Researchers share detailed air quality data as questions linger over toxic chemicals

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What they observed: In the days after the fire started, a monitoring site in Pico Rivera observed spikes in three chemicals: lead, bromine, and chlorine. The spike in lead was especially notable since it’s usually detected only in trace amounts, according to researcher and Caltech PhD student Haroula Baliaka, who monitors that site's data.

Where the levels are now: “ You can tell that the levels now have kind of gone back to normal, and especially with lead,” Baliaka said. “There's a clear spike from the [Eaton Fire] plume, and then it goes back to normal.”

Caveats in the data: Co-lead researcher Roya Bahreini said the team hasn’t traced exactly what caused the spikes — and researchers also say the real-time measurements are preliminary and haven’t been fully vetted. The sensors detect particles that are smaller than 2.5 microns, so many larger ash particles aren’t picked up.

Possible explanations: Although researchers haven’t traced the chemicals’ origin, they have some hypotheses. Spikes in bromine levels may be related to fire suppressant compounds in mattresses and other household items, while lead may be related to paint and infrastructure in older houses that burned. Chlorine may have originated from PVC piping as well as pool supplies. Car batteries and electronics that burned may also be contributors to chemical levels.

The data set: You can see the data set for the three sites in Southern California here. The data are collected as part of the Atmospheric Science and Measurement Network (ASCENT for short), which monitors air quality at sites across the country.

For more information: South Coast Air Quality Management District has resources and information, including pollutant maps, here. LAist also has guides on how to keep yourself safe from potentially toxic ash and a breakdown of air quality ratings.