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2h ago

Preprint Detects Chromium-6 Nanoparticles in L.A. Fire Cleanup Zones

Researchers call for expanded monitoring following measurements above outdoor screening levels with averages below worker limits.

An aerial view of surviving structures and cleared lots taken in June in Altadena, where the Eaton Fire burned through several months earlier.
Athira Satheesh, left, and Dawn Bolstad-Johnson collect samples for testing inside a home that survived the Eaton Fire in Altadena.
© eley archive via Shutterstock
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Overview

  • Mobile sampling in March and April near the Eaton and Palisades debris zones measured average hexavalent chromium at 13.7 ng/m3 and silver at 1.6 g/m3, with more than 90% of the silver present as nanoparticles.
  • The chromium-6 was concentrated in particles smaller than 56 nanometers, a size associated with deeper lung penetration and potential movement into the bloodstream.
  • Citywide averages were below NIOSH and EPA worker thresholds yet exceeded ambient-air screening values, and additional real-time readings pointed to hotspot total chromium above 100 ng/m3.
  • The results were released Aug. 28 as a UC Davis–led preprint from the LA Fire HEALTH Study and remain unreviewed, with more sampling planned to track persistence and map hotspots.
  • Health guidance urges HEPA or MERV-13 filtration, KN95/N95 masks, and wet cleaning, while investigators examine unconfirmed sources such as burned electronics and chrome-containing fire suppressant.