I Live in California. How Do I Know It’s Safe to Go Outside? - The New York Times

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Here in California, those of us lucky enough to escape the wildfires are battling smoke. We can’t always see our enemy, but we can smell it. For a while, the whole Bay Area reeked of rotting plants; experts suggested that a source was succulents burning along the Santa Cruz coastline. Some nights, there’s a rich, woodsy scent that reminds me of sitting on the beach around a campfire. But in the morning, the odor is more like stale cigarette butts. As I write this, the stench is of burning rubber and plastic.

At first, it’s an annoyance. But then the sinus headaches kick in, or the asthma, and the anxious lethargy that comes with staying indoors on a hot day with the windows shut tight. When will we be able to breathe again? To find out, many of us in the Bay Area have turned to a community-driven app called PurpleAir. Using OpenStreetMap and a worldwide network of 8,000 environmental sensors — mostly mounted on private homes — PurpleAir reveals the air quality in your neighborhood at any given moment.

It’s a straightforward and practical tool. The Environmental Protection Agency, university researchers, and popular weather services like Weather Underground all use PurpleAir’s data. But the app is also a harbinger of where “smart city” technology might take us. These days, most of us encounter such devices in the form of surveillance cameras run by law enforcement, or in the agile electrical grids managed by local utilities. Many of these systems raise concerns about who has access to vast amounts of data, often with little oversight.

PurpleAir suggests another possibility. These sensor networks are crowdsourced and run by ordinary citizens, and the data they collect can help individuals and communities understand how to live in a world turned upside down by climate change.

During fire season, I hit the PurpleAir website and check San Francisco every hour or so. Each sensor shows up as a circle on the map, with colors ranging from green for excellent air, to yellow and red for medium haze, and dark purple for air so dirty it can cause health problems. A couple of weeks ago, I bought a sensor of my own. It’s roughly the size and shape of a coffee mug, and I mounted it easily on a wall near my balcony. Other people mount them in backyards, just outside apartment windows, or on utility poles at intersections. They work by sucking in air, shooting it past a laser, and using a detector to count how many particles reflect the laser’s light. Put simply, the more particles there are, the worse the air.

Though it’s usually obvious from the smell when the air is bad outside, PurpleAir shows me when things are starting to improve. As breezes come off the Pacific in the afternoon, a color gradient washes over the city. Starting at Ocean Beach, the red sensors turn yellow, then green. Eventually the wave of yellow sweeps over the hills of Twin Peaks and into the Mission and downtown areas to the east. Often, by late afternoon, the city is a vivid green.

I’ve never been so aware of the winds and microclimates around me. It took a disaster and a high-tech sensor network to bring me closer to the natural cycles of my environment. And that’s exactly the point.

Adrian Dybwad, an engineer and the founder of PurpleAir, started tinkering with air quality sensors five years ago. The gravel mine next to his house in Utah was filling the air with so much dust that it turned the sky red. Geneva Rock, which owns the mine, announced plans to expand. Mr. Dybwad knew it couldn’t be healthy to have so much dust in the air, and he wanted an objective measure of the pollution he and his neighbors were inhaling. After he gave away roughly 80 of the sensors, people began to ask about buying them. And so PurpleAir was born.

Mr. Dybwad said most of his customers are driven by health concerns. People with asthma use PurpleAir to figure out whether it’s safe to go outside. For agricultural workers, air-quality data can be used to determine when it’s safe to spend hours picking fruit outside — and when to stay home or wear fitted N-95 masks. When I consider whether to go outside, PurpleAir is what stands between me and potential lung disease. We used to rely on the government to warn us about dangerous conditions, but with a president who denies climate change and has ordered deep budget cuts at the E.P.A., we have to rely on each other.

We’ve entered the age when good citizens help their communities stay healthy by sampling the air with sensors and making that data public. In many ways, PurpleAir feels like an inversion of the troubled social app Nextdoor. Though it was supposed to be a place where neighbors got to know each other, Nextdoor was quickly overrun with bitter disputes and racist accusations about “undesirables” who loitered on corners.

Communities with PurpleAir sensors aren’t focused on what their neighbors are doing, so much as they are on the climate that we all share. Steve Mann, a University of Toronto engineer, calls this “sousveillance,” or observation from below. A cellphone camera can be a sousveillance device to document police violence. An air-quality sensor can be a sousveillance tool to record how industry menaces many life-forms on this planet, including humans. At its best, sousveillance can help those who use it to demand accountability for pollution and fire hazards in their communities.

Still, as Mr. Dybwad explained, technology is no replacement for good citizenship. He invented the first PurpleAir sensor to stop the mine near his home from expanding, but the sensors themselves didn’t help much. They aren’t good at detecting dust from gravel pits, which tend to be much larger than smoke particles. Instead, Mr. Dybwad said, “We’ve had more success with people showing up at City Council meetings to get people aware of what’s happening with the mine.”

The sensors got the ball rolling, but activism sealed the deal. If you want to fight air pollution in your community, he advised, “Go to the City Council. That’s how we did it.”

Annalee Newitz (@annaleen), a science journalist and contributing Opinion writer, is the author of the forthcoming “Four Lost Cities: A Secret History of the Urban Age.”

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I Live in California. How Do I Know It’s Safe to Go Outside? - The New York Times
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