayed to indicate PAH absorption. Participants in 2021 reported the time for which they wore the mask during each task. In 2023, the use of masks was reported, and firefighters rated the smoke intensity. In 2021, 72 firefighters were monitored over 164 shifts and, in 2023, 89 firefighters were monitored for 263 shifts. In 2021, mask wearing was highest for those engaged in initial attack and hot spotting. Urinary 1-HP at the end of rotation was highest for those reporting initial attack, working on a prescribed fire and mop-up. In 2023, firefighter ratings of smoke intensity were strongly associated with measured particulate mass and with urinary 1-HP, but masks were not worn more often when there was higher smoke intensity. The data from the literature did not provide a clear indication of high-exposure tasks. Better task/exposure information is needed for firefighters to make informed decisions about mask wearing.

Size-resolved particulate matter inside selected fire stations and preliminary evaluation of the effectiveness of washing machines in reducing its concentrations

The study aimed to determine and compare the mass concentration and size distribution of particulate matter (PM) at two Polish fire stations, one equipped with a washing machine intended for the decontamination of uniforms (FSN) and the other not equipped with this type of device (FSC), to assess the effectiveness of washing machines in reducing PM concentrations inside fire stations and estimate PM doses inhaled by firefighters while performing activities in truck bays and changing rooms during one work shift. The average PM concentrations at the FSN were 18.2-28.9 µg/m3 and 27.5-37.3 µg/m3, while at FSC they were 27.4-37.9 µg/m3 and 24.6-32.8 µg/m3 in the truck bays and changing rooms, respectively. At each measurement point, most of the PM mass (65-75%) was accumulated as fine particles. The dominance of fine particles in the total mass of PM results in high values of PM deposition coefficients (0.59-0.61) in three sections of the respiratory tract at each monitoring site. This study initially indicates the effectiveness of washing machines in reducing the concentration of fine particles and demonstrates the necessity, as well as directions for further research in this area.

Decoding Cancer Risk: Understanding Gene-Environment Interactions in Cancer Development

While lifestyle choices or behavioral patterns remain the most significant factors influencing cancer risk, environmental exposure to certain chemicals, both manufactured and natural, may also contribute to an individual's likelihood of developing cancer. This interplay of factors, coupled with an aging demographic and shifting lifestyle patterns, has led to an increasing prevalence of cancer in recent years. This study examines the environmental and behavioral factors that contribute to anomalies in the immune system and increase the risk of developing cancer. Significant environmental and occupational factors include the contamination of air and water, exposure to radiation, contact with harmful microorganisms and pathogens, and workplace exposure to carcinogens such as asbestos, certain chemicals, and industrial pollutants. Behavioral factors, such as food, physical activity, stress, substance misuse, and sleep patterns, have a substantial impact on immunological function and the likelihood of developing cancer. For example, pollutants like benzene and arsenic can disrupt immune function and raise the risk of developing cancer. Similarly, lifestyle variables such as inactivity and poor nutrition have been linked to an increased risk of cancer. Long-term stress and substance abuse can also decrease immunological responses, increasing the risk of developing cancer. The review underlines the complexities of examining gene-environment interactions, as well as the importance of using several perspectives to fully comprehend these pathways. Future investigations should emphasize improved methodology and larger sample sizes. Public health campaigns should aim to reduce human exposure to cancer-causing compounds known as carcinogens while also encouraging the adoption of healthy behaviors and habits. Tailored preventive approaches that account for individual genetic vulnerabilities have the potential to improve cancer prevention and treatment.

Long-term exposure to wildland fire smoke PM2.5 and mortality in the contiguous United States

Despite the substantial evidence on the health effects of short-term exposure to ambient fine particles (PM2.5), including increasing studies focusing on those from wildland fire smoke, the impacts of long-term wildland fire smoke PM2.5 exposure remain unclear. We investigated the association between long-term exposure to wildland fire smoke PM2.5 and non-accidental mortality and mortality from a wide range of specific causes in all 3,108 counties in the contiguous U.S., 2007-2020. Controlling for non-smoke PM2.5, air temperature, and unmeasured spatial and temporal confounders, we found a non-linear association between 12-month moving average concentration of smoke PM2.5 and monthly non-accidental mortality rate. Relative to a month with the long-term smoke PM2.5 exposure below 0.1 μg/m3, non-accidental mortality increased by 0.16-0.63 and 2.11 deaths per 100,000 people per month when the 12-month moving average of PM2.5 concentration was of 0.1-5 and 5+ μg/m3, respectively. Cardiovascular, ischemic heart disease, digestive, endocrine, diabetes, mental, and chronic kidney disease mortality were all found to be associated with long-term wildland fire smoke PM2.5 exposure. Smoke PM2.5 contributed to approximately 11,415 non-accidental deaths/year (95% CI: 6,754, 16,075) in the contiguous U.S. Higher smoke PM2.5-related increases in mortality rates were found for people aged 65 above. Positive interaction effects with extreme heat (monthly number of days with daily mean air temperature higher than the county's 90th percentile warm season air temperature) were also observed. Our study identified the detrimental effects of long-term exposure to wildland fire smoke PM2.5 on a wide range of mortality outcomes, underscoring the need for public health actions and communications that span the health risks of both short- and long-term exposure.

Repeated exposure to eucalyptus wood smoke alters pulmonary gene and metabolic profiles in male Long-Evans rats

Exposure to wildfire smoke is associated with both acute and chronic cardiopulmonary illnesses, which are of special concern for wildland firefighters who experience repeated exposure to wood smoke. It is necessary to better understand the underlying pathophysiology by which wood smoke exposure increases pulmonary disease burdens in this population. We hypothesize that wood smoke exposure produces pulmonary dysfunction, lung inflammation, and gene expression profiles associated with future pulmonary complications. Male Long-Evans rats were intermittently exposed to smoldering eucalyptus wood smoke at 2 concentrations, low (11.0 ± 1.89 mg/m3) and high (23.7 ± 0.077 mg/m3), over a 2-week period. Whole-body plethysmography was measured intermittently throughout. Lung tissue and lavage fluid were collected 24 h after the final exposure for transcriptomics and metabolomics. Increasing smoke exposure upregulated neutrophils and select cytokines in the bronchoalveolar lavage fluid. In total, 3446 genes were differentially expressed in the lungs of rats in the high smoke exposure and only 1 gene in the low smoke exposure (Cd151). Genes altered in the high smoke group reflected changes to the Eukaryotic Initiation Factor 2 stress and oxidative stress responses, which mirrored metabolomics analyses. xMWAS-integrated analysis revealed that smoke exposure significantly altered pathways associated with oxidative stress, lung morphogenesis, and tumor proliferation pathways. These results indicate that intermittent, 2-week exposure to eucalyptus wood smoke leads to transcriptomic and metabolic changes in the lung that may predict future lung disease development. Collectively, these findings provide insight into cellular signaling pathways that may contribute to the chronic pulmonary conditions observed in wildland firefighters.

Health burden of sugarcane burning on agricultural workers and nearby communities

Sugarcane is the most widely cultivated crop in the world, with equatorial developing nations performing most of this agriculture. Burning sugarcane is a common practice to facilitate harvest, producing extremely high volumes of respirable particulate matter in the process. These emissions are known to have deleterious effects on agricultural workers and nearby communities, but the extent of this exposure and potential toxicity remain poorly characterized. As the epidemicof chronic kidney disease of an unknown etiology (CKDu) and its associated mortality continue to increase along with respiratory distress, there is an urgent need to investigate the causes, determine viable interventions to mitigate disease andimprove outcomes for groups experiencing disproportionate impact. The goal of this review is to establish the state of available literature, summarize what is known in terms of human health risk, and provide recommendations for what areas should be prioritized in research.

Impact of Wildfires on Cardiovascular Health

Wildfire smoke (WFS) is a mixture of respirable particulate matter, environmental gases, and other hazardous pollutants that originate from the unplanned burning of arid vegetation during wildfires. The increasing size and frequency of recent wildfires has escalated public and occupational health concerns regarding WFS inhalation, by either individuals living nearby and downstream an active fire or wildland firefighters and other workers that face unavoidable exposure because of their profession. In this review, we first synthesize current evidence from environmental, controlled, and interventional human exposure studies, to highlight positive associations between WFS inhalation and cardiovascular morbidity and mortality. Motivated by these findings, we discuss preventative measures and suggest interventions to mitigate the cardiovascular impact of wildfires. We then review animal and cell exposure studies to call attention on the pathophysiological processes that support the deterioration of cardiovascular tissues and organs in response to WFS inhalation. Acknowledging the challenges of integrating evidence across independent sources, we contextualize laboratory-scale exposure approaches according to the biological processes that they model and offer suggestions for ensuring relevance to the human condition. Noting that wildfires are significant contributors to ambient air pollution, we compare the biological responses triggered by WFS to those of other harmful pollutants. We also review evidence for how WFS inhalation may trigger mechanisms that have been proposed as mediators of adverse cardiovascular effects upon exposure to air pollution. We finally conclude by highlighting research areas that demand further consideration. Overall, we aspire for this work to serve as a catalyst for regulatory initiatives to mitigate the adverse cardiovascular effects of WFS inhalation in the community and alleviate the occupational risk in wildland firefighters.

Distinct Prostate Cancer Survival Outcomes in Firefighters: A Population-Based Study

Introduction: Survival outcomes for prostate cancer among specific occupational groups prone to regular medical check-ups vis-à-vis the general population have been understudied. For firefighters, a demographic subject to rigorous medical evaluations, possessing above-average medical expertise, and exposed to specific carcinogens of interest, prostate cancer survival in the US has never been studied. Methods: We conducted a retrospective study, utilizing data from the Florida Cancer Data System spanning 2004 to 2014, coupled with firefighter certification records from the Florida State Fire Marshal's Office. Our study cohort consisted of 1058 prostate cancer cases among firefighters as well as prostate cases for the Florida general population (n = 150,623). We compared cause-specific survival between the two using Cox regression models adjusted for demographics and clinical characteristics, including PSA levels, Gleason scores, and treatment modalities. Results: Firefighters demonstrated a higher five-year cause-specific survival rate (96.1%, 95% CI: 94.7-97.1%) than the general population (94.2%, 95%CI: 94.1-94.3%). Overall, firefighters' diagnoses were established at younger ages (median age 63 vs. 67 in the general population), exhibited a higher proportion of localized stage cancers (84.7% vs. 81.1%), and had a greater utilization of surgery (46.4% vs. 37.6%), a treatment modality with a high success rate but potential side effects. In multivariable analysis, firefighters displayed a survival advantage for localized stage (adjusted hazard ratio [aHR] = 0.53; 95%CI: 0.34-0.82). However, for regional or distant stages, firefighters aged 65 and above exhibited a higher risk of death (aHR = 1.84; 95% CI: 1.18-2.86) than the general population. Conclusion: Firefighters experience enhanced prostate cancer survival, primarily in cases diagnosed at localized stages, likely due to increased PSA testing. Nonetheless, for regional or distant stage, survival among older firefighters' lags behind that of the general population. Further investigations are warranted to unravel factors influencing the development of aggressive disease beyond PSA and Gleason scores in this population, as well as to assess the impact of a higher rate of surgical treatment on firefighters' quality of life.

Cancer incidence trends in New York State and associations with common population-level exposures 2010-2018: an ecological study

The impact of common environmental exposures in combinations with socioeconomic and lifestyle factors on cancer development, particularly for young adults, remains understudied. Here, we leveraged environmental and cancer incidence data collected in New York State at the county level to examine the association between 31 exposures and 10 common cancers (i.e., lung and bronchus, thyroid, colorectal, kidney and renal pelvis, melanoma, non-Hodgkin lymphoma, and leukemia for both sexes; corpus uteri and female breast cancer; prostate cancer), for three age groups (25-49, 50-69, and 70-84 year-olds). For each cancer, we stratified by age group and sex, and applied regression models to examine the associations with multiple exposures simultaneously. The models included 642,013 incident cancer cases during 2010-2018 and found risk factors consistent with previous reports (e.g., smoking and physical inactivity). Models also found positive associations between ambient air pollutants (ozone and PM2.5) and prostate cancer, female breast cancer, and melanoma of the skin across multiple population strata. Additionally, the models were able to better explain the variation in cancer incidence data among 25-49 year-olds than the two older age groups. These findings support the impact of common environmental exposures on cancer development, particularly for younger age groups.

Subclinical Measures of Cardiovascular Health Among Wildland Firefighters

OBJECTIVE

The aim of the study is to compare subclinical measures of cardiovascular health among wildland firefighters (WFFs) to the US general population.

METHODS

Our cross-sectional study compared body mass index, total cholesterol, and blood pressure in 11,051 WFFs aged 17 to 64 years using Department of the Interior Medical Screening Program clinical screening examinations between 2014-2018 to National Health and Nutrition Examination Survey of 2015-2016 cycle using adjusted logistic regression analyses.

RESULTS

The logistic regression model shows significantly higher odds of hypertension and prehypertension in WFFs (2.84 times more with 95% CI: 2.28-3.53) than US general population. There were no consistent differences in body mass index or total cholesterol between the two population.

CONCLUSIONS

Hypertension and prehypertension were more prevalent in WFFs compared with the US general population, which suggests the need for actions for protecting against cardiovascular disease among WFFs.

Health Effects of Wildfire Smoke Exposure

We review current knowledge on the trends and drivers of global wildfire activity, advances in the measurement of wildfire smoke exposure, and evidence on the health effects of this exposure. We describe methodological issues in estimating the causal effects of wildfire smoke exposures on health and quantify their importance, emphasizing the role of nonlinear and lagged effects. We conduct a systematic review and meta-analysis of the health effects of wildfire smoke exposure, finding positive impacts on all-cause mortality and respiratory hospitalizations but less consistent evidence on cardiovascular morbidity. We conclude by highlighting priority areas for future research, including leveraging recently developed spatially and temporally resolved wildfire-specific ambient air pollution data to improve estimates of the health effects of wildfire smoke exposure.

Clearing the Air: Understanding the Impact of Wildfire Smoke on Asthma and COPD

Wildfires are a global natural phenomenon. In North America, wildfires have not only become more frequent, but also more severe and longer in duration, a trend ascribed to climate change combined with large fuel stores left from modern fire suppression. The intensification of wildfire activity has significant implications for planetary health and public health, as exposure to fine particulate matter (PM2.5) in wildfire smoke is linked to adverse health effects. This review focuses on respiratory morbidity from wildfire smoke exposure. Inhalation of wildfire PM2.5 causes lung injury via oxidative stress, local and systemic inflammation, airway epithelium compromise, and increased vulnerability to infection. Wildfire PM2.5 exposure results in exacerbations of pre-existing asthma and chronic obstructive pulmonary disease, with an escalation in healthcare utilization, including emergency department visits and hospitalizations. Wildfire smoke exposure may be associated with asthma onset, long-term impairment of lung function, and increased all-cause mortality. Children, older adults, occupationally-exposed groups, and possibly women are the most at risk from wildfire smoke. Future research is needed to clarify best practices for risk mitigation and wildfire management.

Firefighters' personal exposure to gaseous PAHs during controlled forest fires: A case study with estimation of respiratory health risks and in vitro toxicity

Firefighters are daily exposed to adverse health-hazardous pollutants. Polycyclic aromatic hydrocarbons (PAHs), well known endocrine disruptors with carcinogenic, mutagenic, and teratogenic properties, are among the most relevant pollutants. The characterization of firefighters' occupational exposure to airborne PAHs remains limited; information is scarce for European firefighters. Also, the in vitro assessment of firefighters' respiratory health risks is inexistent. To reply to these scientific gaps, this work characterizes the levels of gaseous PAH in firefighters' personal air during regular working activities at controlled forest fires and at fire stations (control group). Breathable levels were 2.2-26.7 times higher during fire events than in the control group (2.63-32.63 μg/m3versus 1.22 μg/m3, p < 0.001); the available occupational guidelines (100 and 200 μg/m3 defined by the US National Institute for Occupational Safety and Health and the North American Occupational Safety and Health Administration, respectively) were not exceeded. Concentrations of (possible/probable) carcinogenic PAHs were 1.9-15.3 times superior during firefighting (p < 0.001). Increased values of total benzo(a)pyrene equivalents (p = 0.101), dose rates (p < 0.001), and carcinogenic risks (p = 0.063) were estimated in firefighters during controlled fires comparatively with the control group. Firefighters' breathable gaseous phase collected during fire events contributed to induce a significant viability decrease (<70 %; p < 0.05) in A549 and Calu-3 cell lines. The principal component analysis (PCA) allowed the differentiation between firefighters participating in controlled fire events from the control group. PCA analysis demonstrated the potential of PAHs to distinguish different sources of firefighters´ occupational exposure and of combining estimated health risk parameters with in vitro toxicities determined with human-breathable air collected during real-life scenarios. Overall, the participation in controlled fire events contributes to the respiratory health burden of firefighting forces. However, more studies are needed to corroborate these preliminary findings, explore the respiratory toxicological mechanisms, and support the implementation of preventive actions and mitigation strategies to pursue firefighters' health.

Attitudes and Beliefs of Wildland Firefighters Toward Occupational Health Services

CONTEXT

Wildland firefighters (WLFFs) are at an increased risk of health conditions, injuries, and illnesses related to sustained levels of intense physical activity. The purpose of this study was to identify and explore the current attitudes and beliefs of WLFFs regarding health services. Methods: We used consensual qualitative research design for this study. Participants engaged in an online, semistructured interview. Results: We identified four domains: (1) risk mitigation strategies, (2) culture of fire services, (3) access to health care services, and 4) identification of health care gap. Conclusions: Access to occupational health services for WLFFs is readily available in the form of emergency medical care. However, a lack of regular access to physical medicine and the continuation of care beyond acute treatment was apparent.

Air pollution inside fire stations: State-of-the-art and future challenges

Firefighters are frequently exposed to products of combustion and pyrolysis. Exposure to these substances occurs not only during fires but also at fire stations, particularly where fire equipment and fire uniforms are stored after firefighting operations. The aims of this study were to review the research on the concentrations of various air pollutants in fire stations, identify the limitations and strengths of such research, identify research gaps and related future challenges, and highlight potential solutions for reducing firefighter exposure to air pollution at fire stations. A total of 32 articles published in international journals during 1987-2023 were selected for analysis. The most frequently studied pollutants in fire stations were polycyclic aromatic hydrocarbons, particulate matter, and diesel particulate matter. Research was most often conducted on changing rooms and garages. Firefighting equipment, personal protective equipment, fire trucks, and combustion tools were identified as the main sources of pollution at fire stations. Recommendations aimed at reducing the concentration of pollutants in fire stations were mainly concerned with the systematic decontamination of equipment and the introduction of ventilation solutions that would remove exhaust fumes from garages. This in-depth literature review indicates a lack of comprehensive research on the state and quality of air at fire stations. It also highlights the emerging need for more knowledge on the concentrations of air pollutants in fire stations, health exposure related to these substances, and an analysis of the effectiveness of the proposed solutions.

Update on Lung Cancer Screening Guideline

Lung cancer screening has been shown to reduce lung cancer mortality and is recommended for individuals meeting age and smoking history criteria. Despite the expansion of lung cancer screening guidelines in 2021, racial/ethnic and sex disparities persist. High-risk racial minorities and women are more likely to be diagnosed with lung cancer at younger ages and have lower smoking histories when compared with White and male counterparts, resulting in higher rates of ineligibility for screening. Risk prediction models, biomarkers, and deep learning may help refine the selection of individuals who would benefit from screening.

Connections Between Air Pollution, Climate Change, and Cardiovascular Health

Globally, more people die from cardiovascular disease than any other cause. Climate change, through amplified environmental exposures, will promote and contribute to many noncommunicable diseases, including cardiovascular disease. Air pollution, too, is responsible for millions of deaths from cardiovascular disease each year. Although they may appear to be independent, interchangeable relationships and bidirectional cause-and-effect arrows between climate change and air pollution can eventually lead to poor cardiovascular health. In this topical review, we show that climate change and air pollution worsen each other, leading to several ecosystem-mediated effects. We highlight how increases in hot climates as a result of climate change have increased the risk of major air pollution events such as severe wildfires and dust storms. In addition, we show how altered atmospheric chemistry and changing patterns of weather conditions can promote the formation and accumulation of air pollutants: a phenomenon known as the climate penalty. We demonstrate these amplified environmental exposures and their associations to adverse cardiovascular health outcomes. The community of health professionals-and cardiologists, in particular-cannot afford to overlook the risks that climate change and air pollution bring to the public's health.

Wildland Firefighter Critical Training Elicits Positive Adaptations to Markers of Cardiovascular and Metabolic Health

INTRODUCTION

The purpose of this study was to identify physiologic changes in body composition and resting metabolic markers of health across 2 wk of critical training (CT) in wildland firefighters (WLFFs).

METHODS

Twenty-two male and 3 female participants were recruited from 2 hotshot crews across the western United States prior to the 2022 fire season and monitored over their 80-h CT. Body weight (BW) and skinfolds were recorded before and after CT to estimate body fat (BF) and lean body weight (LBW). Blood was analyzed for changes in hematocrit, hemoglobin, plasma volume, and resting values of a lipid and metabolic panel.

RESULTS

The high physical demands of CT resulted in improvements in total cholesterol (-19.3 mg/dL, P<0.001), triglycerides (-34.4 mg/dL, P<0.001), low-density lipoprotein cholesterol (-18.1 mg/dL, P<0.001), very-low-density lipoprotein cholesterol (-5.2 mg/dL, P<0.001), high-density lipoprotein cholesterol (+4.0 mg/dL, P=0.002), non-high-density lipoprotein cholesterol (-19.3 mg/dL, P<0.001), and fasting glucose (-4.3 mg/dL, P=0.008) from before CT to after CT. Significant decreases in hemoglobin and hematocrit were also seen (P<0.001) with corresponding increases in estimated plasma volume (+6.1%, P<0.001). These alterations were seen despite maintenance of BW, LBW, and BF. Lower pretraining BF was associated with a greater magnitude of improvements in fasting glucose and cholesterol markers.

CONCLUSIONS

The observed improvements in baseline metabolic and cardiovascular markers along with plasma volume expansion suggest a positive response to the physical stress of WLFF CT. It appears that higher preseason fitness was associated with greater adaptations to the CT stressor.

Lung cancer survival among Florida male firefighters

Introduction

Lung cancer is a leading cause of cancer incidence and death in the United States. Although most firefighters are fit and do not smoke, they are exposed to many known carcinogens during and in the aftermath of firefighting activities. Comprehensive epidemiologic investigations on lung cancer survival for both career and volunteer firefighters have not been undertaken.

Methods

Data from the Florida Cancer Data System (1981-2014) were linked with firefighter certification records from the Florida State Fire Marshal's Office to identify all patients of this occupational group; lung cancer cause-specific survival data were compared with other occupational groups using Cox regression models with occupation as the main effect. Adjusted hazard ratios (aHR) and 95% confidence intervals (95% CI) were calculated.

Results

Out of 210,541 male lung cancer cases diagnosed in Florida (1981-2014), 761 were firefighters (604 career, 157 volunteer). Lung cancer death was similar between volunteer (75.2%) and career firefighters (74.0%) but lower than non-firefighters (80.0%). Survival at 5 years was higher among firefighters (29.7%; career: 30.3%; volunteer: 27.4%) than non-firefighters (23.8%). In a multivariable model, compared with non-firefighters, firefighters have significantly higher cause-specific survival (aHR = 0.84; 95% CI: 0.77-0.91; p < 0.001). However, there were no significant survival differences between career and volunteer firefighters (1.14; 0.93-1.39; p = 0.213). In a separate multivariable model with firefighters as the comparator, other broad occupational groups had significantly lower cause-specific survival [white collar: 1.11 (1.02-1.21); blue collar: 1.15 (1.05-1.25); service: 1.13 (1.03-1.25); others/unknown: 1.21 (1.12-1.32); all p-values < 0.02].

Conclusion

Lung cancer survival is significantly higher among firefighters compared with non-firefighters, but there is no significant difference between career and volunteer firefighters. Improved survival for firefighters might be due to a healthy worker effect, lower smoking prevalence relative to other worker groups, and possibly superior treatment adherence and compliance. Many firefighters are cross-trained as EMTs/paramedics and possess a level of medical knowledge that may favorably impact treatment engagement and better navigation of complex cancer care.

Assessment of coarse, fine, and ultrafine particulate matter at different microenvironments of fire stations

The concentrations of respirable particulate matter (PM) and the impact on indoor air quality in occupational settings remains poorly characterized. This study assesses, for the first time, the cumulative and non-cumulative concentrations of 14 fractions of coarse (3.65-9.88 μm), fine (0.156-2.47 μm), and ultrafine (0.015-0.095 μm) PM inside the garage of heavy vehicles, firefighting personal protective equipment' storage room, bar, and a common area of seven Portuguese fire stations. Sampling campaigns were performed during a regular work week at the fire stations. Levels of daily total cumulative PM ranged from 277.4 to 413.2 μg/m³ (maximum values of 811.4 μg/m³), with the bar (370.1 μg/m³) and the PPE' storage room (361.3 μg/m³) presenting slightly increased levels (p > 0.05) than the common area (324.8 μg/m³) and the garage (339.4 μg/m³). The location of the sampling site, the proximity to local industries and commercial activities, the layout of the building, the heating system used, and indoor sources influenced the PM concentrations. Fine (193.8-301.0 μg/m³) and ultrafine (41.3-78.2 μg/m³) particles were predominant in the microenvironments of all fire stations and accounted for 71.5% and 17.8% of daily total cumulative levels, respectively; coarse particles (23.3-47.1 μg/m³) represented 10.7% of total PM. The permissible exposure limit (5.0 mg/m³) defined by the Occupational Safety and Health Organization for respirable dust was not overcome in the evaluated fire stations. Results suggest firefighters' regular exposure to fine and ultrafine PM inside fire stations which will contribute to cardiorespiratory health burden. Further studies are needed to characterize firefighters' exposure to fine and ultrafine PM inside fire stations, identify main emission sources, and evaluate the contribution of exposures at fire stations to firefighters' occupational health risks.

In vitro data for fire pollutants: contribution of studies using human cell models towards firefighters' occupational

Firefighters are the principal line of defense against fires, being at elevated risk of exposure to health-relevant pollutants released during fires and burning processes. Although many biomonitoring studies exist, only a limited number of human in vitro investigations in fire risk assessment are currently available. In vitro studies stand out as valuable tools to assess the toxicity mechanisms involved following exposure to fire pollutants at a cellular level. The aim of the present review was to contextualize existing in vitro studies using human cell models exposed to chemicals emitted from fire emissions and wood smoke and discuss the implications of the observed toxic outcomes on adverse health effects detected in firefighters. Most of the reported in vitro investigations focused on monocultures respiratory models and exposure to particulate matter (PM) extracts collected from fire effluents. Overall, (1) a decrease in cellular viability, (2) enhanced oxidative stress, (3) increased pro-inflammatory cytokines levels and (4) elevated cell death frequencies were noted. However, limited information remains regarding the toxicity mechanisms initiated by firefighting activities. Hence, more studies employing advanced in vitro models and exposure systems using human cell lines are urgently needed taking into consideration different routes of exposure and health-related pollutants released from fires. Data are needed to establish and define firefighters' occupational exposure limits and to propose mitigation strategies to promote beneficial human health.

Face-to-face with scorching wildfire: potential toxicant exposure and the health risks of smoke for wildland firefighters at the wildland-urban interface

As wildfire risks have elevated due to climate change, the health risks that toxicants from fire smoke pose to wildland firefighters have been exacerbated. Recently, the International Agency for Research on Cancer (IARC) has reclassified wildland firefighters' occupational exposure as carcinogenic to humans (Group 1). Wildfire smoke contributes to an increased risk of cancer and cardiovascular disease, yet wildland firefighters have inadequate respiratory protection. The economic cost of wildland fires has risen concurrently, as illustrated by the appropriation of $45 billion for wildfire management over FYs 2011-2020 by the U.S. Congress. Occupational epidemiological studies of wildland firefighters are crucial for minimizing health risks; however, they must account for the mixture of exposures in wildfire smoke. This review focuses on four aspects of wildland firefighters' health risks at the wildland-urban interface: 1) economic costs and health impact, 2) respiratory protection, 3) multipollutant mixtures, and 4) proactive management of wildfires.

Biomonitoring of firefighting forces: a review on biomarkers of exposure to health-relevant pollutants released from fires

Occupational exposure as a firefighter has recently been classified as a carcinogen to humans by International Agency for Research on Cancer (IARC). Biomonitoring has been increasingly used to characterize exposure of firefighting forces to contaminants. However, available data are dispersed and information on the most relevant and promising biomarkers in this context of firefighting is missing. This review presents a comprehensive summary and critical appraisal of existing biomarkers of exposure including volatile organic compounds such as polycyclic aromatic hydrocarbons, several other persistent other organic pollutants as well as heavy metals and metalloids detected in biological fluids of firefighters attending different fire scenarios. Urine was the most characterized matrix, followed by blood. Firefighters exhaled breath and saliva were poorly evaluated. Overall, biological levels of compounds were predominantly increased in firefighters after participation in firefighting activities. Biomonitoring studies combining different biomarkers of exposure and of effect are currently limited but exploratory findings are of high interest. However, biomonitoring still has some unresolved major limitations since reference or recommended values are not yet established for most biomarkers. In addition, half-lives values for most of the biomarkers have thus far not been defined, which significantly hampers the design of studies. These limitations need to be tackled urgently to improve risk assessment and support implementation of better more effective preventive strategies.

Prolonged smoldering Douglas fir smoke inhalation augments respiratory resistances, stiffens the aorta, and curbs ejection fraction in hypercholesterolemic mice

While mounting evidence suggests that wildland fire smoke (WFS) inhalation may increase the burden of cardiopulmonary disease, the occupational risk of repeated exposure during wildland firefighting remains unknown. To address this concern, we evaluated the cardiopulmonary function in mice following a cumulative exposure to lab-scale WFS equivalent to a mid-length wildland firefighter (WLFF) career. Dosimetry analysis indicated that 80 exposure hours at a particulate concentration of 22 mg/m3 yield in mice the same cumulative deposited mass per unit of lung surface area as 3600 h of wildland firefighting. To satisfy this condition, male Apoe-/- mice were whole-body exposed to either air or smoldering Douglas fir smoke (DFS) for 2 h/day, 5 days/week, over 8 consecutive weeks. Particulate size in DFS fell within the respirable range for both mice and humans, with a count median diameter of 110 ± 20 nm. Expiratory breath hold in mice exposed to DFS significantly reduced their minute volume (DFS: 27 ± 4; Air: 122 ± 8 mL/min). By the end of the exposure time frame, mice in the DFS group exhibited a thicker (DFS: 109 ± 3; Air: 98 ± 3 μm) and less distensible (DFS: 23 ± 1; Air: 28 ± 1 MPa-1) aorta with reduced diastolic blood augmentation capacity (DFS: 53 ± 2; Air: 63 ± 2 kPa). Cardiac magnetic resonance imaging further revealed larger end-systolic volume (DFS: 14.6 ± 1.1; Air: 9.9 ± 0.9 μL) and reduced ejection-fraction (DFS: 64.7 ± 1.0; Air: 75.3 ± 0.9 %) in mice exposed to DFS. Consistent with increased airway epithelium thickness (DFS: 10.4 ± 0.8; Air: 7.6 ± 0.3 μm), airway Newtonian resistance was larger following DFS exposure (DFS: 0.23 ± 0.03; Air: 0.20 ± 0.03 cmH2O-s/mL). Furthermore, parenchyma mean linear intercept (DFS: 36.3 ± 0.8; Air: 33.3 ± 0.8 μm) and tissue thickness (DFS: 10.1 ± 0.5; Air: 7.4 ± 0.7 μm) were larger in DFS mice. Collectively, mice exposed to DFS manifested early signs of cardiopulmonary dysfunction aligned with self-reported events in mid-career WLFFs.