This article is part of Shasta Scout’s wildfire-related coverage. As an emerging news media organization, we’re focusing on stories connected to, and surrounding, our local wildfire emergencies in an effort to best utilize our investigative reporting skills to support our community.


Thick smoke from multiple large wildfires near Shasta County has choked Shasta County air over the last several weeks. Air Quality Index (AQI) readings have hovered between unhealthy and hazardous. As wildfires, particularly in the western U.S., increase in size and severity, research is beginning to show the significant impact of wildfire smoke to both short and long-term health. 

While wildfire smoke exposure can irritate eyes and airways, worsen asthma and contribute to cardiac events and strokes, it’s also linked to a decrease in the body’s ability to fight off bacteria and viruses in the lungs. That’s relevant to new research published in August, that indicates short-term wildfire smoke exposure increases the risk of both contracting and dying from COVID-19. Other new research recently found that wildfire may increase toxic metals in the air. After the Camp Fire in 2019, toxic levels of lead and zinc were found in the air more than a hundred miles away.

And since California is likely to see a decade of explosive fires before fuel loads are used up and fires decrease in frequency and severity, this public health concern isn’t likely to go away.

John Waldrop, Shasta County’s Air Quality District Manager, says wildfire smoke impacts in Shasta County are serious and concerning. Here’s more of what you need to know. 

Is the smell and sight of smoke a reliable indicator of how toxic the air is? 

To some extent, yes, Waldrop says; “the saying is that if you see smoke, and smell smoke, then you’re breathing smoke.  And the more smoke you see and the stronger it smells, the more smoke you’re breathing.”  

But Waldrop was quick to add it’s easy to become desensitized to the sight and smell of smoke during wildfire events. People may think a decrease in visible smoke means the air is clean when really pollutants have just decreased, not disappeared.  

The bottom line? The sight and smell of smoke is not a reliable indicator of dangerous air quality. Check the AQI instead. 

What’s in wildfire smoke that makes it so dangerous to our health? 

Wildfire smoke is a mixture of many different particle sizes.

Waldrop explains that the products of combustion behave similarly to a handful of dirt thrown into the air, which will separate into big heavy chunks, smaller chunks, and fine dust that blows away.  

Wildfire smoke contains particles small enough to integrate into the air we breathe.  Those particles, which are measured in microns, can be dangerous to health. Waldrop says that’s because particles smaller than 2.5 microns or PM 2.5, can penetrate into the deepest parts of our lungs, into the alveolar sacs, and penetrate the walls where oxygen exchange is happening.  This allows particulate matter to enter our bloodstreams where it can harm vital organs and affect immunity. 

The Centers for Disease Control and Environmental Protection Agency say wildfire smoke exposure risks increase based on how long people are exposed to the smoke and the amount of particles people are exposed to, which is one reason why air quality monitoring is so important. Smoke from burning cars and buildings is particularly hazardous because of the chemicals that can be released when these materials burn.

Who is most affected by wildfire smoke and what health hazards does it create? 

Generally, babies and children, pregnant women, the elderly and those with heart or lung conditions or diabetes are most at risk. The high respiratory rates of young children makes their exposure to wildfire smoke particularly concerning because they are breathing in more particulate matter. 

Risks are also increased by disparities related to racial and economic inequity. Where you live, and work, how much money you have, your transportation options, your ability to travel away from smoke, and your access to health insurance, among other factors, can significantly impact your risks during adverse air quality events. 

How is Air Quality Monitored in Shasta County? 

Prior to the Carr Fire, Waldrop explains, Shasta County’s air monitoring was done through several official air monitoring sites, using very sensitive sensors designed to provide the highly specific data needed to meet state and federal air quality monitoring standards. Those sensors cost $15,000–$20,000 each, Waldrop says, and require significant maintenance and auditing by staff to ensure proper function.

Things changed around the time of the 2018 Carr Fire, when Shasta County deployed several low-cost Purple Air sensors, provided by the California Air Board. 

Purple Air, a Utah startup begun in 2015, sells air sensors to individuals and businesses, then utilizes data from those sensors by crowd-sourcing it to provide air quality mapping. Waldrop, like many air experts, says the benefit of Purple Air sensors is that their low cost and accessibility means broad deployment of sensors. The downside, he says, is that they may be installed improperly or in an unhelpful site, like near a dusty road or by a charcoal grill. 

Without any quality control over how or where the sensors are set up, Waldrop says, Purple Air’s monitoring can give misleading results. Purple Air sensors have also been found by studies to skew to higher-than-appropriate AQI readings when exposed to higher smoke concentration, Waldrop says, which can create false measurements. 

What’s the Best Site or App for Air Quality Monitoring in Shasta County?

Waldrop recommends the EPA site AirNow, which utilizes Purple Air sensors as well as official government sensors and incorporates a correction factor that increases the accuracy of Purple Air sensors. The same correction factors are available on the Purple Air site, Waldrop says, but require toggling between views of sensors, something that often confuses users.

What do the different symbols on the AirNow air quality monitoring map mean? 

The combination of squares, triangles and circles on the AirNow site simply indicate what kind of air sensor is being used at that specific location, Waldrop says. By far the most common symbols, squares, indicate Purple Air sensors, generally deployed by Air Quality Management Districts like the one Waldrop manages, but many of which have been installed by private users, including business owners. The three triangles on the Shasta County AirNow map indicate the three portable official air sensors that the county has deployed in Lakehead, Shasta Lake City, and Old Station. 

Data from the AirNow site.

Why do AQI sensor values vary so much over time, location?

Air quality can vary widely by location and time, according to Waldrop, who explains that Shasta County’s widely varied landscape creates a multitude of microclimates. That’s why, he says, AQI readings can vary rapidly from day to day, place to place, and hour to hour. Air pollution in Shasta County often moves like water, Waldrop said, because frequent winds from the north push it to lower elevations and down rivers, streams, and creeks. This pattern tends to move smoke into the city of Redding, essentially the lowest point in Shasta County, overnight, Waldrop says, which is why city residents often wake to heavy smoke during wildfire events.

Do hazardous air quality levels during wildfire events trigger federal or state systems to protect public health? 

Waldrop isn’t aware of federal or state monitoring being used to increase public education or resources during exceptional events like wildfires.

Has California’s focus on mitigating and adapting to climate change provided resources for those experiencing dangerous air pollution as a result of wildfire events?

California’s AB 836 provides funding for clean air centers, which could be utilized during hazardous air events to provide respite to those without access to other clean air resources, but Shasta County has not yet begun the process of developing those centers.  

Kerri Schuette of Shasta County Health and Human Services says for now the county’s recommendation is to utilize indoor public spaces like the library or mall to access clean air. During the school day, Waldrop says, schools can also function as clean air centers for children as most provide closed indoor spaces with good air filtration.

While Shasta County does not currently provide clean air centers or vouchers for air filtration devices, they are offering a limited number of N-95 masks to the public and also provide public education about the hazards of wildfire smoke via their website and social media. 

Overall, Waldrop says, for those who can, planning ahead to purchase masks and filtration devices is going to be important.  

“This is probably going to happen again, “ Waldrop said, referring to the hazardous smoke associated with wildfires,  “it’s happening more and more often.”  


How to Protect Yourself:

  • If possible, keep doors and windows closed whenever AQI is in the unhealthy range or above.
  • Use an air conditioning filter that’s MERV certified 13 or above, if you can. Change frequently.
  • Monitor AQI using the AirNow website or mobile app. Check AQI levels before any exposure to outdoor air as levels can change frequently over time and location.
  • Wear an N-95 mask if possible whenever exposed to hazardous air. N-95 masks filter out 95% of the dangerous particulate matter from wildfire smoke. 
  • When driving, keep windows closed and turn your air conditioning, if you have it, to recirculate, to ensure you’re not drawing in more smoke. 
  • Do not use a swamp cooler or whole-house fan to cool your home during hazardous air events. Swamp coolers and whole-house fans circulate outdoor air inside the house, contaminating indoor air. 
  • Use a CARB-certified indoor air filtration device if you can. Change the filters on your device outdoors as often as recommended for heavy use.
  • If you don’t have good air purification at home, set yourself up with a “clean room” that is closed and heavily filtered where you and your family can spend most of your time.

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