Inhaling your food--and its cooking fuel.

A federal study finds that cooking without a working exhaust fan can flood the air of a typical house with ultrafine pollution-particles less than 0.1 micrometer in diameter. Recent investigations by other scientists have linked such ultrafine particles, which can be inhaled deeply into the lungs, to serious breathing and heart problems (SN: 8/2/03, p. 72). No one has yet established what amount of this pollution is hazardous.

With the help of researchers from the National Institute of Standards and Technology in Gaithersburg, Md., Lance A. Wallace of the Environmental Protection Agency in Reston, Va., rigged his house with sensors and recorded airborne particles every 5 minutes for 18 months. To maximize cooking pollution, he disabled his gas ranges exhaust fan, while rigging another fan to circulate air year-round throughout the home's ductwork.

During cooking, kitchen concentrations of ultrafine particles were initially about 10 times as high as those elsewhere. Within 30 minutes, however, the particles had spread fairly evenly throughout the house, and the concentration remained elevated for 2 to 4 hours.

Although Wallace's family typically cooked for only a few minutes each morning and evening, concentrations of the ultrafine particles tripled throughout the house after those culinary efforts. Some 15 minutes of frying could spew roughly 100 trillion ultrafine particles, Wallace's team reports in an upcoming Environmental Science & Technology.

Conventional filters can't trap these particles. However, Wallace found that an electrostatic precipitator that he installed in his ducts could remove about 90 percent of the ultrafines, but only if the filtering system was cleaned monthly.--J. R.