The San Diego Air Pollution Control District monitors air quality across a 4,000-square-mile region where 3 million people live. Over all of that space–-in all of that air—the county has only about 10 monitoring stations checking for pollution levels. When computer scientist William Griswold first heard this, he says, he was shocked.
Pollution isn’t as monolithic as we often think when we picture smog hovering over a city skyline. It dissipates in the atmosphere, Griswold says, in a very non-linear way. The tailpipe emissions you inhale at one intersection may be dramatically different from the next block over. And so if you really want to know what you’re breathing, you need something more localized than government data can give you. You need to be your own monitor.
"The averages reported by the air quality district are accurate as an average," says Griswold, a professor at the University of California at San Diego. "But what you experience during the day are exposures well below that, and well, well above that. If you’re asthmatic, those peak exposures can trigger an episode."
Griswold and other researchers at UCSD have designed a solution: a portable air-quality sensor that relays live data to your smartphone (and, from there, to a university server that aggregates all of the results). The "CitiSense" model leverages portable sensing to enable individuals to track their own exposure. But the idea also creates crowdsourced research opportunities for scientists who could gather a lot more data through a hundred cell phones than public agencies are currently doing with a handful of air-monitoring stations.
"It’s not just a shift in technology," Griswold says. "It’s a shift in who is taking charge of the matter. Everyday citizens can collect this data and think about it for themselves, they don’t have to wait for the government to step up. Especially in these difficult budgetary times, it’s not really reasonable to think the San Diego air quality district is going to put out a thousand sensors."
UCSD has so far put out 20 of them, with an assembly cost of about $1,000 each. The academics aren’t planning to go into mass consumer production, although the work they’re doing may inevitably lead others there. "Research," Griswold says, "is really a rapid prototype of the future." He predicts that in a decade, you may even have this air-quality sensing technology directly on your cell phone.
For now, the researchers have produced a sensing board in a bulky plastic box, printed on a 3-D printer, that’s about the size of your hand. Via Bluetooth, it feeds the data to your cell phone, where a user-friendly interface displays the readings of ozone, nitrogen dioxide, and carbon monoxide with a color-coded EPA score that cuts to the chase: Instead of giving you parts-per-million scientific jargon, the screen gives an air-quality score on a scale from good to moderate to unhealthy to hazardous. As the prices of such portable sensors drop, and their battery life rises, such tools could soon become affordable on the mass market.
The researchers have already sent them out for trial runs with commuters, faculty, and students at the university. Those trials revealed that bikers and pedestrians were often exposed to the most pollution, an ironic punishment for people trying to commute in the most eco-friendly way (drivers not only benefit from cabin filters, they also simply move through pollution faster). Many of the users, Griswold says, were surprised to realize how dramatically their exposure varied over the course of a day. Many changed their commuting routes or behavior as a result, suggesting that such personal air monitors might have appeal even beyond specialized populations like asthmatics.
The whole idea also has the potential to change how you think about your cell phone. "We’re sort of used to mobile phones being a distraction—they take you out of your environment," Griswold says. "The thing we’re most afraid of is a driver talking on his cell phone. But what this technology did was it changed the mobile device into something that re-engaged you with the environment rather than disengaging you from it."