What's different, and worse, about the smoke from the L.A. fires

Los Angeles is already infamous for poor air quality. But the fires scorching the area now are sending up plumes of black smoke that pose threats to human health beyond that of standard wildfires.

Wildfire smoke can linger for weeks and travel across a continent.

But what sets the L.A. fires apart, researchers say, is the toxic mix of substances in the smoke from the burning buildings, vehicles, electronics, plastics and other components of the urban environment, in addition to the trees and other vegetation that typically combust in the wild. Here's what is known about the health risks of such smoke in the short and long term:

In the short term, wildfire smoke, like all smoke, inflames the lungs, says Dr. Chris Carlsten, a professor of medicine and director of the air pollution exposure lab at the University of British Columbia.

But wildfire smoke has its own effects on the blood, which are thought to increase risk beyond the lungs when the blood circulates to the heart. 

Wildfire smoke contains fine particulate matter that can travel deep into the lungs when inhaled. When the lungs get inflamed, scientists suspect they send inflammatory cells into the bloodstream that impact other organs, including the brain.

Smoke can also irritate the eyes and throat leading to itching, coughing and sneezing, Carlsten says.

Acute symptoms can also include chest tightness and wheezing, rapid or irregular heartbeat and excessive fatigue. These symptoms typically ease once the smoke clears, according to the University of California, Davis.

Urban fires combined with wildfire smoke, like what's happening in L.A., don't happen often, and scientists are just starting to study the effects.

Dr. John Balmes, a professor emeritus at the University of California, San Francisco, says such urban wildfires release a cocktail of chemicals from paint, metals, plastic and other synthetic materials beyond what comes from burning vegetation.

Smoke from standard wildfires is "bad enough," said Barnes. "When synthetic materials burn, they give off even more toxic material agents."

For example, Balmes says such fires release benzene, a known cancer-causing agent, which researchers have traced to plastic pipes in a previous urban wildfire in California in 2018. 

The health effects of wildfire smoke exposure over multiple seasons is also a new topic for scientists.

When people with asthma and chronic obstructive pulmonary disease (COPD) breathe in wildfire smoke, they're at higher risk of exacerbations of their condition, which can result in an asthma attack, for instance. Those with lung disease are encouraged to have their medications up to date when wildfire smoke is in the air, says Colleen Reid, an associate professor of geography at University of Colorado Boulder who studies the health impacts of exposure to air pollution from wildfires.