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.

Risk Factors Associated with Suicidal Ideation and Suicidal Behavior in Wildland Firefighters.

INTRODUCTION: Wildland firefighters are posited to have a higher suicide rate than general firefighters and the general population. However, the rates and risk factors of suicide among wildland firefighters is not fully understood. METHODS: For this preregistered study, 564 participants were recruited from Facebook to obtain a final sample of 246 participants with valid data who were current or former wildland firefighters in the United States. Participants completed online measures of suicidal ideation, history of suicidal behaviors, posttraumatic stress disorder (PTSD) symptoms, problematic alcohol use, and occupational exposure to suicide. RESULTS: In this sample, 22% of wildland firefighters reported a history of at least one suicide attempt, and 36.7% reported current suicidal ideation. PTSD symptoms, but not problematic alcohol use or exposure to suicide, were positively associated with suicidal ideation and a history of suicide attempts. Additionally, PTSD symptoms explained significantly more variance in suicidal ideation than depression symptoms alone. CONCLUSIONS: Wildland firefighters demonstrate rates of suicide attempts that exceed those of non-wildland firefighters and of the general population at large. In addition, PTSD symptoms may contribute to suicidal thoughts and behaviors (STB) in this population. This is the largest study of STB in wildland firefighters to date.

A Web-Based Total Worker Health Intervention for Those Fighting Wildland Fires: Mixed Methods Development and Effectiveness Trial.

BACKGROUND: Fire seasons are longer, with more and larger wildfires, placing increased demands and risks on those fighting wildland fires. There are multiple agencies involved with fighting wildland fires and unique worksite conditions make meeting these workers' needs a challenge. OBJECTIVE: The aim of the study is to develop and establish the effectiveness of a web-based safety and health program for those fighting wildland fires. METHODS: This mixed methods project had 3 phases. The initial qualitative phase assessed the needs of 150 diverse firefighters through interviews and focus groups across 11 US sites to establish and prioritize program content. Interview transcripts were read for thematic content with iterative readings used to identify, code, and rank health and safety issues. The second phase used that information to build a comprehensive Total Worker Health program for those fighting wildfires. The program content was based on the qualitative interview data and consisted of 6 core and 8 elective 30-minute, web-based modules primarily done individually on a smartphone or computer. The final, third phase evaluated the program with a quantitative prospective proof-of-concept, usability, and effectiveness trial among wildland firefighter participants. Effectiveness was assessed with paired 2-tailed t tests for pre- and post-Likert agreement scale survey items, adjusted for multiple comparisons. In addition to assessing mean and SD at baseline and postsurvey, observed effect sizes were calculated (Cohen d). Usability and reaction to the program among firefighters who responded to postsurvey were also assessed. RESULTS: The qualitative themes and subthemes were used to inform the program's content. For the effectiveness trial, 131 firefighters completed the presurvey, and 50 (38.2%) completed the postsurvey. The majority of the participants were White (n=123, 93.9%), male (n=117, 89.3%), with an average age of 41 (SD 12.9) years. Significant increases in knowledge and desired health and safety behaviors were found for both cancer (P<.001) and cardiovascular risk (P=.01), nutrition behaviors (P=.01), hydration or overheating (P=.001), binge drinking (P=.002), and getting medical checkups (P=.001). More than 80% (n=40) of postsurvey respondents agreed or strongly agreed that the program was easy to use and would recommend it to others. CONCLUSIONS: An innovative web-based safety and health promotion program for those fighting wildland fires was feasible, scalable, and usable. It improved the health and safety of those fighting wildland fires. TRIAL REGISTRATION: ClinicalTrials.gov NCT05753358; https://classic.clinicaltrials.gov/ct2/show/NCT05753358.

The Urgent Need for Cardiopulmonary Fitness Evaluation among Wildland Firefighters in Thailand.

Wildland firefighting is a high-risk occupation. The level of cardiopulmonary fitness can indicate whether wildland firefighters are ready to perform their job duties. This study's objective was to determine wildland firefighters' cardiopulmonary fitness using practical methods. This cross-sectional descriptive study aimed to enroll all 610 active wildland firefighters in Chiang Mai. The participants' cardiopulmonary fitness was assessed using an EKG, a chest X-ray, a spirometry test, a global physical activity questionnaire, and the Thai score-based cardiovascular risk assessment. The NFPA 1582 was used to determine "fitness" and "job restriction". Fisher's exact and Wilcoxon rank-sum tests were used to compare cardiopulmonary parameters. With a response rate of 10.16%, only eight wildland firefighters met the cardiopulmonary fitness requirements. Eighty-seven percent of participants were in the job-restriction group. An aerobic threshold of eight METs, an abnormal EKG, an intermediate CV risk, and an abnormal CXR were the causes of restriction. The job-restriction group had a higher 10-year CV risk and higher systolic blood pressure, although these differences were not statistically significant. The wildland firefighters were unfit for their task requirements and were more at risk of cardiovascular health compared to the estimated risk of the general Thai population. To improve the health and safety of wildland firefighters, pre-placement exams and health surveillance are urgently needed.

Examining the effects of a weighted pack on functional movements in smokejumpers.

BACKGROUND: Smokejumpers are required to parachute from planes, carry gear weighing more than 50 kg, and hike on steep terrain. With a majority of injuries sustained to the lower extremity, it is imperative to understand the influence a weighted pack may have on functional performance. OBJECTIVE: To examine the effects of external load on functional movements in Smokejumpers. METHODS: Using repeated measures design, ten Smokejumpers completed two trials consisting of 3 movements in weighted (50 kg) and unweighted conditions. Nine males and one female (age of 40.1±8.4 years, mass 81.1±8.3 kg) performed overhead squat, hurdle step and anterior reach. Movements were scored based on established guidelines. The mean of three trials was recorded for anterior reach on both limbs. RESULTS: Differences between weighted and unweighted scores in the overhead squat (p = 0.001), ND hurdle step (p = 0.005), D hurdle step (p = 0.000) and overall composite scores (p = 0.006) were found to be significantly different. Differences were also noted in D (p = 0.035) and ND (p = 0.045) anterior reach. CONCLUSIONS: The addition of a weighted pack negatively influences functional movements in Smokejumpers, which may lead to greater injury risk. Implementation of injury prevention strategies to reduce occupational injury risk should be explored.

Health risks and mitigation strategies from occupational exposure to wildland fire: a scoping review.

OBJECTIVES: Due to accelerating wildland fire activity, there is mounting urgency to understand, prevent, and mitigate the occupational health impacts associated with wildland fire suppression. The objectives of this review of academic and grey literature were to: 1. Identify the impact of occupational exposure to wildland fires on physical, mental, and emotional health; and 2. Examine the characteristics and effectiveness of prevention, mitigation, or management strategies studied to reduce negative health outcomes associated with occupational exposure to wildland fire. METHODS: Following established scoping review methods, academic literature as well as government and industry reports were identified by searching seven academic databases and through a targeted grey literature search. 4679 articles were screened using pre-determined eligibility criteria. Data on study characteristics, health outcomes assessed, prevention or mitigation strategies studied, and main findings were extracted from each included document. The results of this scoping review are presented using descriptive tables and a narrative summary to organize key findings. RESULTS: The final sample was comprised of 100 articles: 76 research articles and 24 grey literature reports. Grey literature focused on acute injuries and fatalities. Health outcomes reported in academic studies focused on respiratory health (n = 14), mental health (n = 16), and inflammation and oxidative stress (n = 12). The identified studies evaluated short-term outcomes measuring changes across a single shift or wildland fire season. Most research was conducted with wildland firefighters and excluded personnel such as aviation crews, contract crews, and incident management teams. Five articles reported direct study of mitigation strategies, focusing on the potential usage of masks, advanced hygiene protocols to reduce exposure, fluid intake to manage hydration and core temperature, and glutamine supplementation to reduce fatigue. CONCLUSIONS: While broad in scope, the evidence base linking wildland fire exposure to any one health outcome is limited. The lack of long-term evidence on changes in health status or morbidity is a clear evidence gap and there is a need to prioritize research on the mental and physical health impact of occupational exposure to wildland fire.

Acute cardiovascular responses of wildland firefighters to working at prescribed burn.

Wildland firefighters at prescribed burns are exposed to elevated levels of wildland fire smoke (WFS) while performing physically demanding tasks. WFS exposure has been linked to increases in hospital and emergency admissions for cardiovascular disorders in the general population. However, knowledge about the cardiovascular effect of occupational WFS exposure among wildland firefighters is limited. To provide a better understanding of the effect of this exposure scenario on acute hemodynamic responses, resting systolic/diastolic blood pressure (SBP/DBP) and heart rate (HR) of wildland firefighters were measured before (pre-shift), after (post-shift), and the morning (next morning) immediately following prescribed burn shifts (burn days) and regular work shifts (non-burn days). A total of 38 firefighters (34 males and 4 females) participated in this study and resting BP and HR were recorded on 9 burn days and 7 non-burn days. On burn days, HR significantly increased from pre-to post-shift (13.25 bpm, 95% CI: 7.47 to 19.02 bpm) while SBP significantly decreased in the morning following the prescribed burns compared to pre-shift (-6.25 mmHg, 95% CI: -12.30 to -0.20 mmHg). However, this was due to the decrease of SBP in the firefighters who were hypertensive (-8.46 mmHg, 95% CI: -16.08 to -0.84 mmHg). Significant cross-shift reductions (post-shift/next morning vs. pre-shift) were observed in SBP on burn days compared to non-burn days (-7.01 mmHg, 95% CI: -10.94 to -3.09 mmHg and -8.64 mmHg, 95% CI: -13.81 to -3.47 mmHg, respectively). A significant reduction on burn days was also observed from pre-shift to the following morning for HR compared to non-burn days (-7.28 bpm, 95% CI: -13.50 to -1.06 bpm) while HR significantly increased in pre-to post-shift on burn days compared to non-burn days (10.61 bpm, 95% CI: 5.05 to 16.17 bpm). The decreased BP observed in wildland firefighters might be due to a high level of carbon monoxide exposure and exercise-induced hypotension. The increase in HR immediately after prescribed burns might be attributable to WFS exposure and physical exertion in prescribed burn shifts. The results suggest that wildland firefighting exposure might cause a distinct hemodynamic response, including SBP reduction and HR increment, especially for those who have pre-existing hypertension.

Carbon monoxide exposures in wildland firefighters in the United States and targets for exposure reduction.

BACKGROUND: Every year thousands of wildland firefighters (WFFs) work to suppress wildfires to protect public safety, health, and property. Although much effort has been put toward mitigating air pollutant exposures for the public and WFFs, the current burden in this worker population is unclear as are the most effective exposure reduction strategies. OBJECTIVE: Quantify fireline carbon monoxide (CO) exposures in WFFs and identify predictors of exposures. METHODS: We collected 1-min breathing zone CO measurements on 246 WFFs assigned to fires between 2015 and 2017. We used generalized estimating equations to evaluate predictors of CO exposure. RESULTS: Approximately 5% of WFFs had fireline CO exposure means exceeding the National Wildfire Coordinating Group's occupational exposure limit of 16 ppm. Relative to operational breaks, direct suppression-related job tasks were associated with 56% (95% CI: 47%, 65%) higher geometric mean CO concentrations, adjusted for incident type, crew type, and fire location. WFF perception of smoke exposure was a strong predictor of measured CO exposure. SIGNIFICANCE: Specific job tasks related to direct suppression and WFF perceptions of smoke exposure are potential opportunities for targeted interventions aimed at minimizing exposure to smoke.

Exposure and Absorption of PAHs in Wildland Firefighters: A Field Study with Pilot Interventions.

OBJECTIVES: There is limited knowledge of exposure to polycyclic aromatic hydrocarbons (PAHs) in wildland firefighters, or of the effectiveness of interventions to reduce this. This study of wildland firefighters assessed whether PAHs were present and considered respiratory protection and enhanced skin hygiene as possible interventions. METHODS: 1-Hydroxypyrene (1-HP) was measured in urine samples collected pre-shift, post-shift, and next morning from wildland firefighters in Alberta and British Columbia. Skin wipes, collected pre- and post-shift, were analysed for eight PAHs. Breathing zone air samples were analysed for 11 PAHs. As pilot interventions, participants were randomized to either normal or enhanced skin hygiene. A sample of volunteers was assigned to a disposable N95 mask or a half facepiece mask with P100 organic vapour cartridge. Participants completed a brief questionnaire on activities post-shift and respiratory symptoms. RESULTS: Non-smoking firefighters (66 male and 20 female) were recruited from 11 fire crews. Air sampling pumps were carried for the full shift by 28 firefighters, 25 firefighters wore masks (14 N95 and 11 P100); 42 were assigned to the enhanced skin hygiene intervention. Sixty had hot spotting as their main task. Air monitoring identified PAHs (benzo(b,j,k)fluoranthene in particulates, phenanthrene in the gaseous phase) for 6 of the 11 crews. PAHs (largely naphthalene) were found post-shift on 40/84 skin wipes from the hand and 38/84 from jaw/throat. The mean increase in 1-HP in urine samples collected after the shift (compared with samples collected before the shift) was 66 ng g-1 creatinine (P < 0.001) with an increase over the shift found for 76% of participants. 1-HP in next morning urine samples was significantly lower than at the end of shift (a reduction of 39.3 ng g-1: P < 0.001). The amount of naphthalene on skin wipes was greater at the end of the shift (post) than at the start (pre). The mean post-pre weight difference of naphthalene on skin wipes taken from the hand was 0.96 ng wipe-1 (P = 0.01) and from the jaw/throat 1.28 ng wipe-1 (P = 0.002). The enhanced skin hygiene intervention lead to a larger reduction in 1-HP between end of shift and next morning urine samples but only for those with naphthalene on skin wipes at the end of shift. The difference in 1-HP concentration in urine samples collected before and after the shift was reduced for those wearing a mask (linear tend P = 0.063, one-sided). In multivariable models, 1-HP at end of shift was related to gaseous phase phenanthrene, estimated from air sampling [ß = 318.2, 95% confidence interval (CI) 67.1-569.2]. Naphthalene on hand skin wipes reflected work in hot spotting during the shift (ß = 0.53, 95% CI 0.22-0.86). CONCLUSIONS: This study provided evidence of PAHs in the air and on the skin of many, but not all, fire crew. Absorbed PAHs, reflected in 1-HP in urine, increased over the shift. Results from the pilot interventions suggest that enhanced skin hygiene would reduce absorption post fire where PAHs had been accumulated on the skin, and that masks could be effective in reducing PAH inhalation exposure. Interventions to reduce PAH absorption are supported by the pilot work reported here and warrant further evaluation across a full fire season.

Measuring acute pulmonary responses to occupational wildland fire smoke exposure using exhaled breath condensate.

Wildland firefighters are directly exposed to elevated levels of wildland fire (WF) smoke. Although studies demonstrate WF smoke exposure is associated with lung function changes, few studies that use invasive sample collection methods have been conducted to investigate underlying biochemical changes. These methods are also either unrepresentative of the deeper airways or capable of inducing inflammation. In the present study, levels of biomarkers of oxidative stress (8-isoprostane) and pro-inflammatory response (interleukin-6 [IL-6], interleukin-8 [IL-8], C-reactive protein [CRP], and soluble intercellular adhesion molecule-1 [sICAM-1]) were determined in exhaled breath condensate (EBC) samples that were collected from firefighters before, after, and next morning following prescribed burn and regular work shifts. Results show only a marginal cross-shift increase in 8-isoprostane on burn days (.05 < p value < .1), suggesting WF smoke exposure causes mild pulmonary responses.

Comparison of Sports Drink Versus Oral Rehydration Solution During Exercise in the Heat.

INTRODUCTION: This study compared 2 commercially available beverages, an oral rehydration solution (ORS; 60.9 mM Na+; 3.4% carbohydrate) and a sports drink (SDS; 18.4 mM Na+; 5.9% carbohydrate), on hydration and metabolism during submaximal exercise in the heat. METHODS: Ten male subjects completed two 90-min exercise trials (39ºC, 30%) of walking at 50% VO2max followed by a 30-min rest period in the heat while wearing wildland firefighter personal protective clothing. After 45 min of exercise, fluid delivery by either ORS or SDS replaced 150% of sweat loss. Subjects continued the exercise for 45 additional minutes followed by a 30-min rest period. Blood samples were collected pre-exercise (0 min), post-exercise (90 min), and post-trial (120 min) to measure plasma volume (%) and blood glucose (mg·dL-1). Expired gases were collected twice for 3 min for substrate oxidation. RESULTS: The sweat rate and percent dehydration did not differ between the groups (P=0.86 and P=0.79, respectively). Changes in plasma volume did not differ (P=0.55). Hemoglobin levels significantly increased in both groups post-trial (P=0.009). Blood glucose was significantly greater post-trial in SDS versus ORS (116±19 vs 103±13 mg·dL-1, respectively; P=0.01). Fat oxidation was lower post-exercise in SDS vs ORS (0.38±0.1 vs 0.47±0.2 g·min-1, respectively; P=0.049). CONCLUSIONS: These data indicate no difference in fluid retention between ORS or SDS when supplemented during exercise in the heat. This implies that fluid volume, and not drink contents, may be more important when ingested during exercise in a hot environment.

Influence of work clothing on physiological responses and performance during treadmill exercise and the Wildland Firefighter Pack Test.

This study investigated physiological responses and performance during three separate exercise challenges (Parts I, II, and III) with wildland firefighting work clothing ensemble (boots and coveralls) and a 20.4 kg backpack in four conditions: U-EX (no pack, exercise clothing); L-EX (pack, exercise clothing); U-W (no pack, work clothing); and, L-W (pack and work clothing). Part I consisted of randomly-ordered graded exercise tests, on separate days, in U-EX, L-EX and L-W conditions. Part II consisted of randomly-ordered bouts of sub-maximal treadmill exercise in the four conditions. In Part III, subjects completed, in random-order on separate days, 4.83 km Pack Tests in L-EX or L-W conditions. In Part I, peak oxygen uptake was reduced (p < .05) in L-W. In Part II, mass-specific oxygen uptake was significantly higher in both work clothing conditions. In Part III, Pack Test time was slower (p < .05) in L-W. These results demonstrate the negative impact of work clothing and load carriage on physiological responses to exercise and performance.

Wildland firefighter deaths in the United States: A comparison of existing surveillance systems.

Wildland fire fighting is a high-risk occupation requiring considerable physical and psychological demands. Multiple agencies publish fatality summaries for wildland firefighters; however, the reported number and types vary. At least five different surveillance systems capture deaths, each with varying case definitions and case inclusion/exclusion criteria. Four are population-level systems and one is case-based. System differences create challenges to accurately characterize fatalities. Data within each of the five surveillance systems were examined to better understand the types of wildland firefighter data collected, to assess each system's utility in characterizing wildland firefighter fatalities, and to determine each system's potential to inform prevention strategies. To describe similarities and differences in how data were recorded and characterized, wildland fire deaths for three of the population-based systems were matched and individual fatalities across systems were compared. Between 2001 and 2012, 247 unique deaths were captured among the systems; 73% of these were captured in all three systems. Most common causes of death in all systems were associated with aviation, vehicles, medical events, and entrapments/burnovers. The data show that, although the three systems often report similar annual summary statistics, events captured in each system vary each year depending on the types of events that the system is designed to track, such as inclusion/exclusion of fatalities associated with the Hometown Heroes Survivor Benefits Act of 2003. The overarching and central goal of each system is to collect accurate and timely information to improve wildland firefighter safety and health. Each system is unique and has varying inclusion and exclusion criteria for capturing and tracking different subsets of wildland firefighter tasks and duties. Use of a common case definition and better descriptions and interpretations of the data and the results would help to more accurately characterize wildland firefighter traumatic injuries and illnesses, lessen the likelihood for misinterpretation of wildland firefighter fatality data, and assist with defining the true occupational injury burden within this high-risk population.

Review of the health effects of wildland fire smoke on wildland firefighters and the public.

Each year, the general public and wildland firefighters in the US are exposed to smoke from wildland fires. As part of an effort to characterize health risks of breathing this smoke, a review of the literature was conducted using five major databases, including PubMed and MEDLINE Web of Knowledge, to identify smoke components that present the highest hazard potential, the mechanisms of toxicity, review epidemiological studies for health effects and identify the current gap in knowledge on the health impacts of wildland fire smoke exposure. Respiratory events measured in time series studies as incidences of disease-caused mortality, hospital admissions, emergency room visits and symptoms in asthma and chronic obstructive pulmonary disease patients are the health effects that are most commonly associated with community level exposure to wildland fire smoke. A few recent studies have also determined associations between acute wildland fire smoke exposure and cardiovascular health end-points. These cardiopulmonary effects were mostly observed in association with ambient air concentrations of fine particulate matter (PM2.5). However, research on the health effects of this mixture is currently limited. The health effects of acute exposures beyond susceptible populations and the effects of chronic exposures experienced by the wildland firefighter are largely unknown. Longitudinal studies of wildland firefighters during and/or after the firefighting career could help elucidate some of the unknown health impacts of cumulative exposure to wildland fire smoke, establish occupational exposure limits and help determine the types of exposure controls that may be applicable to the occupation.

Exposure of wildland firefighters to carbon monoxide, fine particles, and levoglucosan.

Wildland firefighters are occupationally exposed to elevated levels of woodsmoke. Eighteen wildland firefighters were monitored for their personal exposure to particulate matter with median aerodynamic diameter of 2.5 microns (PM2.5), levoglucosan (LG), and carbon monoxide (CO) at 30 prescribed burns at the Savannah River Site, South Carolina. Linear mixed effect models were used to investigate the effect on exposure of various factors and to examine whether the firefighters were able to qualitatively estimate their own exposures. Exposure to PM2.5 and CO was higher when firefighters performed 'holding' tasks compared with 'lighting' duties, whereas exposures to CO and LG were higher when burns were in compartments with predominantly pine vegetation (P < 0.05). Exposures to PM2.5 (64-2068 µg m(-3)) and CO (0.02-8.2 p.p.m.) fell within the ranges observed in previous studies. Some recommended shorter term exposure limits for CO were exceeded in a few instances. The very low LG:PM2.5 ratios in some samples suggest that the exposures of wildland firefighters to pollutants at prescribed burns may be substantially impacted by non-woodsmoke sources. The association of the qualitative exposure estimation of the firefighters with actual PM2.5 and CO measurements (P < 0.01) indicates that qualitative estimation may be used to assess exposure in epidemiology studies.