A reader made an important point about my Sunday story on wood-burning restrictions during winter. Soot from wood fires in winter is really only 10% of the particle pollution in the San Joaquin Valley on the worst days, not 30%, as the story says.
The reader is right to say there is a much bigger source of particle pollution, known as PM-2.5. But I was not writing about all sources of PM-2.5 — just the ones that are the most dangerous in your city neighborhoods. I deliberately wrote it that way and for good reason.
I’ll just repeat it. The biggest PM-2.5 danger in winter around your city neighborhood is soot coming from a wood fire, not simply the largest source. I’ll get to the 30% figure in a minute.
Why am I talking about cities — Bakersfield, Fresno, Clovis, Visalia, Hanford, Modesto, Stockton and the other cities? That’s where the majority of the San Joaquin Valley’s breathing public live.
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Here’s how I wrote the description of the pollution: “soot from November to February when 30% of dangerous particle pollution comes from wood fires in city neighborhoods.”
I was paraphrasing the San Joaquin Valley Air Pollution Control District, which has long said that up to a 30% of the particle pollution in city neighborhoods during winter comes from wood burning.
As the reader suggests, wood smoke is not nearly the largest source, ammonium nitrate. It forms when plumes of ammonia from dairies combine with oxides of nitrogen from vehicles.
But scientists have established the toxicity of the organic carbon particles coming from wood burning and diesel exhaust. They are the biggest health concerns with consequences including lung and heart ailments as well as premature death. Ammonium nitrate does not represent the same kind of threat, scientist say.