Cross-Seasonal Changes in the Levels of Inflammatory Biomarkers Among Wildland Firefighters

Details

• Personal Author:
  Wu, C. ; Clark, K. ; Adetona, Olorunfemi ; DuBose, Kathleen N. ; Butler, C. ; Croston, Tara L. ; Lemons, Angela R. ; Blackwood, Catherine ; Barnes, Meghan ; Green, Brett J. ; Ramirez-Cardenas, Alejandra ; Odei, James ; West, M. ; Hale, Christa R.
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• Description:
  Background and Purpose: Wildfire activity is increasing in frequency and severity across the United States. Wildland firefighters are the first line of defense against this disaster situation. During firefighting, wildland firefighters are directly exposed to elevated levels of smoke. Exposure to air pollutants from wildland fire smoke, such as respirable particulate matter, can trigger a cascade of inflammatory responses in the lungs, subsequently resulting in systemic inflammation. Increased levels of systemic inflammatory biomarkers after single firefighting shifts and fire seasons have been observed among wildland firefighters. However, studies have rarely assessed how inflammation biomarkers change across and in between fire seasons. This study aims to investigate systemic inflammation status of wildland firefighters across two consecutive fire seasons (2018 and 2019). This research study is part of the Wildland Firefighter Exposure and Health Effects (WFFEHE) Study conducted by the Centers for Disease Control and Prevention (CDC) National Institute for Occupational Safety and Health (NIOSH). Methods: Venous blood was collected among 145 wildland firefighters (aged 28.7 +/- 5.8 years, 92% male) at the beginning and end of the wildfire seasons in 2018 and 2019. A total of nine inflammatory biomarkers, including tumor necrosis factor (TNF-a), interleukin-6 (IL-6), interleukin-8 (IL-8), matrix metalloproteinase-9 (MMP9), C-C motif chemokine ligand 2 (CCL2), angiopoietin- 2 (Ang2), receptor for advanced glycation end products (RAGE), surfactant protein D (SP-D), and uteroglobin (UG), were analyzed and quantified using multiplex ELISA. The values above the limit of detection (LOD) were handled by using the upper detection limit, while the values below the LOD were substituted by the square root of LOD. Most samples (approx. 97%) had TNF-a and IL-6 serum concentrations below the LOD (6.6 and 3.7 pg/ml) and therefore these two cytokines were excluded from the following statistical analyses. Linear mixed model (LMM) using SAS MIXED with autoregressive 1 (AR1) variance-covariance matrix was used to determine the changes in the levels of biomarkers among the firefighters. Paired samples from the firefighters were analyzed as follows: 1) combined 2018 and 2019 post- minus pre-season changes; 2) off-season changes (pre-season 2019 minus post-season 2018); and 3) changes across follow-up period (post-season 2019 minus pre-season 2018). Age, smoking status, and the number of firefighting incidents during wildfire season were included as covariates in the model. A p-value < 0.05 was considered statistically significant. Results: There were 20% and 17% of IL-8 samples below the LOD (3.1 pg/ml) in pre- and post-season, respectively. For MMP9, 12% and 11% of serum samples were above the LOD (29.25 µg/ml) in pre- and post-season, respectively. Similarly, 19% and 36% of UG concentrations were higher than its LOD (10.63 µg/ ml) in pre- and post-season, respectively. Testing values of all other biomarkers were within the detection range. CCL2, RAGE, SP-D, and UG significantly increased across the fire season when the 2018 and 2019 measurements were combined (0.06 +/- 0.01 µg/ml, p < 0.01; 0.25 +/- 0.07 µg/ml, p < 0.01; 1.17 +/- 0.25 µg/ml, p < 0.01; 0.74 +/- 0.13 µg/ml, p < 0.01, respectively). Overall Ang2 significantly decreased after the fire season (.0.30 +/- 0.06 µg/ml, p < 0.01). MMP-9, CCL2, RAGE, SP-D, and UG significantly decreased during the off-season (.5.28 +/- 1.10 µg/ml, p < 0.01; .0.07 +/- 0.02 µg/ml, p < 0.01; .0.29 +/- 0.10 µg/ml, p = 0.01; .2.01 +/- 0.48 µg/ml, p < 0.01; .0.67 +/- 0.15 µg/ml, p < 0.01, respectively). CCL2 and UG significantly increased from 2018 pre-season to 2019 post-season (0.06 +/- 0.02 µg/ml, p = 0.01; 0.78 +/- 0.30 µg/ml, p = 0.01, respectively), but MMP-9 and Ang2 significantly decreased during the same period (.5.08 +/- 1.39 µg/ml, p < 0.01; .0.42 +/- 0.12 µg/ml, p < 0.01, respectively). Conclusions: The results suggest wildland firefighting generally alters the levels of biomarkers across the wildfire season, reflecting systemic inflammatory response. As indicated by the reduction in the concentrations of most of biomarkers (MMP-9, CCL2, RAGE, SP-D, and UG) during the off-season period, a break from wildland firefighting seemed to alleviate the inflammatory response. Description provided by NIOSH
• Subjects:
  • Firefighters
  • Inflammation
  • Occupational Health
  • Safety
  • Wildfires
• Keywords:
  • Fire fighters; Wildfires; Biomarkers; Immune reaction; Seasonal factors
• Source:
  Toxicologist 2025 Mar; 204(S1):604
• ISSN:
  1096-6080
• Document Type:
  Text
• Genre:
  Abstract or Summary
• Place as Subject:
  Chicago Region OSHA ; Colorado ; Denver Region OSHA ; Montana ; Ohio ; Philadelphia Region OSHA ; West Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  RHD - Respiratory Health Division ; WSD - Western States Division ; HELD - Health Effects Laboratory Division
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  2 pdf pages
• Volume:
  204
• NIOSHTIC Number:
  nn:20071590
• Federal Fiscal Year:
  2025
• Peer Reviewed:
  False
• Download URL:
  https://stacks.cdc.gov/view/cdc/259365/cdc_259365_DS1.pdf
• File Type:
  [PDF - 240.60 KB]
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:b7489a812dd4463a902e49902ccf2189463c28a8a8ebf3b8f2a85c11c23ed69b399d0ddab142e0b1ccc7857693c6f2ca7bc9b7c269b7c100f6e01c2cd3577217