Whistle-Sized Device Samples Ozone

Ozone is both a boon and a bane. High in the atmosphere, it protects the Earth from harmful ultraviolet rays, but down near the planet's surface, it is a notorious pollutant which damages the respiratory tract and ruins trees and crops.

According to School of Public Health Associate Professor of Environmental Sciences Peter Koutrakis, the Environmental Protection Agency (EPA) currently monitors ozone levels in major cities with large bulky instruments each costing about $10,000.

But Koutrakis and a team of fellow Harvard researchers have invented a handy portable device for measuring levels of ozone that is not only convenient to use, but makes accurate readings at a fraction of the price.

EPA samplers measure around 3x3x3 feet and cost near $10,000, whereas the Koutrakis sampler is the size of a whistle and costs only $40.00.

Koutrakis got the idea for the sampler upon discovering that ozone combines with nitrite ion to form nitrate ion, a finding recently published in the journal Analytical Chemistry.

The device contains a nitrite-coated filter whose surface molecules are altered when exposed to ozone, thereby allowing it to accurately measure ozone levels.

"Our sampler lets us go out and measure thousands of people a day to get the distribution of human exposure to ozone and understand what factors affect human exposure to this pollutant," says Koutrakis.

Although a number of efforts have been directed at reducing the levels of ozone in the environment, daily measured concentrations often still exceed the National Ambient Air Quality Standard.

"Two thirds of the people in the United States live in areas that don't satisfy national air quality standards," says Koutrakis. "There is a lot of pressure on the EPA to reduce the ozone in the atmosphere."

By performing exposure and assessment studies, says Koutrakis, the scientific and regulatory community can hope to understand the extent of exposure and attempt to reduce levels.

The EPA currently places large monitors in the center of major cities in order to regulate ozone levels.

"We don't believe that this represents the total exposure," Koutrakis says.

Koutrakis says distributing his new samplers in microenvironments high in ozone, such as in airplanes, would yield more accurate measurements.

The sampler's small size did not compromise its accuracy, says Koutrakis, since the readings are within 10 percent accuracy.

Ten percent is "more than enough," says the professor, "because the concentrations of ozone change dramatically as you move from environment to environment."

In Use at Universities

Koutrakis said the sampler is currently in use by universities and research groups developing statistical models for measuring exposure, and to let the EPA know the extent to which their current measurements are inaccurate.

The team is presently working on developing an active sampler which would force air through a filter rather than base its measurements on passive gaseous diffusion. An active sampler would be more sensitive than its passive counterpart by collecting a good sample in less time, according to Koutrakis.

Ozone, says the scientist, has been shown to have detrimental effects on the health of individuals as well as on the environment.

"We have found through epidemiological and clinical studies that acute or chronic exposure to ozone has adverse effects on the respiratory medium," says Koutrakis. "Ozone is an ecological threat because of its damage to crops, trees and even paintings."