Here’s how many times air quality standards have been violated on the Nipomo Mesa

Air quality significantly improved on the Nipomo Mesa over the past year. That’s good, but it doesn’t mean the problem has disappeared.

Violations of state air quality standards continue, which is why the county Air Pollution Control District continues to press State Parks to get a handle on dust emissions drifting from its Oceano Dunes off-highway vehicle recreation park, located near the Nipomo Mesa.

The issue is harmful, microscopic dust particles classified as PM (particulate matter) 10 — which means they are 10 microns or smaller.

To get a sense of the size, an average human hair is 70 micrometers in diameter.

All areas of San Luis Obispo County have days when PM 10 standards are violated — during wildfires, for example — but the number of violations are generally down in the teens, according to county APCD chief Gary Willey, and it’s usually from an event that’s short-lived.

Only on the Nipomo Mesa has the number of violations been so high.

“It’s the only really significant air quality issue we have in the county, by far,” said Willey.

Here’s a look at how the number of air-quality violations varies by three Nipomo Mesa locations:

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