How clean is the air outside your home, local school, or athletic field?
You’ve undoubtedly heard those news reports — probably several times this summer: It’s a bad air-quality day, so stay indoors as much as possible and avoid strenuous activity if you must go out. But you may have wondered if that really applies to you, particularly.
When the government issues the information that prods air-quality alerts, it's based
on readings from several air-monitoring stations set up around a city. These
pollution-sensor centers are anchored in place, often fairly high off of the ground, which
puts them well above the intake zone of your sniffer and mine.The state
then takes readings from several stations around town and averages them to
suggest what community residents might encounter.
The problem here: None
of us breathes average air.
We suck in the idiosyncratic mix of pollutants that exist at some particular time and at the precise place we happen to be — sitting beside a secluded stream, walking along a busy highway, enjoying the hammock in our backyard a quarter-mile from some manufacturing plant, or biking past a recycling center. It’s a good bet that the air is considerably and reliably dirtier in some parts of town — or rural regions —than in others. Yet stationary pollutant monitors can’t identify where these spots are.Which is why Akos Ledeczi is designing small and eminently portable air samplers — ones that street cops could snap onto their belts while patrolling their beats, couriers could strap onto their bikes, or mail trucks could carry on every dashboard. Each of the smaller-than-a-sandwich size devices would collect air-pollution data about once a minute and temporarily store it on a flash drive. Whenever the units fell within range of a Bluetooth-enabled device in the system’s network or wireless relay station, they’d spit out their data.
a global-positioning-satellite chip, each sensor-packed device knows precisely
where it is, and links those coordinates to the air-sampling data collected
from each spot, explains Ledeczi, a scientist at Vanderbilt
would be to deploy an army of these things to meander throughout a community,
collecting up-to-the-minute, street-level data on air quality.
Right now, however,
this system is “a work in progress,” Ledeczi acknowledges. Only five prototypes
exist. Still, they’ve been spitting out air-quality readings as they’ve been ferried
by cars throughout
Environmental agencies have deployed their stationary existing air-sampling stations relatively sparsely. For
example, just 10 stations collect air-quality readings for
more useful clues to how risky outdoor conditions were if such data were issued
separately for each pollutant, by neighborhood (perhaps superimposed on a local
map) and updated hourly. And that’s what Ledeczi’s system hopes to make
that the Vanderbilt units are not ready for prime time: The readings of their gas
sensors will, for any given pollutant concentration, fluctuate with
temperature. If all of the units from a given manufacture fluctuated comparably under given conditions,
an onboard computer chip could account for this, based on the temperature
sensor’s data. However, the Swiss firm that made the Vanderbilt system’s
sensors hasn’t published data on how to do this, which Ledeczi says may
indicate there is substantial variability in the sensitivity of its units.
size and costs down, Ledeczi’s devices also aren’t all that discriminating. They
can measure temperature, humidity, ozone, nitrogen dioxide, carbon monoxide,
and some general composite mix of volatile organic chemicals, also known as VOCs. But they can’t tell you, for
instance, what the specific concentrations are for VOCs of particular interest,
such as the carcinogens benzene and benzo(a)pyrene.
would seem that these or next-generation portable monitors should soon be able to offer the
ability to glean a fairly accurate picture of air quality down to the neighborhood
level. The down side: Consistently poor-quality air could result in lower
property values within a couple-square-block area. Then again, this community and every
other neighborhood would also have rock solid ammunition for putting pressure on individual
polluters and the local government to clean up our air.
The work by Ledeczi’s team has been supported by a gift from Microsoft Research.
Mobile Air Quality Monitoring Network. Institute for Software and Integrated Systems. Vanderbilt University. [Go to]
Ledeczi, A. 2008. Mobile Air Pollution Monitoring Network. Workshop on Environmental Sensing Networks. Johns Hopkins University (Sept. 5). [Go to]
National Web Access to Air Quality Data. [Go to]