Skip to main content
OpenTrials
Completed

NCT Number: NCT05753254

Effect on Markers of Cardiovascular, Reproductive and Cancer Risk From Firefighting Training

Epidemiological studies based on Danish registries have observed that Danish male firefighters have more cardiovascular disease, infertility diagnose and a trend to increased risk of cancer than other Danish employed males. Firefighting activities include a combination of stressors such as strenuous work under heat, smoke and soot known to be able to affect cardiovascular and reproductive health, with smoke and soot also being known to increase the risk of cancer.

The training facilities of real-fire extinguishing exercises in Denmark operate using wood or natural gas fire, which will have differential gradients of smoke, soot and possibly heat. The investigators will use different training conditions to create gradients of the different stressors and investigate health effects thereof. With this approach, the investigators expect to be able to evaluate the individual contribution of the different stressors in markers of cardiovascular, cancer and reproductive health risk. The project will include approx. 35 young conscript participants on a firefighting course, followed in four sessions, three firefighting training sessions under different fire conditions (no fire, wood fire and gas fire) and one control scenario.

Completed

Looking for future studies?

Notify Me

Key information

Conditions

Reactive Hyperemia Cardiovascular Diseases DNA Strand Breaks Heart Rate Variability Heat Stress Heat Stress Disorders Hyperemia Micro RNA Oxidative Stress Vascular Diseases Wounds and Injuries

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

The National Research Centre for the Working Environment, Copenhagen, Denmark

Loading trial locations.

About this study

The study methodology is based on a crossover design on firefighting training under different conditions, with characterization of exposure and assessment of cardiovascular, cancer and reproductive effect biomarkers. The study will be performed in cooperation with the Danish Emergency Management Agency.

The study will have one baseline session, while conscripts are in a classroom, and three sessions of firefighting-related exercises under different fire conditions, used currently in firefighting training programs in Denmark. The three firefighting training sessions will be controlled for equivalent work exercise using full protective gear and under different ambient conditions of firefighting training:

  • Firefighting equivalent work (no fire), with exercises performed in a clean environment, without fire (no ambient temperature, soot or smoke). This type of exercise precedes or complements the training under real fire conditions.
  • Firefighting under wood fire (wood fire), with exposure to ambient heat, smoke and soot. This is the most common training scenario used by Danish Emergency Management Agency training centres.
  • Firefighting under gas fire (gas fire), with exposure to ambient heat, and expectably less smoke and soot than with wood fire. These conditions are used in some Danish training centres, with logistical advantages (ease of turning or putting out the fire and managing the fire fuel) and unknown effect relating to exposure prevention (smoke and soot).

The order of the firefighting sessions will be as randomized as possible, and according to a selection of three sequence order options (no-wood-gas; wood-gas-no and gas-wood-no). Each campaign (corresponding to each rescue course) would desirably have one of these session sequences. It is not possible to blind the participants to the different scenarios, neither the field staff, but all the samples will be blinded for the subsequent laboratory analysis. The training sessions will have 1-3 weeks in between (accordingly with programmatic educational course schemes).

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

The participants will be volunteers (both males and females) recruited among conscripts in training in a desirable involved group up to 35 individuals.

Inclusion criteria

  • legally competent,
  • conscript subjects following a Rescue Specialist Educational course

Exclusion criteria

  • current smoking status,
  • pregnancy,
  • on prescribed medication,
  • body mass index (BMI) bellow 19 or over 30,
  • alcohol or drug abuse.

Treatment and study plan

Firefighting training exercises with no fire

Other

The participants will be performing firefighting equivalent work in a clean environment, without fire (no ambient temperature, soot or smoke).

Firefighting training exercises under wood fire

Other

The participants will be in teams performing pre-defined tasks (knocking down the fire, moving heavy objects, and searching and rescuing metal stand in models), under wood fire conditions.

Firefighting training exercises under gas fire

Other

The participants will be in teams performing pre-defined tasks (knocking down the fire, moving heavy objects, and searching and rescuing metal stand in models), under gas fire conditions.

Primary outcomes

  1. Change in reactive hyperemia index - afternoon

    Time frame: Baseline afternoon measurement, afternoon measurement immediately after firefighting without fire, afternoon measurement immediately after firefighting under wood fire and afternoon measurements immediately after firefighting under gas fire

    Reactive hyperemia index (RHI) measured with the device EndoPAT 2000. A reactive hyperemia is induced by a blood cuff on the upper arm and the peripheral vasodilation response is assessed in the small digital vessels of a fingertip with a portable device connected to a computer, with RHI determined by an algorithm from the device, with lower index values corresponding to a worsen situation.

  2. Change in reactive hyperemia index - morning

    Time frame: Baseline morning measurement, morning measurement in subsequent day after firefighting without fire, morning measurement in subsequent day after firefighting under wood fire and morning measurement in subsequent day after firefighting under gas fire

    Reactive hyperemia index (RHI) measured with the device EndoPAT 2000. A reactive hyperemia is induced by a blood cuff on the upper arm and the peripheral vasodilation response is assessed in the small digital vessels of a fingertip with a portable device connected to a computer, with RHI determined by an algorithm from the device, with lower index values corresponding to a worsen situation.

  3. Change in Heart Rate Variability pNN50 at rest - afternoon

    Time frame: Baseline afternoon measurement, afternoon measurement immediately after firefighting without fire, afternoon measurement immediately after firefighting under wood fire and afternoon measurements immediately after firefighting under gas fire

    Heart rate variability (HRV) measured with the device EndoPAT 2000. The HRV is calculated using the initial 5.5 complete minutes before the cuff is applied. pNN50 is the proportion of successive NN intervals differing by more than 50 milliseconds divided by the total number of N intervals (given in percentage).

  4. Change in Heart Rate Variability pNN50 at rest - morning

    Time frame: Baseline morning measurement, morning measurement in subsequent day after firefighting without fire, morning measurement in subsequent day after firefighting under wood fire and morning measurement in subsequent day after firefighting under gas fire

    Heart rate variability (HRV) measured with the device EndoPAT 2000. The HRV is calculated using the initial 5.5 complete minutes before the cuff is applied. pNN50 is the proportion of successive NN intervals differing by more than 50 milliseconds divided by the total number of N intervals (given in percentage).

  5. Change in Heart Rate Variability RMSSD at rest - afternoon

    Time frame: Baseline afternoon measurement, afternoon measurement immediately after firefighting without fire, afternoon measurement immediately after firefighting under wood fire and afternoon measurements immediately after firefighting under gas fire

    Heart rate variability (HRV) measured with the device EndoPAT 2000. The HRV is calculated using the initial 5.5 complete minutes before the cuff is applied. RMSSD is the square root of the mean squared differences of successive NN intervals (given in milliseconds)

  6. Change in Heart Rate Variability RMSSD at rest - morning

    Time frame: Baseline morning measurement, morning measurement in subsequent day after firefighting without fire, morning measurement in subsequent day after firefighting under wood fire and morning measurement in subsequent day after firefighting under gas fire

    Heart rate variability (HRV) measured with the device EndoPAT 2000. The HRV is calculated using the initial 5.5 complete minutes before the cuff is applied. RMSSD is the square root of the mean squared differences of successive NN intervals (given in milliseconds)

  7. Change in Heart Rate Variability ratio LF/HF at rest - afternoon

    Time frame: Baseline afternoon measurement, afternoon measurement immediately after firefighting without fire, afternoon measurement immediately after firefighting under wood fire and afternoon measurements immediately after firefighting under gas fire

    Heart rate variability (HRV) measured with the device EndoPAT 2000. The HRV is calculated using the initial 5.5 complete minutes before the cuff is applied. Ratio of low frequency and high frequency bands

  8. Change in Heart Rate Variability ratio LF/HF at rest - morning

    Time frame: Baseline morning measurement, morning measurement in subsequent day after firefighting without fire, morning measurement in subsequent day after firefighting under wood fire and morning measurement in subsequent day after firefighting under gas fire

    Heart rate variability (HRV) measured with the device EndoPAT 2000. The HRV is calculated using the initial 5.5 complete minutes before the cuff is applied. Ratio of low frequency and high frequency bands

  9. Changes in levels of 8-oxodG excretion in first morning urine

    Time frame: Baseline, before firefighting without fire, day after firefighting without fire, before firefighting under wood fire, day after firefighting under wood fire, before firefighting under gas fire, day after firefighting under gas fire

    Oxidized nucleobase 8-oxodG will be measured in urine samples by High-performance liquid chromatography (HPLC) as marker of oxidative stress, together with creatinine, for adjusting for urine concentration. Data will be reported as nanomol 8-oxodG per millimol creatinine.

  10. Changes in levels of DNA strand breaks in peripheral blood mononuclear cells

    Time frame: Baseline, before firefighting without fire, day after firefighting without fire, before firefighting under wood fire, day after firefighting under wood fire, before firefighting under gas fire, day after firefighting under gas fire

    DNA strand breaks will be measured by comet assay, and reported as number of lesions per 10^6 base pairs, transformed from percentage of DNA in tail using the calibration curve from the well-establish relationship between ionizing radiation dose and yield of strand breaks in DNA.

  11. Changes in core temperature

    Time frame: Baseline day, during the day of firefighting without fire, during the day of firefighting under wood fire and during the day of firefighting under gas fire.

    Core body temperature will be assessed by an ingestible pill thermometer with data recorded and reported as time series during the period in transit.

  12. Changes in scrotal temperature

    Time frame: Baseline day, during the day of firefighting without fire, during the day of firefighting under wood fire and during the day of firefighting under gas fire.

    Scrotal temperature will be assessed by skin sensor placed in the scrotum of male participants and reported as scrotal skin temperature time series.

  13. Changes in scrotal thermoregulation

    Time frame: Baseline day, during the day of firefighting without fire, during the day of firefighting under wood fire and during the day of firefighting under gas fire.

    Core body temperature will be assessed by an ingestible pill thermometer and scrotal temperature will be assessed by skin sensor placed in the scrotum of male participants, to assess the thermoregulation of the scrotum during firefighting exercises. Time series of core body temperature and scrotal skin temperature will be analysed for eventual thermoregulation disruption.

  14. Changes in levels of circulating micro RNA

    Time frame: Baseline, before firefighting without fire, day after firefighting without fire, before firefighting under wood fire, day after firefighting under wood fire, before firefighting under gas fire, day after firefighting under gas fire

    Circulating micro RNA candidates will be measured by RNA extraction from serum samples, reverse transcribed into complementary DNA (cDNA) and analysed with quantitative polymerase chain reaction (qPCR).

  15. Changes in urinary potency of AhR activation

    Time frame: Baseline, before firefighting without fire, day after firefighting without fire, before firefighting under wood fire, day after firefighting under wood fire, before firefighting under gas fire, day after firefighting under gas fire

    The aryl hydrocarbon receptor (AhR) activation will be assessed in vitro using urine samples on the PAH CALUX (Chemical Activated LUciferase gene eXpression bioassay) reporter assay. The smoke and soot exposures are complex mixtures of compounds with potential toxic effect. Routine measurements of PAHs are usually quantified for a target list of 16 common soot elements and even less chemical species for urinary metabolites, but many other compounds are present in both soot and metabolites mixtures. The toxicity of PAHs is primarily caused through the binding to AhR, and induction of AhR related genes and subsequent toxic pathways. The outcome will be measured in the form of benzo[a]pyrene equivalence.

  16. Changes in potency of AhR activation from skin deposits

    Time frame: Baseline, before firefighting without fire, immediately after firefighting without fire, before firefighting under wood fire, immediately after firefighting under wood fire, before firefighting under gas fire, immediately after firefighting under gas

    The aryl hydrocarbon receptor (AhR) activation will be assessed in vitro using wipe samples on the PAH CALUX (Chemical Activated LUciferase gene eXpression bioassay) reporter assay. The smoke and soot exposures are complex mixtures of compounds with potential toxic effect. Routine measurements of PAHs are usually quantified for a target list of 16 common soot elements, but many other compounds are present in soot mixtures. The toxicity of PAHs is primarily caused through the binding to AhR, and induction of AhR related genes and subsequent toxic pathways. The outcome will be measured in the form of benzo[a]pyrene equivalence.

Secondary outcomes

  1. Changes in levels of follicle-stimulating hormone in serum

    Time frame: Baseline, before firefighting without fire, day after firefighting without fire, before firefighting under wood fire, day after firefighting under wood fire, before firefighting under gas fire, day after firefighting under gas fire

    Follicle-stimulating hormone (FSH) will be measured in serum samples

  2. Changes in levels of serum inhibin B

    Time frame: Baseline, before firefighting without fire, day after firefighting without fire, before firefighting under wood fire, day after firefighting under wood fire, before firefighting under gas fire, day after firefighting under gas fire

    Inhibin B hormone will be measured in serum samples

  3. Changes in urinary levels of PAH metabolites excretion

    Time frame: Baseline, before firefighting without fire, day after firefighting without fire, before firefighting under wood fire, day after firefighting under wood fire, before firefighting under gas fire, day after firefighting under gas fire

    The internal dose of polycyclic aromatic hydrocarbons (PAHs), that would have the contribution from different exposure routes, will be assessed in first morning urine samples and measured for 7 isomer hydroxyl-PAH compounds and 5 nitro-PAH compounds, measured by high-performance liquid chromatography (HPLC)

  4. Changes in levels of PAHs in skin wipes from the neck

    Time frame: Baseline, before firefighting without fire, immediately after firefighting without fire, before firefighting under wood fire, immediately after firefighting under wood fire, before firefighting under gas fire, immediately after firefighting under gas

    Skin wipes will be sampled to determine the PAH composition of deposited soot on the neck area. The wipes will be analysed for the 16 US Environmental Protection Agency priority list of PAH compounds by HPLC.

  5. Changes in FEV1 spirometric measurements

    Time frame: Baseline, immediately after firefighting without fire, immediately after firefighting under wood fire and immediately after firefighting under gas fire

    Lung function will be measured by spirometry using the Spirometer device EasyOne Air. Forced Expiratory Volume at 1 second (FEV1).

  6. Changes in FVC spirometric measurements

    Time frame: Baseline, immediately after firefighting without fire, immediately after firefighting under wood fire and immediately after firefighting under gas fire

    Lung function will be measured by spirometry using the Spirometer device EasyOne Air. Forced Vital capacity (FVC).

  7. Changes in PEF spirometric measurements

    Time frame: Baseline, immediately after firefighting without fire, immediately after firefighting under wood fire and immediately after firefighting under gas fire

    Lung function will be measured by spirometry using the Spirometer device EasyOne Air. Peak Expiratory Flow (PEF).

  8. Changes in FEV1/FVC ratio from spirometric measurements

    Time frame: Baseline, immediately after firefighting without fire, immediately after firefighting under wood fire and immediately after firefighting under gas fire

    Lung function will be measured by spirometry using the Spirometer device EasyOne Air. Forced Expiratory Volume at 1 second (FEV1) and Forced Vital Capacity (FVC) ratio is calculated from device output.

  9. Changes in blood troponin levels

    Time frame: Baseline, before firefighting without fire, day after firefighting without fire, before firefighting under wood fire, day after firefighting under wood fire, before firefighting under gas fire, day after firefighting under gas fire

    Cardiac troponin levels using ELISA immunoassays will be assessed in serum samples.

  10. Changes in work load measured by muscle activity

    Time frame: Baseline day, firefighting without fire day, firefighting under wood fire day and firefighting under gas fire day

    Muscle activity will be assessed to control for body workload through electromyography (EMG) using the portable device Nexus10. Bipolar surface EMG electrodes are applied to the skin over the muscles in 3 relevant body regions (shoulder, leg and back). The signals are collected with a data logger and reported as work load during a working day.

Sponsors and collaborators

Lead sponsor

National Research Centre for the Working Environment, Denmark

Other Gov

Collaborators

  • Rigshospitalet, Denmark
  • University Hospital Bispebjerg and Frederiksberg
  • University of Copenhagen

Registry information

Official study title

Effect on Markers of Cardiovascular, Reproductive and Cancer Risk From Firefighting Activities - a Study Under Different Training Methods

Acronym: BIOBRAND3

Important dates

Study start
2023
Primary completion
2024
Study completion
2024
First posted
Mar 3, 2023
Registry last updated
Aug 6, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Related clinical trials

Published trials that share one or more normalized conditions with this study.