Bicyclists strap on monitors to measure Twin Cities air quality

Bicyclists are used to getting left in the dust, but now a group of pedaling Minneapolis staffers is collecting it for science.

Air-quality sensors are hitting the streets in Minneapolis and St. Paul this summer as local regulators experiment with cutting-edge, low-cost wearable devices that could illuminate how pollution varies across cities and neighborhoods. They hope those readings reveal more ground-level detail than the large, regional air monitors that report broader trends across the metro area and the state.

"People want a block-by-block ranking of air quality," said Cassie McMahon, environmental research scientist with the Minnesota Pollution Control Agency (MPCA). "And that's logistically impossible to do with our traditional monitoring equipment."

Several Minneapolis employees on bicycles will strap devices to their arms and pedal to all corners of the city testing the readings against a high-end monitor. And in a separate project, the MPCA will distribute about two dozen similar devices to a group of people in St. Paul's south St. Anthony Park area, giving residents there license to experiment with collecting localized air quality data.

Wearable air pollution monitors got a test at the 2015 State Fair. The highest readings? The smoky stretch of Judson Avenue where charbroiled pork chops on a stick are served up. The monitors, which are made by a variety of companies, link with smartphones to report and map data in real time.

Dan Huff, Minneapolis' director of environmental health, said they could ultimately be strapped to citizens to measure their exposure while cooking at home, for example, or on the bus to work.

"A dream study would be having people with asthma wear these," Huff said, noting that Minneapolis has the highest asthma hospitalization rates in the state. If someone noticed symptoms flaring up, they could try to pinpoint the cause. "Was it because there was an increase in [particulate matter], or was it something completely different?"

The wearable devices are not as accurate as the 53 large sensors that the MPCA uses to determine if regional air quality is meeting federal standards. Those monitors, typically atop buildings, cost more than $150,000 apiece to install, however, while wearable sensors cost several hundred dollars.

Air quality in the Minneapolis-St. Paul area is relatively good compared to other major U.S. metropolitan areas, according to data from the Environmental Protection Agency. The two major factors used to determine the air quality index are fine particulates in the air and ozone, which is created by a chemical reaction and tends to float downwind of the central cities. The new wearable devices being tested this summer monitor only particulates.

The wearable sensors may pick up on localized variations where the larger rooftop sensors cannot. The volume of particulates, often created through combustion, is generally worse close to major roadways. Air quality can also be affected by wildfires raging upwind, winter weather that traps pollutants or very hot summer days that accelerate ozone production.

"You're relying on [large monitoring stations] to give you kind of an average sense of what the air pollution levels are like," said University of Minnesota Professor Dylan Millet, who specializes in atmospheric chemistry. "But in reality they're going to vary tremendously depending on whether you're standing on a street corner in downtown Minneapolis to if you're out in Eden Prairie, for example."

While the air in the Twin Cities is not akin to that in Beijing or Los Angeles, Millet said there is evidence of negative health effects from pollution in the metro area. Fine particulates can cause cardiovascular and respiratory diseases, infections and cancer.

Three Minneapolis employees, led by Health Department staffer Ahmed Hashi, took the wearable air monitors — secured with Velcro straps sewn together at a Somali mall in south Minneapolis — for a test spin through northeast Minneapolis one recent morning.

They intend to take measurements over 11 days on predetermined routes, measuring morning and afternoon rush hours on both busy and residential streets. The findings will be compared against large monitors temporarily stationed at their starting points. If it goes well, Hashi imagines more riders and sensors in the future.

"You can kind of have real-time decisionmaking and say, 'Hey I'm going to avoid this area, there's a lot of pollution,' " he said.

It's not the first time someone has measured air pollution on a bike in Minneapolis. In 2012, a graduate student at the University of Minnesota pedaled around with a larger monitor on wheels. The research showed the extent to which air pollution is higher on busy arterial roads vs. calmer local routes or off-street bike lanes.

The city's health department is also making strides pinpointing hot spots of other harmful compounds in the air. It recently conducted a two-year study using 120 canisters placed around the city, which found potentially harmful concentrations of four chemicals in various areas. A full report is expected later this year.

The MPCA experiment in south St. Anthony Park is more open-ended, geared toward learning more about how residents might use low-cost sensors while letting them test their own hypotheses.

"They can bring it inside and outside of their home," McMahon said. "We're not telling them what they can and can't do with these instruments."

Eric Roper • 612-673-1732

Twitter: @StribRoper