TL;DR LA Post Fire: Hexavalent Chromium (Chrome-6) Results Q&A

TL;DR
LA Post Fire: Hexavalent Chromium (Chrome-6) Results Q&A

Host: iO Tillet-Wright, wildfire survivor and activist
https://www.iolovesyou.com/
https://postfirela.org

Guests (LA Fire Health Study Scientists):

  • Dr. Michael Kleeman – UC Davis

  • Dr. Joe Allen – Harvard School of Public Health

  • Dr. Mike Jarrett – UCLA

  • Dr. Yifeng Zhu – UCLA

  • Dr. Kerry Nadeau – Stanford / LA Fire Health Study

Supporting Organizations:
Resilient Palisades
Eaton Fire Residents United (EFRU)
CAP LA
USC CLEAN
LA Fire Health Study – https://lafirehealth.org

 

What Was Studied

  • Air monitoring conducted March–May during peak debris removal

  • Focus initially on lead and arsenic, expanded to other metals

  • Scientists detected elevated hexavalent chromium (Chrome-6) in air samples:

    • Within burn zones

    • Up to 1–6 miles from burn scars (Altadena & Palisades)

 

What Is Hexavalent Chromium (Chrome-6)?

  • A toxic form of chromium

  • Classified by the EPA and WHO as a human carcinogen

  • Can cause:

    • Respiratory irritation

    • Long-term lung cancer risk with chronic exposure

  • Wildfires can transform chromium-3 (common in metal products) into chromium-6 under extreme heat

  

Key Findings 

  • Average measured level: ~13.7 ng/m³

  • Levels were:

    • Below EPA limits for outdoor workers

    • Above EPA screening thresholds for indoor air

  • Measured levels were:

    • 225–345x higher than typical LA background air levels

    • ~25x higher than areas near chrome-plating facilities

  • Most concerning factor:

    • Chrome-6 was concentrated in ultrafine nanoparticles (<56 nm)

 

Why Particle Size Matters

  • Ultrafine particles:

    • Penetrate deep into lungs

    • Can enter bloodstream

    • May cross cellular barriers

  • Existing EPA standards are based on larger particles, not nanoparticles

  • This creates uncertainty → more research is required

 

Exposure Time & Risk Context

  • Cancer risk is calculated over 30-year average exposure

  • Short-term elevated exposure (3–4 months):

    • Unlikely to meaningfully increase cancer risk

  • Primary concern is if levels:

    • Persist long-term

    • Do not return to pre-fire background levels

 

Trend Over Time (Good News)

  • Ratio of Chromium-6 to Chromium-3 declined over time

    • ~90% Chrome-6 initially

    • ~53% by month three

  • This matches expected chemistry and suggests levels may continue dropping

 

Current & Ongoing Testing

  • New air testing underway (next 3–4 weeks)

  • Soil testing currently in progress (UCLA / CAP LA)

  • Biomonitoring study:

    • ~120 participants across both fires

    • Blood testing for chromium exposure

    • Results expected within ~1 month

  • Indoor air testing underway (critical, as people spend ~70% of time indoors)

 

Water Testing

  • Chrome-6 not detected at concerning levels in water

  • Erin Brockovich comparison:

    • That case involved water exposure at much higher levels over many years

    • Not comparable to current LA fire conditions

 

Geographic Impact Estimates

  • Potential affected area: 1–6 mile radius

  • Estimated population within range: 200,000–500,000

  • This represents a worst-case scenario

    • Wind direction and speed significantly affect exposure

 

Mitigation & Safety Guidance

  • HEPA air purifiers ARE effective, including for nanoparticles

    • Common myth: HEPA only filters down to 0.3 microns (false)

    • Smaller particles are also efficiently captured

  • If you’ve been running HEPA filters:

    • You’ve likely already reduced exposure

  • Outdoor activity:

    • Walking outside is not considered dangerous

    • Avoid heavy outdoor exercise or dust-disturbing activities until follow-up results

 

Who Is Most At Risk?

  • Individuals with:

    • Pre-existing respiratory conditions

    • High sensitivity to air pollutants

  • Possible symptoms at high exposure levels:

    • Eye, nose, throat irritation

    • Allergy-like symptoms (non-specific)

 

Why This Was Shared Early

  • Findings are in pre-print (not yet peer-reviewed)

  • Released early because:

    • Potential public health relevance

    • Community deserved calm, factual information first

  • Government agencies were notified within 12 hours

  • Goal: awareness, not panic

 

What Happens Next

  • Continued monitoring

  • Rapid public updates as new data becomes available

  • Coordination with:

    • State and local air quality agencies

    • Public health departments

  • Community updates via:

 

Core Takeaway

  • Elevated Chrome-6 was detected during debris removal

  • Levels appear to be declining

  • Short-term exposure is unlikely to cause acute harm

  • Persistence over time is the key risk factor

  • Ongoing testing will determine next steps