Extreme occupational is associated with elevated haematological markers in Instructors

: Fire Service Instructors (FSI) experience ~10 times more fire exposures than firefighters (FF), the increased physiological stress from this potentially puts them at risk of ill health and future cardiac events. This study aimed to establish whether FSI exhibit elevated biomarkers associated with cardiac event risk, identify if FSI experience systemic inflammation linked to fire exposure frequencies and evaluate a proposed exposure limit of 9 per month. Blood samples were collected from 110 Fire Service personnel (age: 44 {plus minus} 7 yrs; height: 178.1 {plus minus} 7.1 cm; body mass: 84.3 {plus minus} 12.0 kg, FSI n = 53, FF n = 57) for biomarker analysis. Work history details were collected from all participants. Participants with biomarker concentrations above healthy reference ranges were classified as "at risk". Neutrophil/lymphocyte ratio, platelet count, cardiac troponin T, interleukin-6 (IL-6), interleukin-1β (IL-1β), Multiple regression 18.8% of IL-6, 24.9% of IL-1β, 29.2% of CRP, and 10.9% of IgG variance could be explained by number of heat exposures per month. Odds ratios revealed that those above the 9 per month exposure limit were 6-12 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 FSI 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. New Findings: Fire service instructors are frequently exposed to live fire scenarios, representing the most extreme chronic occupational heat exposure. These individuals report a series of unique health issues. This study seeks to identify if the number of exposures completed are associated with inflammatory and immunological markers and symptoms of ill health. Fire service instructors exhibit greater levels of inflammatory markers in comparison to firefighters. Fire exposure numbers are positively related with the prevalence of ill health and inflammation. Implementation of a proposed 9 exposure limit per month may be appropriate to minimise health issues. ABSTRACT Fire Service Instructors (FSI) experience ~10 times more fire exposures than firefighters (FF), the increased physiological stress from this potentially puts them at risk of ill health and future cardiac events. This study 47 aimed to establish whether FSI exhibit elevated biomarkers associated with cardiac event risk, identify if FSI 48 experience systemic inflammation linked to fire exposure frequencies and evaluate a proposed exposure limit of 49 9 per month. Blood samples were collected from 110 Fire Service personnel (age: 44 ± 7 yrs; height: 178.1 ± 7.1 50 cm; body mass: 84.3 ± 12.0 kg, FSI n = 53, FF n = 57) for biomarker analysis. Work history details were 51 collected from all participants. Participants with biomarker concentrations above healthy reference ranges were 52 classified as “at risk”. Neutrophil/lymphocyte ratio, platelet count, cardiac troponin T, interleukin-6 (IL-6), 53 interleukin-1β (IL-1β), immunoglobulin G (IgG) and C reactive protein (CRP) were greater in FSI than FF 54 ( p <0.05). Multiple regression analysis revealed 18.8% of IL-6, 24.9% of IL-1β, 29.2% of CRP, and 10.9% of 55 IgG variance could be explained by number of heat exposures per month. Odds ratios revealed that those above 56 the 9 per month exposure limit were 6-12 times more likely to be classified as “at risk” and were 16 times more 57 likely to experience symptoms of ill health. Increased cytokine levels suggest FSI experience systemic 58 inflammation, which is related to symptoms of ill health. We propose that an exposure limit could reduce the 59 prevalence of these biomarker risk factors and ill health.