November 29, 2007
Several recent letters to the editor have incorrectly stated that residential wood burning is a relatively minor contributor to air pollution in the Bay Area compared with other sources, such as motor vehicles. It would be helpful if these letter writers checked the facts on web sites and available from governmental agencies based on measurements of fine particulates in the air caused by fireplaces, wood burning, and other sources. Wood burning is the largest single source of fine particulate air pollution on bad-air days in the Bay Area, accounting for 33% of the total. Based on scientific studies of the chemical makeup of the air, the Bay Area Air Quality Managemet District estimates, by comparison, that 23% of the fine particles come from on-road vehicles. It is not surprising that residential wood burning is such a large contributor to particulate air pollution in the Bay Area, since we are surrounded by the coastal mountains and most of the burning occurs on cold wintertime evenings when the air is very still, causing the particles to hug the ground in our neighborhoods for long time periods where they can cause the most harm to health.
I am a scientist and a Consulting Professor of Civil and Environmentall Engineering at Stanford who has studied residential wood smoke in the Bay Area for many years. Most of the facts that I cite in my letter were published in the pie chart alongside the news article by Johnathan Curiel "Proposal to Ban Fires on Smoggy Winter Days", Chronicle, p. B-1, Tuesday, November 6, 2007, but most of these letter writers appear to be unfamiliar with these facts. I am concerned that erroneous information published in these letters may contribute to a misunderstanding by the public of the seriousness of wood burning pollution in the Bay Area, and I am trying to correct the record by the short letter I am submitting above, without being critical of anyone.