Pocket-size pollution sensors monitor personal environment

Environmental health scientists have grown increasingly interested in personal air pollution tracking in recent years. They realise that bringing monitoring down from the rooftops—where devices have breathed cities' concoctions of exhaled pollutants for many years—can help to identify the variability in exposures among people as well as during an individual's day-to-day activities. Average particulate matter concentrations across regions, for example, rarely reveal the specific air particles people breathe in any given location.

"The problem is, not many people live on rooftops. Most people live in floors as you go down, and walk about on city streets, and get around by cars, subways or buses," says Steven Chillrud, an environmental geochemist at Columbia University's Lamont–Doherty Environment Observatory. "So, if you really want to know what people are exposed to, you need to monitor them." This is especially true of children. "They get exposed to stranger dust in half an hour of playing than you or I would get in an entire month," says James Cowin of the Pacific Northwest National Laboratory in Richland, Washington.

So, this fall, dozens of nine- and 10-year-olds will be set loose on the streets and in the schools of New York City with new monitors co-developed by Chillrud, Cowin and their respective teams, each device featuring technologies designed to pinpoint not only what children are exposed to, but when, where and for how long.
Chillrud is one of eight grantees currently refining personal airborne pollution sensors as part of the National Institute of Environmental Health Service's (NIEHS) Genes and Environment Initiative—a project aimed at gaining an improved understanding of how genetic factors and environmental exposures influence human disease.

Traditionally monitors able to assess individual exposures had been housed in backpacks, weighing up to three kilograms which limited research participants. Chillrud and Cowan have now developed a new monitor that is little bigger than a cell phone and much quieter compared with earlier models. The prototype houses six pollution nets: three for the collection of black carbon and three for single particles, both prevalent in urban air and suspected hazards for children's health. Each pair of filters is designated for one of three key locations frequented by children: home, school and outdoors (or commuting). And the smart sampler automatically knows where it is at all times. As other technologies continue to improve, further shrinking of the sensor is planned, along with real-time black carbon and particulate matter monitoring.

Although the handheld device is easier to wear than a backpack, it is not problem-free. Measurements could be significantly off if the device is hooked to a belt, put in a purse or backpack, or even covered up by a winter coat. "There are lots of places they can go that we don't want them to be," Chillrud says. But with the help of motion sensors and a specially designed vest, they hope to keep them in the right place.

If all goes well in the project's validation stage, the sensors will soon be dispatched in the field with 30 asthmatic and 30 nonsufferers, a subset of several hundred kids that have been studied by researchers since they were in the womb—when their pregnant mothers wore the original backpack monitors. These kids will also be keeping symptom diaries and undergoing clinical assessments; the filters recording their exposures will be analysed in the lab. If a physical effect is seen, the researchers can go back and track exposures. Together with the airborne offenders that get caught by the filter, tracked locations can also lend valuable clues: Were they walking along a busy street? If so, it's likely automobile traffic. Were they in the house—in the kitchen? Then it could be cooking grease.

If researchers could correlate one to one what people are exposed to and their health effects, they could better understand the risks and add that into the equation of what needed to be done about them. With smart sensors it may be possible to decipher what triggered an asthma attack: standing behind a bus or Uncle Henry's smoking cigarette?" An answer may very well help defuse a serious health problem in the subject's future.

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First Publishe September 2009

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