Air district accused again of misinformation regarding Oceano Dunes


For more than a decade, San Luis Obispo County’s Air Pollution Control District has claimed that 100% of the dust particles blowing on the Nipomo Mesa are the result of off-roading at the Oceano Dunes.

It is 100% sand dune dust (mineral dust) from the Oceano Dunes, the APCD reported.

It causes cancers, and lung and kidney disease, the APCD reported.

It can be stopped by reducing vehicle use on the dunes, the APCD reported.

“The APCD has been investigating the source of the high particulate matter concentrations on the Nipomo Mesa for the past decade,” the APCD says on its website. “Several studies performed by the APCD in the Nipomo Mesa area have shown the source of the elevated particulate matter pollution to be windblown dust from the open sand areas of the Oceano Dunes State Vehicular Recreation Area.”

In response to the APCD’s claim, the state of California has spent more than $22 million to reduce dust from the Oceano Dunes, in an attempt to protect the health of people living on the mesa.

However, the prestigious Scripps Institution of Oceanography analyzed the particulate and determined only 14% of the particles blowing on the mesa consist of mineral dust. In other words, State Parks is not to blame for bad air quality on the mesa.

The study determined particulate concentrations are highest during high wind conditions, even when off-road vehicles were banned from the dunes during the pandemic. Researchers also determined the mineral dust blowing on the mesa is more likely caused by natural forces such as wind, than off-road recreation.

Scripps’ findings also call into question the validity of all data collected from the monitoring instruments used by the APCD and many other air districts nationwide.

After 10 years of warning Nipomo residents of the dangers of silica dust, in 2017 the APCD decided to run tests for silica in the air. The testing refuted the APCD’s earlier claims, concluding the dust blowing from the dunes did not contain dangerous levels of crystalline silica.

Even so, in 2018, State Parks entered into a stipulated order of abatement with the APCD. The order requires the state to reduce wind-blown dust, specifically dust particles that are 10 microns or less in diameter, on the Nipomo Mesa by 50%. Despite agreeing to the various terms in the order, State Parks still denied that off-roading causes the dust on the mesa.

After more than a decade of asserting off-road vehicles at the Oceano Dunes are responsible for 100% percent of the dust blowing on the mesa, the APCD has admitted it never analyzed the particulates for mineral dust content.

Despite Scripps’ findings and the APCD’s admissions, State Parks continues to acquiesce to APCD demands that the park reduce dust blowing on the dunes by 50%. State Parks has covered more than 200 acres of dune sand with hay, vegetation or orange plastic fencing in an effort to reduce wind-blown dust.

During the past 12 months, State Parks has spent almost $3 million attempting to comply with the APCD’s demands.

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3 Comments about “Air district accused again of misinformation regarding Oceano Dunes”

  1. tedschade says:

    The air quality standard most often violated in the area of the dunes is the PM10 standard. These 10-micron particles are most often associated with blowing dust. The Scripps study focused solely on PM2.5, particles one-forth the size of PM10 and most often associated with combustion sources like fires and vehicle exhaust. The PM2.5 standard is rarely violated at the dunes. The Scripps scientist looked at the wrong pollutant! It would be like studying dolphins and using the study to make conclusions about humpback whales. The study’s methods and conclusion are deeply flawed. (I was a dust scientist for 25 years.)

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