Each pair of filters is then 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. If the kid is at home, a Bluetooth beacon informs the sensor and it switches valves accordingly. When the sensor loses the signal, it then must decide between the other two locations. An inputted schedule helps it determine when to switch to school mode. (This is overridden if, for example, a kid is home sick and the Bluetooth signal from there is picked up.) During all other times, a subject's location is determined using global positioning system technology (GPS). "Someday, when GPS gets even better, we can do all the switching based on it," Chillrud predicts. And, 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. "As all these samplers get smaller and smaller, compliance becomes a big issue," Chillrud explains. "Before the question was, 'Do you want to carry a big backpack?' Now, it is, 'Do you carry it the right way?'" 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.
Sensing new policy
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 analyzed 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," NIEHS's Balshaw says. "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, Cowin suggests, "then we could better understand the risks and add that into the equation of what we need to do about it. In setting policy, there are some things we have control over. But you need to balance your possible actions against what you really see."
The same goes for an individual's decisions. Whereas it is unethical to strap people down and expose them to air pollution in a lab, Cowin points out that subjects will essentially do it to themselves: "They'll stand behind a bus for 20 minutes chatting." With a smart sensor, he adds, we could decipher what triggered an asthma attack: "Were they 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.