Firefighting and Cancer: A Meta-analysis of Cohort Studies in the Context of Cancer Hazard Identification

Human exposure to polycyclic aromatic hydrocarbons during structure fires: Concentrations outside and inside self-contained breathing apparatus and in vitro respiratory toxicity

Structure fires release several health-hazardous compounds, including polycyclic aromatic hydrocarbons (PAHs), and the use of self-contained breathing apparatus (SCBA) is mandatory to protect firefighters' airways. The characterization of PAHs released during structure fires is scarce, principally in European countries. This work elucidates the mechanisms of toxic effects associated with human exposure to PAHs released during structure fires, by assessing for the first time, the levels in the breathable air of sapper firefighters with and without the use of SCBA. An in vitro co-culture model of air-blood barrier was used to evaluate respiratory toxicity. Concentrations of total PAHs (∑PAHs) inside the burning structure were 8.20-19.8 times higher than the values monitored inside fire stations (11.5-28.0 μg/m3versus 1.41 μg/m3; p < 0.005) and 2688-5872 times higher than the levels detected inside the SCBA used during the fire events. Levels of carcinogenic PAHs were 6.90-20.5 times higher than observed for the control group (p ≤ 0.005). Inside to outside ratios (<1) suggested the contribution of PAHs from fires to the levels detected inside the protection system. Exposure to fire emissions increased the risk of lung cancer. The use of SCBA system substantially reduced exposure to PAHs, still levels detected outside/inside the SCBA facemask significantly reduced the viability of alveolar and bronchial cell lines (<70 %). Benzo(a)pyrene (100 %), naphthalene and phenanthrene (97.5 %), benzo(b+j)fluoranthene (90 %), and fluorene (87.5 %) found inside the SCBA mask were able to permeate the co-culture model of air-blood barrier. More studies need to corroborate these preliminary findings and evaluate the synergic effect of fire effluent complex mixtures and their contribution to respiratory toxicity.

Interventions to Reduce Serum Per- and Poly-Fluoroalkyl Substances Levels, Improve Cardiovascular Risk Profiles, and Improve Epigenetic Age Acceleration in US Firefighters: Protocol for Randomized Controlled Trial

BACKGROUND

Occupational cancer and acute cardiac events are the leading causes of death among firefighters. Increased exposure to toxicants on the fire ground, such as polycyclic aromatic hydrocarbons, benzene, and per- and poly-fluoroalkyl substances (PFAS), has been linked to certain cancers, cardiovascular disease, accelerated epigenetic aging, and other adverse health effects. PFAS are a major concern because they are persistent, can bioaccumulate, and are present in several firefighting tools. Compared to the general population, firefighters have elevated serum levels of some types of PFAS. A randomized clinical trial in Australian firefighters found that routine blood and plasma donation for 1 year led to decreased serum PFAS levels, although health outcomes were not directly measured in that study.

OBJECTIVE

In collaboration with fire service leadership in Arizona, the Firefighter Collaborative Research Project (FCRP) was established to evaluate the effectiveness of 3 interventions in a randomized controlled trial design to reduce serum PFAS levels, reduce cancer and cardiovascular risk, and improve overall health and wellness in US firefighters.

METHODS

This study aimed to recruit and enroll up to 1500 active firefighters between August 2023 and October 2024. Between August 2023 and October 2024, active firefighters were recruited and randomized into a study arm based on their eligibility, including serum PFOS levels, for the specific arms. The trial arms include (1) blood and plasma donation, (2) zone 2 physical activity, and (3) intermittent fasting. FCRP outcomes include serum PFAS reduction (arm 1), epigenetic age acceleration (all arms), cardiovascular conditioning (arm 2) and cognitive outcomes (all arms), mental health (all arms), and overall disease risk (all arms). Each study arm includes an intervention and a control group. At enrollment and end of the study, participants provide blood and urine samples and complete a comprehensive questionnaire on their occupational and health history, exposures, and lifestyle behaviors. At the end of the study, participants also participated in a cognitive evaluation. Depending on the study arm, participants may additionally complete a cardiopulmonary exercise test at baseline and follow-up, a mid-study survey, and a mid-study blood and urine collection.

RESULTS

Participant activities and data collection will conclude by December 2025.

CONCLUSIONS

The FCRP is a randomized controlled trial that aims to test the effectiveness of fire service-selected interventions in reducing serum PFAS levels. Study results will contribute to potential interventions that could be used to reduce serum PFAS levels in firefighters.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05869747; https://clinicaltrials.gov/study/NCT05869747.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/67120.

Organizational health culture in the Korean firefighter intervention studies: a scoping review

Introduction

This study examines the current state of intervention studies focused on Korean firefighters, who face unique health challenges due to the demands of their work and specific organizational culture. Recognizing a gap in studies tailored to firefighters' needs, this scoping review aimed to identify existing interventions and provide recommendations for future research.

Methods

Following the Joanna Briggs Institute's methodological guidelines for scoping reviews and the PRISMA-ScR checklist, a seven-stage review was conducted. The search included articles from Korean and international journals published up until January 25, 2024. Data were analyzed using a pre-developed framework and the Template for Intervention Description and Replication checklist. This study was registered on the Open Science Framework (OSF) and is accessible at https://osf.io/s378j/.

Results

From 35 articles analyzed, results showed an imbalance in topics, research design, outcome measures, and intervention delivery methods. Additionally, most studies lacked specific focus on firefighters' unique organizational characteristics and needs.

Discussion

The study highlighted three areas for enhancing intervention research quality: designing and tailoring studies to fit the specific demands of firefighting, ensuring ethical considerations, and aligning with the practical needs of firefighters. Future research should prioritize diverse interventions addressing firefighters' health, incorporate sensitive and ethical research designs, and work closely with experts in firefighting to develop adaptable and relevant interventions.

Systematic Review Registration

https://osf.io/s378j/, Registration DOI: https://doi.org/10.17605/OSF.IO/7EQ8M.

Urology on a changing planet: links between climate change and urological disease

Urological diseases and their varied forms of management warrant special attention in the setting of climate change. Regarding urological cancers, climate change will probably increase the incidence and severity of cancer diagnoses through exposures to certain environmental risk factors, while simultaneously disrupting cancer care delivery and downstream outcomes. Regarding benign urological diseases, a burgeoning body of work exists on climate-related heat waves, dehydration, urolithiasis, renal injury and infectious and vector-borne diseases. Adding to the potential effect on disease pathogenesis, many patients with urological diseases undergo high-tech, resource-intensive interventions, such as robotic surgery, and entail intensive longitudinal assessments over many years. These features incur a considerable carbon footprint, generate substantial waste, and can introduce vulnerabilities to climate-related weather events. Links exist between planetary health (the health of humans and the natural systems that support our health), climate change and urological disease and urological care providers face many challenges in the era of anthropogenic climate change. The next steps and priorities for research, management, and health care delivery include identification and prioritization of health care delivery strategies to minimize waste and carbon emissions, while supporting climate resilience. Examples include supporting telemedicine, limiting low-value care, and building resilience to minimize impacts of climate-related disasters to prepare for the challenges ahead.

Evaluating the ingress of total polycyclic aromatic hydrocarbons (PAHs) specifically naphthalene through firefighter hoods and base layers

Structural firefighters are exposed to an array of polycyclic aromatic hydrocarbons (PAHs) as a result of incomplete combustion of both synthetic and natural materials. PAHs are found in both the particulate and vapor phases in the firefighting environment and are significantly associated with acute and chronic diseases, including cancer. Using a fireground exposure simulator (FES) and standing mannequins dressed in four different firefighter personal protective equipment (PPE) conditions, each with varying levels of protective hood interface and particulate-blocking features, the efficacy of the hoods was assessed against the ingress of PAHs (specifically, naphthalene). The authors also explored the effectiveness of a 100% cotton turtleneck at further attenuating the amount of naphthalene reaching the surface of the mannequin's neck. Air samples were collected at the breathing zone, abdomen, and thigh heights from the 6 ft-2 in mannequins used in this study. Naphthalene was the most abundant PAH (55% of the total PAH concentrations) in the FES and existed primarily in the vapor phase (92% vapor in the breathing zone). Additionally, bulk base layer and under the base layer polytetrafluoroethylene (PTFE) filter samples (used as skin surrogates) were collected from the neck region of the mannequins and analyzed for PAHs. A larger percentage of naphthalene was collected on the filter under the traditional knit hoods than on the cotton base layer, suggesting a small protective effect of the base layer against solid-phase naphthalene. Previous studies investigating naphthalene by employing air sampling under PPE have found a larger protective effect of base layers against the ingress of naphthalene vapor. PAHs that exist primarily as particulate in the fire environment were largely not detected on the base layers or PTFE filters under the gear. Further research is needed that involves more sensitive methods and non-static human subjects.

Occupational exposures of firefighting and prostate cancer risk in the Norwegian Fire Departments Cohort

OBJECTIVES

Excess incidence of prostate cancer (PC) is frequently observed among firefighters; however, the association with specific occupational exposures of firefighting, as well as the influence of a medical surveillance bias, remains unclear. Our aim was to study PC risk within a firefighter cohort, applying indicators of exposures.

METHODS

We used indicators of various firefighting exposures to examine PC risk among men in the Norwegian Fire Departments Cohort (N=4251). Incident PC cases, including clinical characteristics, were obtained from the Cancer Registry of Norway (1960-2021). Cox regression was used to estimate hazard ratios (HR) by cumulative exposure in tertiles (reference: lowest) for all, aggressive, and indolent PC, with adjustment for age and birth cohort. The cumulative incidence of PC across birth cohorts and diagnostic periods was examined.

RESULTS

No clear associations emerged for any of the exposure indicators, although we observed an HR of 1.31 [95% confidence interval (CI) 0.63-2.72] for aggressive PC in the highest tertile of fire exposure score and 1.31 (95% CI 0.60-2.89) for indolent PC in the highest tertile of inhalation score. Assessment of cumulative incidence demonstrated a greater number of diagnoses at younger ages after 1990, particularly for indolent and unclassifiable PC.

CONCLUSIONS

We found little support for an association between firefighting exposures and PC risk. However, our study had few cases in analyses by clinical stage. Challenges in studies of firefighters' PC risk remain, including difficulties in exposure characterization and the unclear magnitude of a medical surveillance bias.

[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.

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.

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.

Firefighter- and Fire Department-Level Barriers and Promoters of Physical Activity and Fitness Among Volunteer Firefighters: A Qualitative Study Using Semistructured Interviews

OBJECTIVE

To describe volunteer firefighters' perspectives on how firefighter- and fire department-level factors influence their physical activity and fitness.

METHODS

Firefighters (n = 28) were interviewed, stratified by their years of firefighting, using an interview guide. Thematic analysis and systematic coding were used to analyze the interview transcripts.

RESULTS

Five themes were identified: (1) health and firefighting performance, (2) firefighter time and availability, (3) responsibility of the fire department to support volunteer members' physical fitness, (4) fire training drills as a form of functional physical activity, and (5) fitness initiatives at the department. Interviewing by years of experience showed varied perspectives that converged toward similar conclusions.

CONCLUSIONS

Incorporating fitness discussions into department meetings and trainings and identifying fitness advocates within the department may contribute to overcoming barriers to physical fitness among volunteer firefighters.

Assessment of Polycyclic Aromatic Hydrocarbon Exposure in Trainee Firefighters Using PAH CALUX Bioassay

This work investigated the application of a reporter gene bioassay in assessing polycyclic aromatic hydrocarbon (PAH) exposure in trainee firefighters. In the PAH CALUX bioassay, the PAH-induced activation of the aryl hydrocarbon receptor in a reporter cell line is recorded by increased luminescence. A repeated measurement study was performed, collecting urine and skin wipe samples at two baseline sessions (spring and autumn) and after three firefighting sessions: one with wood fuel, one with gas fuel, and one without fire. The bioassay response was expressed as benzo[a]pyrene equivalents, which was compared to levels of 16 EPA criteria PAHs in skin wipe samples and 8 hydroxylated PAHs (OH-PAHs) in urine samples quantified by chromatography-tandem mass spectrometry techniques. Benzo[a]pyrene equivalents and PAH levels in skin wipes indicated larger exposure to PAHs during the wood session compared to the other sessions. The urine bioassay showed non-significant effect sizes after all sessions, whereas the chemical analysis showed increased OH-PAH levels after the gas session. The non-significant changes observed for the session without fire suggest a negligible exposure from contaminated gear. In conclusion, the bioassay response for skin wipes shows that trainee firefighters were exposed to higher levels of potentially toxic PAHs during the wood fire training session.

Cardiorespiratory Fitness Is Not Associated with Cardiovascular Disease Risk in Firefighters: A Cross-Sectional Study in South African Firefighters

Cardiovascular disease (CVD) risk factors are frequently reported among firefighters, yet no studies have compared these factors between male and female firefighters, specifically from a low- to middle-income country (LMIC). This study aimed to determine the prevalence of CVD risk factors and their relationship with cardiorespiratory fitness (VO2max) in 254 active career firefighters (mean age: 42.6 ± 7.8 years). The assessments included anthropometry, blood pressure, blood glucose, cholesterol, triglycerides, and VO2max. The results indicated that 48.0% and 51.8% of females and males were pre-hypertensive, respectively. Hypertension was identified in 15.8% of the firefighters. According to body mass index (BMI), 37.3% of males and 25% of females were found to be overweight, while an additional 44.9% of males and 45.7% of females were classified as obese. Only 17.3% of males and 18.2% of females were found to be of normal weight. These findings were corroborated by categories of central obesity using waist circumference (WC), which were 47.7% for males and 41.6% for females. Low HDL-C was found in 95.2% of males and 86.4% of females, with 28.3% of males also having elevated triglyceride levels (TG). VO2max was "excellent" in 48.8% of males and 12.6% of females, though it had no significant association with most CVD risk factors. The only notable link was a small correlation between VO2max and triglycerides (r = -0.215; p = 0.001). These findings suggest that while cardiorespiratory fitness may have no impact, additional factors likely contribute to the cardiovascular health of firefighters, necessitating the need for comprehensive health and fitness programmes.

Cancer incidence in a cohort of Danish firefighters: An extended long-term follow-up 1968-2021

OBJECTIVES

To update and extend the examination of cancer incidence in a cohort of Danish firefighters, now adding 7 years of follow-up and 2766 additional firefighters. The primary focus was directed toward cancer sites that recently contributed to the hazard evaluation conducted by the International Agency for Research on Cancer (IARC).

METHODS

The updated cohort consisted of 11,827 male Danish firefighters who were followed up for cancer from 1968 to 2021. Cohort cancer morbidity was compared with a working population reference group, and standardized incidence ratios (SIR) were used for estimation of relative risks, along with 95% confidence intervals (95% CI).

RESULTS

Among full-time firefighters, SIR of skin melanoma was 1.30 (95% CI: 1.02-1.66), and SIR = 1.37 (95% CI: 1.02-1.85) for over 5 years of employment. Slightly positive associations were also observed for cancer of the urinary bladder (SIR = 1.16; 95% CI: 0.93-1.45), prostate (SIR = 1.11; 95% CI: 0.97-1.28), and testis (SIR = 1.11; 95% CI: 0.75-1.63).

CONCLUSIONS

This updated study provides evidence indicating an elevated risk of skin melanoma in firefighters. Consistent with IARC's evaluation, we also identified positive associations for urinary bladder, prostate, and testis cancer. In contrast, our findings did not suggest an increased risk of colon cancer, non-Hodgkin lymphoma, and mesothelioma. The latter may be due to small numbers in our still relatively young cohort. Continuous follow-up for cancer in firefighters is warranted, including assessment of influence from surveillance bias.

Exploring the interplay between circadian rhythms and prostate cancer: insights into androgen receptor signaling and therapeutic opportunities

Circadian rhythm disruption is closely related to increased incidence of prostate cancer. Incorporating circadian rhythms into the study of prostate cancer pathogenesis can provide a more comprehensive understanding of the causes of cancer and offer new options for precise treatment. Therefore, this article comprehensively summarizes the epidemiology of prostate cancer, expounds the contradictory relationship between circadian rhythm disorders and prostate cancer risk, and elucidates the relationship between circadian rhythm regulators and the incidence of prostate cancer. Importantly, this article also focuses on the correlation between circadian rhythms and androgen receptor signaling pathways, as well as the applicability of time therapy in prostate cancer. This may prove significant in enhancing the clinical treatment of prostate cancer.

Perceptions of Preventable Cancer Burden Among US-Based Firefighters: A Mixed Methods Cross-Sectional Study

OBJECTIVE

Characterize experiences with cancer and perceptions of the preventable cancer burden attributable to diet among firefighters.

DESIGN

A cross-sectional survey was distributed to assess cancer history and perceptions of cancer.

SETTING

US.

PARTICIPANTS

US-based firefighters.

MAIN OUTCOME MEASURE(S)

History of cancer, perceptions of cancer, and perceptions of diet as a means to prevent cancer.

ANALYSIS

Descriptive statistics and use of the Behaviour Change Technique Taxonomy v1 (BCTTv1) to evaluate qualitative responses.

RESULTS

A total of 471 firefighters participated. Nearly half (48.4%) voiced they strongly agreed that they were at risk for cancer, whereas 44.6% agreed that changing diet could decrease cancer risk. The most common BCTTv1 codes focused on types of education, including "Instruction on how to perform the behavior" (45.1%, n = 189), followed by those centered on behavior execution (eg, "Action planning" [24.8%, n = 104]). Qualitatively, many were concerned about misinformation.

CONCLUSIONS AND IMPLICATIONS

Firefighters acknowledge the role of diet in cancer risk and have a desire for knowledge and behavioral support (eg, goal setting) that includes an emphasis on evidence and tackling misinformation. This information should serve as the basis of future interventions that target diet.

The Influence of Sex and/or Gender on the Occurrence of Colorectal Cancer in the General Population in Developed Countries: A Scoping Review

Objective: Gender as the "sociocultural role of sex" is underrepresented in colorectal cancer incidence studies, potentially resulting in underestimated risk factors' consequences and inequalities men/women. We aim to explore how literature focusing on differences between men and women in the incidence of colorectal cancer interprets these differences: through sex- or gender-related mechanisms, or both? Methods: We conducted a scoping review using PubMed and Google Scholar. We categorized studies based on their definitions of sex and/or gender variables. Results: We reviewed 99 studies, with 7 articles included in the analysis. All observed differences between men and women. Six articles examined colorectal cancer incidence by gender, but only 2 used the term "gender" to define exposure. One article defined its "sex" exposure variable as gender-related mechanisms, and two articles used "sex" and "gender" interchangeably to explain these inequalities. Gender mechanisms frequently manifest through health behaviors. Conclusion: Our results underscore the need for an explicit conceptual framework to disentangle sex and/or gender mechanisms in colorectal cancer incidence. Such understanding would contribute to the reduction and prevention of social health inequalities.

Temporal changes in cumulative mortality risks of cancer, by occupation, in the working population of Japan from 1995 to 2020: a benchmark for radiation risk comparison

The purpose of this study was to provide benchmark data for discussing the tolerability of cancer risk associated with occupational radiation exposure. It focused on differences in cancer mortality risk by occupation among Japan's working population and examined baseline cancer mortality risks and its variations from 1995 through 2020. Data were collected every five years from national vital statistics sources. By focusing on the same types of cancer among radiation induced effects, cumulative mortality risks were calculated for colorectal, lung, and breast cancer (females only) for those aged 15-74. The average cumulative mortality risk for the working population in Japan has decreased by 30%-60% over the past 25 years. Service workers and male managers were at an average risk, among all workers, while clerical workers and transportation and manufacturing workers had about half the average risk. The risks were higher for professionals and female managers, about 1.5-2 times the average for professionals and up to 5 times the average for female managers. The decrease in the average cancer mortality risk in the working population as a baseline suggests that risk tolerance in society might have changed over time. Since differences in mortality by occupation were confirmed, the usefulness of occupational data as a benchmark needs further investigation, as high-risk/low-risk occupations vary by country and region. The results of this study contribute to put radiation risks into perspective with the background risk of cancer.

Risk factors for prostate cancer: An umbrella review of prospective observational studies and mendelian randomization analyses

BACKGROUND

The incidence of prostate cancer is increasing in older males globally. Age, ethnicity, and family history are identified as the well-known risk factors for prostate cancer, but few modifiable factors have been firmly established. The objective of this study was to identify and evaluate various factors modifying the risk of prostate cancer reported in meta-analyses of prospective observational studies and mendelian randomization (MR) analyses.

METHODS AND FINDINGS

We searched PubMed, Embase, and Web of Science from the inception to January 10, 2022, updated on September 9, 2023, to identify meta-analyses and MR studies on prostate cancer. Eligibility criteria for meta-analyses were (1) meta-analyses including prospective observational studies or studies that declared outcome-free at baseline; (2) evaluating the factors of any category associated with prostate cancer incidence; and (3) providing effect estimates for further data synthesis. Similar criteria were applied to MR studies. Meta-analysis was repeated using the random-effects inverse-variance model with DerSimonian-Laird method. Quality assessment was then conducted for included meta-analyses using AMSTAR-2 tool and for MR studies using STROBE-MR and assumption evaluation. Subsequent evidence grading criteria for significant associations in meta-analyses contained sample size, P values and 95% confidence intervals, 95% prediction intervals, heterogeneity, and publication bias, assigning 4 evidence grades (convincing, highly suggestive, suggestive, or weak). Significant associations in MR studies were graded as robust, probable, suggestive, or insufficient considering P values and concordance of effect directions. Finally, 92 selected from 411 meta-analyses and 64 selected from 118 MR studies were included after excluding the overlapping and outdated studies which were published earlier and contained fewer participants or fewer instrument variables for the same exposure. In total, 123 observational associations (45 significant and 78 null) and 145 causal associations (55 significant and 90 null) were categorized into lifestyle; diet and nutrition; anthropometric indices; biomarkers; clinical variables, diseases, and treatments; and environmental factors. Concerning evidence grading on significant associations, there were 5 highly suggestive, 36 suggestive, and 4 weak associations in meta-analyses, and 10 robust, 24 probable, 4 suggestive, and 17 insufficient causal associations in MR studies. Twenty-six overlapping factors between meta-analyses and MR studies were identified, with consistent significant effects found for physical activity (PA) (occupational PA in meta: OR = 0.87, 95% CI: 0.80, 0.94; accelerator-measured PA in MR: OR = 0.49, 95% CI: 0.33, 0.72), height (meta: OR = 1.09, 95% CI: 1.06, 1.12; MR: OR = 1.07, 95% CI: 1.01, 1.15, for aggressive prostate cancer), and smoking (current smoking in meta: OR = 0.74, 95% CI: 0.68, 0.80; smoking initiation in MR: OR = 0.91, 95% CI: 0.86, 0.97). Methodological limitation is that the evidence grading criteria could be expanded by considering more indices.

CONCLUSIONS

In this large-scale study, we summarized the associations of various factors with prostate cancer risk and provided comparisons between observational associations by meta-analysis and genetically estimated causality by MR analyses. In the absence of convincing overlapping evidence based on the existing literature, no robust associations were identified, but some effects were observed for height, physical activity, and smoking.

Cancer-Related Behavioral Risk Factors Among Volunteer and Career Firefighters Enrolled in the Cancer Assessment and Prevention Study (CAPS) and the Fire Fighter Cancer Cohort Study (FFCCS)

Although nearly two-thirds of U.S. firefighters serve as volunteers, they are rarely included in studies of firefighters' health. The Firefighter Cancer Assessment and Prevention Study (CAPS), a research component of the Fire Fighter Cancer Cohort Study (FFCCS), has enrolled over 600 U.S. volunteer firefighters to help address this gap. This study found a greater prevalence of cancer-related health behaviors among volunteers compared to career firefighters. These behaviors included cigarette smoking, heavy alcohol use, and obesity. While the differences in behaviors varied between U.S. states, all state-level prevalences were higher among volunteer firefighters than career firefighters. The findings of this study support the need to provide volunteer firefighters with overall and targeted health promotion and cancer prevention programs.

Firefighting, per- and polyfluoroalkyl substances, and DNA methylation of genes associated with prostate cancer risk

Prostate cancer is the leading incident cancer among men in the United States. Firefighters are diagnosed with this disease at a rate 1.21 times higher than the average population. This increased risk may result from occupational exposures to many toxicants, including per- and polyfluoroalkyl substances (PFAS). This study assessed the association between firefighting as an occupation in general or PFAS serum levels, with DNA methylation. Only genomic regions previously linked to prostate cancer risk were selected for analysis: GSTP1, Alu repetitive elements, and the 8q24 chromosomal region. There were 444 male firefighters included in this study, with some analyses being conducted on fewer participants due to missingness. Statistical models were used to test associations between exposures and DNA methylation at CpG sites in the selected genomic regions. Exposure variables included proxies of cumulative firefighting exposures (incumbent versus academy status and years of firefighting experience) and biomarkers of PFAS exposures (serum concentrations of 9 PFAS). Proxies of cumulative exposures were associated with DNA methylation at 15 CpG sites and one region located within FAM83A (q-value <0.1). SbPFOA was associated with 19 CpG sites (q < 0.1), but due to low detection rates, this PFAS was modeled as detected versus not detected in serum. Overall, there is evidence that firefighting experience is associated with differential DNA methylation in prostate cancer risk loci, but this study did not find evidence that these differences are due to PFAS exposures specifically.

Cancer Risks among Emergency Medical Services Workers in Ontario, Canada

OBJECTIVES

Emergency medical services workers, such as paramedics, provide important emergency care and may be exposed to potential carcinogens while working. Few studies have examined the risk of cancer among paramedics demonstrating an important knowledge gap in existing literature. This study aimed to investigate cancer risks among paramedics in a large cohort of Ontario workers.

METHODS

Paramedics were identified in the Occupational Disease Surveillance System (ODSS) from 1996 to 2019. The ODSS was established by linking lost-time worker's compensation claims to administrative health data, including the Ontario Cancer Registry to identify incident cases of cancer. Cox-proportional hazard models were used to calculate age and sex-adjusted hazard ratios and 95% confidence intervals to estimate the risk of cancer among paramedics compared to all other workers in the ODSS.

RESULTS

A total of 7240 paramedics were identified, with just over half of the paramedics identifying as male similar to the overall ODSS cohort. Paramedics had a statistically significant elevated risk of any cancer (HR 1.19, 95% CI 1.06-1.34), and elevated risks for melanoma (HR 2.18, 95% CI 1.46-3.26) and prostate cancer (HR 1.73, 95% CI 1.34-2.22). Paramedics had a statistically significant reduced risk for lung cancer (HR 0.48, 95% CI 0.28-0.83). Findings were similar to cancer risks identified in firefighters and police in the same cohort.

CONCLUSIONS

This study contributes valuable findings to understanding cancer risks among paramedics and further supports the existing evidence on the increased risk of cancer among emergency medical services workers. We have observed some similar results for firefighters and police, which may be explained by similar exposures, including vehicle exhaust, shiftwork, and intermittent solar radiation. This can lead to a better understanding of carcinogens and other exposures among paramedics and inform cancer prevention strategies.

Biomonitoring of polycyclic aromatic hydrocarbons in firefighters at fire training facilities and in employees at respiratory protection and hose workshops

Introduction

Polycyclic aromatic hydrocarbons (PAHs) are carcinogenic to humans and are formed by incomplete combustion. PAHs are always present during firefighting operations, and fire department members can be exposed to them in the workplace.

Methods

In this study, we analyzed 1-hydroxypyrene (1-OHP) in 36 urine samples from nine firefighters, collected before and after fire training sessions, and 32 urine samples from eight employees at respiratory protection and hose workshops. To assess breakthrough PAH exposure through personal protective equipment and potential dermal uptake, some of the workshop employees wore cotton garments under their regular workwear. Cotton samples were then examined for the presence of 17 semi-volatile and low-volatility PAHs.

Results

After firefighting exercises, we observed approximately a fivefold increase in mean 1-OHP concentrations in samples from firefighters, from 0.24 μg/L to 1.17 μg/L (maximum: 5.31 μg/L). In contrast, 1-OHP levels in workshop employees were found to be low, with the majority of urine samples yielding concentrations below the limit of quantification (LOQ: 0.05 μg/L, maximum: 0.11 μg/L). Similarly, low PAH levels were found on the workshop employees' cotton undergarments, with maximum concentrations of 250 and 205 ng/g for pyrene and benzo[a]pyrene, respectively.

Discussion

In conclusion, significant increases in 1-OHP in urine were observed in firefighters after training sessions, whereas work-related exposure remained low among workshop employees.

Occupational exposures of firefighting and urinary tract cancer risk among men in the Norwegian Fire Departments Cohort

OBJECTIVES

Increased risks of bladder cancer and mesothelioma were the strongest evidence for the recent reclassification of firefighting as carcinogenic (Group 1) by the International Agency for Research on Cancer. Our study aim was to develop indicators for specific firefighting exposures and examine associations with urinary tract cancer (UTC), including bladder cancer.

METHODS

We developed indicators for exposure from employment at a fire department or in firefighting jobs, to fire and smoke, and to diesel exhaust for men in the Norwegian Fire Departments Cohort (n=4250). Incident UTC cases were obtained from the Cancer Registry of Norway (1960-2021). Poisson regression was used to estimate incidence rate ratios (IRR) with cumulative exposures grouped into tertiles (reference: lowest exposed tertile) with 0-year, 10-year and 15-year lagging of exposures.

RESULTS

During 125 090 person-years of follow-up, there were 76 cases of UTC. IRRs were mostly non-significantly increased in the middle tertile and at or below 1 in the highest tertile for total duration of employment, number of fires attended and fire exposure score with and without lags. In the middle tertile for diesel exhaust exposure, UTC risk was elevated over twofold with 10-year (IRR 2.27, 95% CI 1.22 to 4.20) and 15- year (2.21, 1.18 to 4.16) lags, and near 1 in the highest tertile. Findings for bladder cancer were similar to those for UTC.

CONCLUSIONS

Dose-response associations between the exposure indicators and UTC were not observed. Future studies using the indicators with more cases are needed.

Prevalence and predictors of skin cancer screening among a sample of US volunteer firefighters

BACKGROUND

Firefighters have a higher risk of melanoma incidence and mortality compared to the general population. In the United States (US), the National Fire Protection Association recommends all firefighters receive annual skin cancer screening through visual skin examination by a clinician. However, there is limited information on skin cancer screening practices among volunteer firefighters who comprise two-thirds of the US fire service.

METHODS

This cross-sectional study of 552 US volunteer firefighters estimated the prevalence of skin cancer screening and evaluated associations with their fire service experience, demographics, sun protection practices, and cancer risk perception.

RESULTS

The prevalence of receiving skin cancer screening among volunteer firefighters was 26.1% (95% confidence interval [CI]: 22.4, 29.8). The odds of being screened for skin cancer, compared to not being screened, were twice as high for firefighters who used sunscreen (odds ratio [OR]: 2.35, 95% CI: 1.48, 3.73) and who perceived their skin likely to burn with prolonged sun exposure (OR: 1.81, 95% CI: 1.10, 3.00). Older age, some college education, and family history of skin cancer were also positively associated with skin cancer screening. A positive exposure-response relationship was observed between more monthly firefighting calls and receiving screening. Cancer risk perception was not associated with screening.

CONCLUSION

To our knowledge, this is the first large study to assess skin cancer screening among US volunteer firefighters. Our findings suggest gaps in skin cancer prevention efforts in the volunteer fire service. Additional assessment of skin cancer prevention practices within volunteer fire departments could help address these gaps.