Lemon-scented products spawn pollutants

While prepping for holiday guests, many hosts will deploy cleaners and air fresheners that impart a pleasant lemon or pine scent. Though they can mask stale smells, their fragrant ingredients—under certain conditions—may also be a rich source of indoor pollution, a study finds.

Several years ago, Charles J. Weschler, a chemist at Telcordia Technologies in Red Bank, N.J., stumbled onto the polluting alter ego of an aromatic citrus compound. While experimenting with the terpene called limonene, Weschler noticed a white message board in the lab turning dingy. Investigation revealed it was building up a thin coat of submicron particles that were forming in reactions between limonene gas and ozone.

Scientists have long known that much of the haze shrouding eastern U.S. forests traces to particulates created in reactions of ozone with terpenes, such as the fragrant pinene emitted by evergreens. The size of these and other small particulates—less than 2.5 micrometers in diameter—permits people to inhale them deeply into their lungs. EPA regulates outdoor particles of this size, which aggravate heart and lung disease.

Weschler teamed up with chemists at Rutgers University in Piscataway, N.J., to study the conditions under which terpene-derived particulates form indoors. The New Jersey team sprayed a wooden coffee table for 15 seconds with a lemon-scented wax and measured limonene’s release into the air for the next 3 hours. Then, they loaded a test chamber with concentrations of limonene similar to those recorded and of ozone typical of indoor air on a smoggy, summer day.

Within 30 minutes, particulates started forming. Under the most productive conditions, notes Junfeng Zhang of Rutgers, air concentrations of the particulates reached one-third of the revised particulates limit for outdoor air under proposed federal rules (SN: 12/21&28/96, p. 410). Zhang and Weschler’s team reports its findings in the December Environmental Health Perspectives.

What C. Arden Pope Jr. of Brigham Young University in Provo, Utah, finds “interesting” about the study is that the interaction of ozone and a seemingly innocuous cleaner can generate enough particulates indoors to approach concentrations that have triggered adverse health effects.

However, cautions Joel Schwartz of the Harvard School of Public Health in Boston, no one yet knows whether these terpene-derived particulates are as toxic as those that typically form in outdoor urban air.