This Should Shed Some Light On Pollution's Ill Effects

Ever stricter clean-air laws mean utilities and state and local governments must carefully track air emissions for Environmental Protection Agency review. Current systems measure only a few contaminants. The EPA is testing a spectroscopy-based system, OPSIS, that charts 20 chemicals at once.

Here's how: As a narrow light beam travels through the air, each gas absorbs light in a specific wavelength. The telltale wavelength for sulfur dioxide, for example, differs from that for ozone. With OPSIS, a spectrometer automatically determines the concentrations of pollutants by studying how much light is absorbed at each wavelength.

In addition, the beam can scan either a small area to measure smokestack emissions or a wider swath of up to 1.5 miles to chart regional air quality. Asea Brown Boveri Inc., which is marketing OPSIS to U.S. utilities, says the system will save up to 85% on testing and operating costs. The EPA is considering using OPSIS as a basis for new regulations that would require measuring more pollutants over a broader area.