Extreme occupational heat exposure is associated with elevated haematological and inflammatory markers in Fire Service Instructors

Abstract

Fire Service Instructors (FSIs) experience ∼10 times more fire exposures than firefighters (FFs), and the increased physiological stress from this potentially puts them at risk of ill health and future cardiac events. The aim of the study was to establish whether FSIs exhibit elevated biomarkers associated with cardiac event risk, identify whether FSIs experience systemic inflammation linked to the frequency of fire exposure and evaluate a proposed exposure limit of nine exposures per month. Blood samples were collected from 110 Fire Service personnel (mean ± SD, age,44 ± 7 years; height, 178.1 ± 7.1 cm; and body mass, 84.3 ± 12.0 kg; FSIs n = 53 and FFs n = 57) for biomarker analysis. Work history details were collected from all participants. Participants with biomarker concentrations above healthy reference ranges were classified as being 'at risk'. The neutrophil-to-lymphocyte ratio, platelet count, cardiac troponin T, interleukin (IL)-6, IL-1 , C-reactive protein and immunoglobulin G were greater in FSIs than in FFs (P < 0.05). Multiple regression analysis revealed that 18.8% of IL-6, 24.9% of IL-1 , 29.2% of C-reactive protein and 10.9% of immunoglobulin G variance could be explained by the number of exposures to heat per month. Odds ratios revealed that those FSIs above the nine per month exposure limit were six to 12 times more likely to be classified as 'at risk' and were 16 times more likely to experience symptoms of ill health. Increased cytokine levels suggest that FSIs experience systemic inflammation, which is related to symptoms of ill health. We propose that an exposure limit could reduce the prevalence of these biomarker risk factors and ill health.

Higher Temperatures, Higher Solar Radiation, and Less Humidity Is Associated With Poor Clinical and Laboratory Outcomes in COVID-19 Patients

“…Elevated ambient temperatures can affect the cardiocirculatory and hormonal systems, resulting in changes in neutrophil and monocyte cell trafficking (41). The neutrophil-to-lymphocyte ratio, interleukin (IL)-6, IL-1β, and CRP were higher in persons exposed more frequently to heat per month, which might predispose to systemic inflammation (42). Long-term heat exposure was found to enhance chemokines to recruitment neutrophils to the lungs, leading to an increased risk of respiratory illnesses (43).…”

Are Inflammatory Markers an Indicator of Exposure or Effect in Firefighters Fighting a Devastating Wildfire? Follow-up of a Cohort in Alberta, Canada

“…The study has limitations. The negative relation between estimated PM 2.5 and inflammatory markers in plasma from the blood draw 15–19 days from the start of the fire was unexpected and may indicate that these early markers are reflecting, in part, other factors known to reflect cytokine concentrations such as physical exercise ( Pedersen et al , 2001 ) or heat stress ( Wright-Beatty et al , 2014 ; Watkins et al , 2021 ) rather than simply PM 2.5 exposure. Interpretation was complicated by the non-linear relationship between the intensity of particulate exposure and time since last exposure, which limited also the interpretation of urinary 1-hydroxypyrene in this sample ( Cherry et al , 2019 ).…”

“… Gianniou et al (2016) , compared concentrations of markers including IL-8, TNF-α, and vascular endothelial cell growth factor (VEGF), all of which were higher in professional firefighters than trainees. Watkins et al (2021) found that higher IL-6 and IL-1β related to the number of fire exposures in the last month among fire service instructors. Following the collapse of the World Trade Center on 11 September 2001, serum samples were collected from New York City firefighters and analysed for inflammatory markers for cases and referents drawn from a cohort of 1720 undergoing subspecialty pulmonary evaluation (SPE) ( Nolan et al , 2012 ).…”

Lifestyle and environmental factors may induce airway and systemic inflammation in firefighters

“…Another group that is regularly exposed to fire scenarios, and at the same time not directly related to firefighting, are fire service instructors (Watkins et al 2021a ). Fire service instructors, who are responsible for conducting training reported an average of around 13 fire exposures per month, compared to active firefighters with an average of 1 fire over the same period (Watkins et al 2018 ).…”