In case you haven’t heard, a massive wildfire is currently raging across the drought-parched landscape of Butte County in Northern California.
Despite the misleadingly innocent name of the Camp Fire, the blaze has ravaged 57,500 hectares (142,000 acres) in the 11 days since it ignited outside the small rural town of Paradise, near Chico. Having claimed the lives of at least 77 people (almost 1,000 more are currently reported as missing) and destroyed more than 12,000 structures, the Camp Fire is now the deadliest and most destructive wildfire in state history.
Adding to the fire’s devastating human impact, winds have been blowing the toxic smoke west, directly into the highly populated Sacramento region and Bay Area. At the time of writing, the air quality index in San Francisco and the East Bay ranged between about 200 to 320 – hazardous levels considered to represent a population-wide health emergency. The inland East Bay community of Tracy was measured at 404, second only to areas immediately near Paradise.
Based on National Weather Service guidelines, people living in these communities have been encouraged to stay inside, and many schools and businesses were closed on Friday, when smoke pollution peaked.
The air quality index (AQI) measurement being used by monitoring platforms such as the Environmental Protection Agency (EPA)-run AirNow and the privately operated PurpleAir is based on the concentration of a category of particulate matter called PM2.5. Though smoke may appear gas-like, it is actually composed of aerosolized solid and liquid particles that are the byproducts of the combustion. Depending on what is being burned, the resulting particulate matter will vary in toxicity (i.e. a tire fire is more dangerous than a wood bonfire), however, all smoke is dangerous due to the high proportion of small particles that easily absorb through your lung tissue into your bloodstream and enter individual cells.
As the name hints, the PM2.5 category includes all liquid droplets and solid particles that measure 2.5 micrometers in diameter (about one-thirtieth the width of a human hair) or smaller.
“These microscopic particles can get into your eyes and respiratory system, where they can cause health problems such as burning eyes, runny nose, and illnesses such as bronchitis,” the EPA writes. “Fine particles also can aggravate chronic heart and lung diseases – and even are linked to premature deaths in people with these conditions.”