Sparking Firefighter Safety: ASU wildland firefighter hydration study

The aim of this study is investigating the field-based validity of hydration self-assessment by wildland firefighters (WLFs) using simple biomarkers, such as body weight change, urine frequency, urine color, and thirst, as shown in Figure 1, and determine the effect of education and self-assessment on improving hydration status.

For this purpose, we developed two aims:

Aim #1: To identify the optimal combination of ‘simple self-assessed biomarkers’ and time of day for hydration assessment.

Aim #2: To assess the efficacy of hydration education and the use of a self-assessment worksheet vs. a no-intervention control on improving fluid intake and hydration status in underhydrated WLFs.

This research will result in:


This is important as cardiovascular disease (CVD) is the leading cause of on-duty death (45% of fatalities) in the U.S. WLFs work under arduous conditions and maintaining good hydration status is critical for performing required tasks.

This study will have a dramatic positive effect on the wildland fire service, as it will allow those with a need to improve their hydration by using a combination of simple measurements, and it will provide suggestions for a more standardized approach to hydration self-assessment. For this reason, we will provide feedback to all participants as soon as possible. This will help keep firefighters and management engaged in the project, and it allows participating WLFs to learn from their own results.

From a general perspective, although we do not have exact numbers, improving hydration status in WLFs with underlying risk factors for CVD may be very impactful for their health. From the start of 2012 to the end of 2021, a total of 959 fatalities were reported, of which roughly half (48%, #459) were classified as caused by stress/overexertion – suggesting on average ~50 fatalities per year. The nature of most of these injuries was cardiovascular: heart attack (#411) and cerebrovascular (#32). These fatalities are a basic measure of firefighter population health, suggesting that ensuring a sufficient hydration status can have a substantial impact on firefighting health. Additionally, in 2021 over 60,000 firefighter non-fatal injuries were reported, and roughly 50% of those injuries (45% strain, sprain, and muscular pain, and 5% thermal stress) could be related to impaired hydration. As hydration plays an important role in WLF safety, health, and wellness (including an improved state of mood and better executive decision-making), this project will directly and positively impact the mission of the current grant NOFO, targeting WLF safety. The project materials (i.e., education materials, instruction manual and presentation, and the final version of the hydration self-assessment worksheet) will be freely available and will aid in WLF training and education.


Due to the nature of this project, first focusing on the validity of hydration self-assessment, and second on improving hydration of WLFs with a high urine concentration, the research team will provide outcome-based: 1) knowledge on hydration self-assessment, as well as its impact on hydration status, 2) educational materials (i.e., a number of short instructional videos for WLFs that will aid in the instruction of the worksheet, two fact sheets representing the importance of good hydration, and reporting a summary of the study outcomes), and 3) a self-assessment worksheet to track hydration (Appendix 3) throughout and beyond the regular fire season for those that would benefit from optimizing their hydration status. To implement our results, we will develop clear educational materials and instructions for self-assessment that will be shared with the Tonto National Forest fire crews, as well as with USFS, FEMA, and the other partner organizations that provided their support who can then share this information with their members. We will work locally with the Wildland Fire Education Officer (Jonathan McLaughlin) to implement our knowledge and materials with crew leadership and crew member training throughout Arizona.