Eaton Fire exposed Los Angeles residents to elevated lead, study finds

Smoke from the 2025 Eaton Fire exposed millions of Los Angeles residents to elevated lead, with concentrations reported at roughly 80 times normal atmospheric levels, according to a Caltech study.

The research described the fire’s urban smoke plume as having more lead than typical wildfire smoke; the New York Post reported the comparison as more than 50 times the lead concentration. ScienceAlert reported that by January 9, smoke had blanketed around 7 million residents.

The study team’s reported mapping found that approximately 7 million residents experienced lead concentrations above 50 nanograms per cubic meter on January 9. Those figures describe the population and concentrations reported in the study, not a count of people with measured individual exposure. The outlets emphasize different aspects of the findings.

The New York Post highlights the plume’s comparison with typical wildfire smoke, reporting that it contained seven times the halogens and three times the arsenic as well as more than 50 times the lead.

ScienceAlert focuses on the extent of exposure across Los Angeles and gives a local baseline: daily lead at Pico Rivera averages 0.6 nanograms per cubic meter under typical conditions. The two accounts identify the fire’s start as January 7, 2025.

ScienceAlert says Santa Ana winds pushed flames from Eaton Canyon into Altadena; the New York Post says the Eaton Fire started at the same time as the Palisades Fire. The reported findings concern smoke from the Eaton Fire and the scale of lead exposure, rather than a comparison of health outcomes among residents.

The study’s reported measurements place the smoke plume’s lead levels far above the typical atmospheric level described in the coverage. ScienceAlert reports that the January 9 estimate came from overlaying daily lead maps with census data.

That approach supports an estimate of how many residents lived in areas with reported concentrations above the stated threshold; it is not the same as measuring each resident’s personal exposure. The New York Post also reports that the study found elevated levels of other metals alongside lead.

Its excerpt characterizes the smoke mixture as linked to burning vehicles, electronics and building materials. The reporting identifies that as an explanation associated with the research, while the central quantified finding is the reported lead concentration and the estimated population exposed.

The findings focus attention on the air-quality consequences of an urban fire plume extending across a densely populated area. In particular, the reported estimate of millions exposed above 50 nanograms per cubic meter and the comparison with Pico Rivera’s typical daily average show the scale of the difference described by the study.

The coverage does not provide a separate estimate of illness or other health outcomes attributable to the exposure.