Dangers from urban wildfire smoke

As the Palisades, Eaton and Hurst fires continue to sweep Los Angeles, millions of people could be affected by the smoke from these urban wildfires. The dangers of wild wildfire smoke are well documented, but scientists only have a rudimentary understanding of the composition of urban wildfire smoke.

Unlike wild forest fires fueled by vegetation, urban fires burn buildings, vehicles, factories, and a variety of consumer and industrial products made from many different chemicals and materials. In addition, this disaster occurred in a densely populated area, so the smoke immediately became a major threat to the local community.

In 2023, a research team from the US Environmental Protection Agency (EPA) compiled data from 28 separate analyzes of smoke emitted in urban fires, comparing it with the chemical composition of wild forest fire smoke. wild. As a result, both types of fires emit similar amounts of CO2, CO and fine dust. These are all major health hazards.

However, smoke from urban fires also contains many other dangerous substances in high concentrations. For example, polycyclic aromatic hydrocarbons (PAHs) are a group of potentially carcinogenic chemicals with an emission factor three orders of magnitude higher than wild wildfire smoke. Formed naturally in coal, crude oil, and gasoline, PAHs are also found in cigarette smoke and are associated with certain blood and liver disorders.

Some other dangerous chemicals such as dioxins and furans in urban fire smoke are even 5-6 orders of magnitude higher than in vegetation fires. These substances have been shown to disrupt hormone regulation, inhibit fertility, and contribute to cancer.

Research also shows that urban wildfire smoke contains high concentrations of toxic organic compounds benzene, toluene, ethylbenzene, xylenes – collectively known as BTEX. This group of compounds is also present in vehicle exhaust and cigarette smoke, and has been linked to cancer and autoimmune disorders.

Given the diversity of urban materials, it is not surprising that fires like the one in Los Angeles would release a complex combination of toxic chemicals, and the list is certainly not over. For example, phosgene produced when plastic burns can cause lung damage and respiratory failure. Heavy metals such as lead, chromium, cadmium, and arsenic are also released into the air when urban fires occur.

Currently, it is difficult to accurately determine the level of air pollution or risk to human health from the Los Angeles fires. However, forest fire smoke can travel very far and affect people thousands of kilometers away from the fire source. As climate change increases both the frequency and intensity of wildfires, the threat to public health is likely to increase in the coming years.