Chemical Complexity and Enrichment in Wildland-Urban Interface Fire Emissions: A Case Study of Particulate Matter, Gas-Phase Pollutants, and Ash from the 2025 Los Angeles Fires

Details

• Journal Article:
  Journal of Hazardous Materials
• Personal Author:
  Cedeño-Laurent, Jose G. ; Calderón, Leonardo ; Tsiodra, Irini ; Pradeep, Sanjay ; Davey, Hope ; Rahmati, Roxana ; Bazina, Lila ; Fu, Xianqiang ; Batbaatar, Namuun ; Tsai, Candace S. J. ; Mihalopoulos, Nikolaos ; Sarkar, Dibyendu ; Jia, Chunrong ; Baalousha, Mohammed ; Demokritou, Philip
  More +
• Description:
  The Los Angeles (LA) wildland-urban interface (WUI) fires of January 2025, are among the most destructive natural disasters in U.S. history, generating complex emission profiles that remain insufficiently characterized. An intensive field sampling campaign was conducted during the active burn period to collect and characterize the complex physicochemical properties of size-segregated particulate matter (WUIF-PM), vapor-phase compounds (WUIF-VOC), and ash (WUIF ash). While regulatory air quality indices remained within moderate categories during the sampling period, chemical analyses revealed substantial enrichment of hazardous species relative to urban background and biomass-only wildfire conditions. Oxygenated and highly toxic polycyclic aromatic hydrocarbons (OPAHs) were found in ultrafine WUIF-PM0.1, (size < 100 nm) and the fractional concentration (µg/g) of US EPA 16 priority polycyclic aromatic hydrocarbons (PAHs) in WUIF-PM2.5 exceeded recent levels for LA background, and biomass-only wildfires by an order of magnitude due to the excessive burn of human-made structures. Non-crustal metals were predominantly concentrated in WUIF-PM0.1 and consistently enriched relative to both LA background (up to approx. 30x) and biomass-only wildfire aerosols (10-1000x). Benzene, toluene, ethylbenzene, and xylene (BTEX) concentrations in WUIF-VOC air samples were 4.8-13-fold higher than background levels. More alarmingly, WUIF ash samples contained PAHs, metals, and per- and polyfluoroalkyl substances (PFAS) consistent with mixed combustion of structural materials and vegetation raising concerns for post-fire environmental health risks. These findings indicate that PM2.5 mass and criteria air pollutants alone may underestimate the toxicological burden of WUI smoke, and expanded physicochemical monitoring and characterization is needed to advance exposure assessment and health risk evaluation during complex WUI fire events. Description provided by NIOSH
• Subjects:
  • Air Pollution
  • Fires
  • Occupational Health
  • Particulate Matter
  • Safety
  • Wildfires
• Keywords:
  • Wildland fire smoke; Particulates; Ultrafine particles; Wildfires; Natural disasters; Hazardous materials; Polycyclic aromatic hydrocarbons; Air pollution sampling; Per- and polyfluoroalkyl substances; PFAS;
  • Author Keywords: WUI fires; Wildfires; Ultrafine particulate matter; PAHs; LA Fires
• Source:
  J Hazard Mater 2026 Jul; 512:142357
• ISSN:
  0304-3894
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  Atlanta Region OSHA ; Birmingham Region OSHA ; California ; New Jersey ; New York City Region OSHA ; San Francisco Region OSHA ; South Carolina ; Tennessee
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  12 pdf pages
• Volume:
  512
• NIOSHTIC Number:
  nn:20071689
• Contact Point Address:
  José Guillermo Cedeño-Laurent, Department of Environmental and Occupational Health and Justice, Rutgers School of Public Health, Piscataway, NJ 08854, USA
• Email:
  memo.cedeno@rutgers.edu
• Federal Fiscal Year:
  2026
• Performing Organization:
  University of California Los Angeles
• Peer Reviewed:
  True
• Start Date:
  20050701
• End Date:
  20270630
• Download URL:
  https://stacks.cdc.gov/view/cdc/259460/cdc_259460_DS1.pdf
• File Type:
  [PDF - 5.74 MB]
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:f4fc3ea68b31c06650277b7f9fa256a1a495a9ac24d2e728ad5bd25603e5d3e2f6d1fb9762622fa883dc3e6a5cc809d54041c8ed4d2b0b46c50fbd5ad4928efc