Health & Medicine

Do you live on the Nipomo Mesa? Here’s what you need to know about air quality

If you live on the Nipomo Mesa, you’ve probably seen a haze of dust on windy days. Did you know it’s a health risk?

While the air is generally clean in San Luis Obispo County, there are often areas of the Nipomo Mesa where the air is unhealthy for a few hours at a time because it contains particulate matter.

That can cause frequent coughing and congestion, and more serious problems for children, seniors and people with existing heart and lung issues like asthma.

On those days, the county Air Pollution Control District and Public Health Department send out an alert.

On Sept. 17, for example, an alert said that “blowing sand and dust is forecasted to occur from 11 a.m. to 7 p.m., with the dust forecasted to peak from noon to 6 p.m. Very sensitive individuals such as infants, as well as children and adults with existing respiratory or heart conditions, may experience adverse health effects during blowing dust periods.”

There are simple ways to protect your family when that happens: Sign up to receive air quality alerts from, keep an eye on the Air Quality Index at, and then limit exposure to outdoor air when the air quality is less than good.

Particulate Matter - Utah Health Department.png
Particulate matter or particle pollution is a combination of solid particles and liquid droplets that are small enough to reach the small airways in the lungs, potentially causing damage. Image by the Utah Department of Health

What is particulate pollution?

Particulate matter — or PM for short — contains tiny particles in the air that can be inhaled deep into the lungs. It can come from agriculture fields, construction sites, dirt roads, wildfire smoke — or dust from sand dunes.

These particles are tiny enough to travel past your body’s defense system in the upper respiratory system and get into your lower respiratory system. There, they can reach the small airways of your lungs that are important for oxygen exchange.

The state of California has set standards for what is considered unhealthy levels of PM exposure over a 24-hour period.

Permanent Air quality monitors on the Nipomo Mesa show that the air quality in some areas sometimes violate those standards. Those monitors are approved by the U.S. Environmental Protection Agency and managed by the Air Pollution Control District.

The level of particulate pollution measured at the Cal Fire station on Willow Road on the Nipomo Mesa violated state standards on 97 days in 2017 and 47 days in 2018. By comparison, air quality in Paso Robles violated state standards two days in 2017.

What we know about air quality on the Nipomo Mesa

Dirt roads, fields and construction sites all contribute particulate matter in rural areas.

The Air Pollution Control District says that the highest concentrations of particulate matter are blown in a plume of dust that wafts downwind from the riding area at the Oceano Dunes across the Nipomo Mesa inland toward Santa Maria. That happens most when strong winds blow from a west-northwest direction.

Air quality monitors show the plume is thicker closer to the dunes and dissipates as air moves downwind to the southeast. Dust events are also seen near downtown Oceano.

In general, the air is clear in the morning. Dust moves when the wind picks up in the afternoon into early evening.

Strong winds are most frequent in the winter and spring. But gusts can bring wind-driven emissions any time of year.

“Those are the times when the air quality is really bad and you want to limit your activity,” according to county Air Pollution Control District officer Gary Willey.


Do you live, work or go to school in the plume?

Each dust event is different depending on the direction of the wind, but the Air Pollution Control District has identified a general shape where particulate matter is the worst during a dust storm.

Analysts determined the shape of the plume and found out which areas experience higher levels of PM by studying data from 23 temporary monitors placed around the Nipomo Mesa and Oceano in 2012. As a result, the APCD created a forecast zone map to identify areas that are likely to see elevated levels of dust in high winds.

Search an address in relation to the plume using an interactive Google map by clicking here. Once you’ve identified what color area you live in, you will know which air quality monitor on most closely align with where you live.

Areas in red align with the Nipomo-CDF monitor (county fire department), areas in orange are closer to the Nipomo-Mesa2 monitor and peach is closer to Nipomo-NRP monitor (Nipomo Regional Park).

Areas in green that are near to the border of the peach area may see elevated dust levels during certain wind events. In general, green areas are more closely correlated to the San Luis Obispo monitor.

Sept 17 air quality.JPG
Air quality data from monitors around San Luis Obispo County can be found at This screenshot captured Sept. 17, 2019, around 4 p.m. shows that levels of PM10 and PM2.5 measured much higher at the Nipomo CDF station (on Willow Road). This is common during strong wind events in South County.

What is the health risk?

Particle pollution can affect anyone. If you’re a healthy adult, you might get a cough or feel congested. If it lingers for awhile, if you get out of breath or if you have chest pain, you might want to see a doctor.

People most likely to experience serious health effects during high PM events are babies and children, older adults and people with existing heart or lung issues like asthma.

“Areas that are known to have higher particulate matter are known to be associated with higher than normal respiratory issues. We see that in terms of respiratory admits to the hospital or people who are needing respiratory treatment from their physicians,” according to Stephen Szabo, director of cardiopulmonary and respiratory services with Tenet Health.

Stephen Szabo, Director of Cardiopulmonary / Respiratory Services with Tenet Health, the owner of Sierra Vista Regional Medical Center and Twin Cities Hospital. David Middlecamp

Most air pollution research and health standards are based on exposure to high levels of particulate matter over a 24-hour period of time or a year. Air quality on the Nipomo Mesa is often a problem for a few hours a day.

There is some research about brief exposure to high levels of particulate matter, but not a lot.

The Tribune spoke with several medical researchers and doctors and found that the following information can by applied to the air quality trends seen on the Nipomo Mesa.

Children have a higher risk of health effects because they are active outside for longer periods of time than most adults and because their lungs are still developing.

Increased particulate matter correlates with an increase in asthma attacks, bronchitis, chronic cough and even common cold. Some research found PM exposure makes allergy symptoms worse.

A health study in southern California that tracked 1,759 children from 1993 to 2001 found that kids who grew up in more air pollution are more likely to have reduced lung growth, according to the American Lung Association.

Pregnant women exposed to particle pollution are more likely to experience pre-term labor, according to a study in California from 2001 to 2008 published in Environmental Health Perspectives. In addition, exposure to particle pollution can affect a baby’s lung development even before birth.

Older adults and those with existing conditions exposed to particle pollution can experience aggravated heart disease and stroke, lung disease like chronic obstructive pulmonary disease and diabetes, according to the Centers for Disease Control.

Even short-term exposure to fine particle pollution has been linked to premature death, heart attacks and chronic bronchitis. A 2001 study of 772 patients found that increased concentrations of fine particles in the air may elevate the risk of heart attacks within a few hours or within one day after exposure.

Sung Kim walks Toby in the eucalyptus trees at the Trilogy development on the Nipomo Mesa. Dust can be seen obscuring the blue sky, on a day that the San Luis Obispo County Air Pollution Control District issued a blowing dust alert. David Middlecamp

How do I protect my family from the health risks of dirty air?

The first thing to do is to find out when the air quality is less than good.

When the air quality is bad, public health officials recommend that you avoid strenuous outdoor activity, stay indoors and close all the windows and doors. You should also turn on any air filters, and set any air conditioning unit to recycle indoor air. Sensitive people may consider leaving the area.

If your job prevents you from staying indoors when the air quality is bad, consider using an N95 mask approved by National Institute for Occupational Safety and Health. These masks will not help you if they are not fitted properly.

Here are a few ways to check the air quality:

For more information, contact the county Air Pollution Control District at 805-781-5912 or the county Public Health Department at 805-781-5500.

If you experience chest pain or shortness of breath, or if your child has a persistent cough, please consider seeking professional medical assistance.

Monica Vaughan reported this story as part of her University of Southern California Annenberg Center for Health Journalism 2019 California Fellowship with engagement support from the Center’s interim engagement editor, Danielle Fox.

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Monica Vaughan reports on health, Cal Poly, San Luis Obispo County, oil and wildlife at The Tribune. She previously covered crime and justice in the Sacramento Valley, is a graduate of the University of Oregon journalism school and is a sixth-generation Californian. Have an idea for a story? Email: