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.