Environment & Science

How dirty is the air right outside your door? Now you can afford to find out

Smog blankets downtown Los Angeles. New low-cost air monitors allow people to know what air pollution is like not just in their city, but right outside their door.
Smog blankets downtown Los Angeles. New low-cost air monitors allow people to know what air pollution is like not just in their city, but right outside their door.
Photo by Ben Amstutz via Flickr Creative Commons

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Dominic Massetti’s house is sandwiched between a power plant and the 405, but despite that, he didn’t think much about air quality until this past summer. That’s when he read a study that found that elderly people who breathe even marginally polluted air were 7 percent more likely to die early. He realized that was him.

He wanted to know how polluted the air was outside his front door? It’s a question that, until the recent advent of low-cost air monitors, he would not have been able to answer.

In Massetti’s neighborhood, the Leisure World retirement community in Seal Beach, the closest air monitors maintained by the South Coast Air Quality Management District were 13 miles away. There weren't any local data. So he called up the agency and asked it to install a monitor where he lived.

The PurpleAir monitor on the roof of the KPCC studio in Pasadena.
The PurpleAir monitor on the roof of the KPCC studio in Pasadena.
Emily Guerin/KPCC

He remembers being told, “They’re the size of a truck, and they cost $250,000." But he learned the agency was doing a pilot program to test out a new type of cheap, softball-sized air sensor. Did he want to be a part of it?

Massetti said yes, and now he’s attaching 50 monitors to walls around Leisure World. He thinks it will completely change the way he and others communicate with the SCAQMD about air issues.

“You see people get up at the podium and complain about air quality and their health. But they do it in qualitative ways,” he said. “We will be able to do it in a quantitative way, and it won’t be as easily ignored.”

The greater Los Angeles area has some of the worst air quality in the country. It consistently ranks No. 1 on the American Lung Association’s list of cities with the worst smog and is within the top ten for fine particulate matter: diesel soot, vehicle exhaust and dust. 

The SCAQMD maintains a network of 38 monitors to track these pollutants, but their purpose is to provide regional air data – not to tell you what the air is like outside your front door or at your kids' school. Enter the new breed of low-cost air sensors. 

Adrian Dybwad makes some of the most popular ones, called Purple Air. There’s currently a network of 700 of them around the country, all uploading data to a public website. KPCC even has one!

For more information about the air quality at a given location, click on the circle with the number inside it. Or zoom out to see what the air quality is like in all of Southern California.

Dybwad dreams of a day when his sensors are not just used by curious people but by regulators to hold polluters accountable.

“Our aim is to pepper the area with so many sensors that you can’t but see where (the pollution) is coming from,” he said. “And let’s make those people that are producing the pollution responsible for reducing it or responsible for removing it.”

But air quality officials are wary of using the low-cost sensors for regulatory purposes quite yet. That’s because in order to be used for enforcing state or federal law, an air monitor has to be extremely accurate. The SCAQMD has a lab where it tests the sensors alongside its own, EPA-approved equipment. The agency has tested 40 models so far. Some did really well, like Dybwad’s Purple Air But some failed horribly, which worries Matt Miyasato, the SCAQMD’s deputy executive officer for science and technology advancement.

“If the public gets ahold of that, that could be quite scary, not knowing if they’re in danger or not,” he said.

The last thing Miyasato wants is people like Dominic Massetti coming to meetings to present alarming air data, and then have that data be wrong. That’s why the agency publicizes the results of its tests. It’s a little confusing, but pay attention to the Field R2 and Lab R2 columns. The closer the R2 value is to 1, the more accurate the sensor is.