LA fire smoke triggered surge in airborne toxins: How long did they stay

When wildland-urban interface fires sweep across Southern California, the smoke carries far more than standard vegetation ash.

Lead Spikes 250 Times Normal Baseline

Air quality downwind saw sharp, immediate increases in harmful pollutants while the fire was actively burning, according to UCLA researchers. Airborne lead levels surged up to 250 times above normal baseline levels. Alongside lead, the smoke carried extremely elevated levels of arsenic, chlorine, bromine, and copper.

Suzanne Paulson, professor of atmospheric and oceanic sciences and director of UCLA’s Center for Clean Air, noted the immediate risks faced by surrounding communities as these complex urban-wildland fires become more frequent in the Los Angeles region.

Tracking Smoke Pathways from UCLA to Huntington Park

To understand how smoke and dust traveled through local neighborhoods, researchers combined air quality data from two monitoring stations located downwind of the fire. One monitor sat on the UCLA campus, while the other was stationed at the South Coast Air Quality Management District’s Huntington Park Station, situated roughly 17 miles south-southwest of the fire’s start. By pairing this monitoring data with satellite fire tracking and wind models, the team successfully separated fire smoke data from everyday city emissions.

However, isolating the precise source of specific contaminants proved challenging. Catherine Banach, a UCLA Ph.D. student researcher and co-author of the study, explained that elements like lead, arsenic, zinc, bromine, and chlorine typically appear in higher concentrations in smoke from urban fires. Yet, researchers observed that these elements persisted even after the flames moved away from urban areas and shifted into wildlands.

Elements like lead, arsenic, zinc, bromine and chlorine are expected to be higher in smoke from urban fires, but we found that they persisted even when the fires shifted away from the urban areas and into the wildlands.

Catherine Banach, UCLA Ph.D. student researcher and co-author

The study also revealed unexpected findings regarding potassium, which is traditionally used as a marker for burning vegetation. Instead of correlating with increased smoke levels, potassium tracked with dust particles kicked up by winds. Researchers noted this complexity emphasizes the need for a deeper understanding of local soils before using standard indicators to assume emission sources.

Air Quality Returns to Normal Within Six Days

Despite the severe initial surge in contaminants, the heavy metals and smoke did not linger in the atmosphere long-term. UCLA researchers found no evidence that toxic smoke or heavy metals stayed in the air after the fires were put out. Pollution levels returned to normal background conditions within roughly six days after the flames were extinguished, and air quality remained stable for months afterward.