Indoor chemistry and health: where are we going?

Indoor chemistry is receiving attention due to the possible health effects of products ofreactions between indoor pollutants, and the potential for such products to contribute to indoorparticulate matter (PM). Much of the focus with respect to indoor chemistry has been onterpene/ozone reaction products, since terpenes are ubiquitous indoors, ozone readilyinfiltrates from outdoors, and the reaction rates are comparable to typical air exchange rates inmany indoor settings. Several studies have documented particle formation from reactionsbetween ozone and a-pinene or d-limonene. In addition, respiratory effects in mice have beennoted with these reaction products, and those of isoprene and ozone and isoprene and nitrogendioxide. Sensory irritation and airflow limitation have been observed during exposure toterpene oxidation products (TOP), and enhanced effects were observed with repeatedexposures, suggesting a cumulative effect. These findings have important implications forindoor settings where occupants may be chronically exposed to TOP. However, althoughterpenes are important indoor pollutants, other unsaturated hydrocarbons and oxidants warrantstudy. This paper reviews the accumulating literature regarding possible health impacts fromproducts formed through indoor air chemistry, and suggests additional research directions.