12-07-2025
Poor air affects you even if you don't smell wildfire smoke: Air pollution explained
Smoke from the Green Fire and other wildfires burning in and near Shasta County are polluting the air over the North State.
The Shasta County Air Quality Management District and Shasta County Health and Human Services Agency advised people — especially those with health issues — to stay indoors when air is smoky.
However, just because you don't smell smoke doesn't mean the air is clean, according to the U.S. Environmental Protection Agency.
Here's where Shasta County's air is smokiest and how air can be polluted even without that smoke smell.
While smoke can fill the air at any time, according to forecasters, Redding, Shasta Lake and Anderson will get more smoke as it settles into the valley at night and early in the mornings, public health said.
Areas most affected by Green Fire smoke are Bella Vista, Palo Cedro, Shingletown, Round Mountain, Big Bend and Burney, according to the county.
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While wildfire smoke is unhealthy, people and animals are also at health risk from what they can't smell.
Fires send a mixture of smoke and tiny particles called PM 2.5 — particulate matter — into the air. When you smell smoke, you're actually smelling just the gases, not the particles, said University of California, San Francisco pulmonologist Dr. John Balmes, an expert on the respiratory and cardiovascular effects of air pollution. Gases and PM 2.5 are side-by-side at the site of a fire, but the particles waft higher into the air at a short distance from the flames.
That's why you can have bad air — air high in PM 2.5 — without smelling smoke or gases.
PM 2.5 contains "microscopic solids or liquid droplets that are so small, they can be inhaled and cause serious health problems,' according to the EPA's PM 2.5 pollution website.
Air quality scientists measure the amount of PM 2.5 in the air. When air quality is ranked "unhealthy," it means there's enough PM 2.5 in the air to cause health problems, according to AirNow.
The particulates "have the ability to get deep into the lung,' Balmes said. 'They cause inflammation, which is the response of the body to injury of any type. When you breathe in these fine particles to your lungs it causes injury. Once there's inflammation in the lungs, it can exacerbate lung (and) heart conditions.'
When air is unhealthy, everyone should reduce the amount of time they spend outdoors if they can, the EPA warns. However, some people are especially vulnerable to the effects of bad air.
When air quality is ranked "unhealthy for vulnerable groups" it means PM 2.5 are at levels that can cause problems for people with medical conditions, especially respiratory issues like asthma and heart or lung disease. Certain age groups — older adults, children and teens — are also vulnerable to problems from bad air, according to the EPA.
When PM 2.5 levels are so high they can hurt anyone, air is ranked "unhealthy", "very unhealthy" or "hazardous" by the EPA. In these cases, everyone should limit prolonged exposure.
The EPA's website at can tell you how much PM 2.5 is in your air. It also offers health and lifestyle advice based on that result.
Here's what public health branches recommend people do when air is polluted.
Limit outdoor activities.
Remain indoors with the windows and doors closed.
Turn on an air conditioner with a re-circulation setting, like in a vehicle.
If you do go out, choose less strenuous outdoor activities. For example, go for a walk instead of a run.
To learn more about particulate matter go to the California Air Resources Board website at
Jessica Skropanic is a features reporter for the Record Searchlight/USA Today Network. She covers science, arts, social issues and news stories. Follow her on Twitter @RS_JSkropanic and on Facebook. Join Jessica in the Get Out! Nor Cal recreation Facebook group. To support and sustain this work, please subscribe today. Thank you.
This article originally appeared on Redding Record Searchlight: Don't let poor air quality, wildfire smoke affect you, Californians
