Ozone-induced formation of aldehydes was studied on the surface and in the gas phase above carpets and on carpet components. Samples of four carpets were exposed to 100 ppb ozone. Emission rates of aldehydes and other organic compounds were measured from exposed and unexposed samples. Surface interactions of ozone with carpets produced C1-C13 n-aldehydes and several unsaturated aldehydes. Total aldehyde emission rates increased markedly with ozone exposure, from 1 to 70 microg m(-2) h(-1) for unexposed samples, to 60-800 microg m(-2) h(-1) during exposure. One exposed sample emitted large amounts of 2-nonenal (180-230 microg m(-2) h(-1)), a compound with a low odor threshold. Material balance modeling of a residence with this high emitting carpet suggests (1) that the concentration of 2-nonenal would be well above its odor threshold even in areas with only moderate ambient ozone levels and (2) that odorous levels of 2-nonenal could persist for years. Reactions of ozone with gas-phase primary emissions from carpet significantly reduced the levels of 4-phenylcyclohexene and produced small amounts of branched ketones. Separately measured patterns of aldehyde emissions from ozone exposure of linseed and tung oils were similar but not identical to those observed from ozone-exposed carpets.

To assess the influence of clothing on dermal uptake of semi-volatile organic compounds (SVOCs), we measured uptake of selected airborne phthalates for an individual wearing clean clothes or air-exposed clothes and compared these results with dermal uptake for bare-skinned individuals under otherwise identical experimental conditions. Using a breathing hood to isolate dermal from inhalation uptake, we measured urinary metabolites of diethylphthalate (DEP) and di-n-butylphthalate (DnBP) from an individual exposed to known concentrations of these compounds for 6 h in an experimental chamber. The individual wore either clean (fresh) cotton clothes or cotton clothes that had been exposed to the same chamber air concentrations for 9 days. For a 6-h exposure, the net amounts of DEP and DnBP absorbed when wearing fresh clothes were, respectively, 0.017 and 0.007 μg/kg/(μg/m(3)); for exposed clothes the results were 0.178 and 0.261 μg/kg/(μg/m(3)), respectively (values normalized by air concentration and body mass). When compared against the average results for bare-skinned participants, clean clothes were protective, whereas exposed clothes increased dermal uptake for DEP and DnBP by factors of 3.3 and 6.5, respectively. Even for non-occupational environments, wearing clothing that has adsorbed/absorbed indoor air pollutants can increase dermal uptake of SVOCs by substantial amounts relative to bare skin.

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Field experiments were conducted in four homes during summerto quantify ozone-induced secondary emission rates (SERs) of aldehydes on indoor surfaces. Four surfaces in each house were examined: living room carpet, living room wall, kitchen floor, and kitchen counter. Upon exposure to ozone for 3 h, formaldehyde and C3-C10 saturated aldehydes, especially nonanal, were emitted as products of ozone-surface reactions. Carpet in newer homes had higher SERs than carpet in older homes. For example, the nonanal SER from the living room carpet was 80 microg m(-2) h(-1) in a 1 year old home, but only 8-20 microg m(-2) h(-1) in two homes that were greater than 10 years old. All kitchen countertops were very reactive and high SERs were observed, especially for nonanal. Product yields from countertops were consistent with the products of ozone reactions with oleic and linoleic esters, common in cooking oils. These findings suggest that carpet surfaces become depleted of reactants as they become oxidized over time. However, countertop surfaces, which are cleaned frequently or become covered in cooking oils, are continuously replenished with reactants. Over time, countertops may become the dominant contributor to indoor concentrations of secondary aldehydes. However, when total surface area is taken into account for the homes assessed, carpet is predicted to be the primary source of secondary emissions, even for older homes.

Multiphase reactions of ozone with human skin oils impact indoor air quality by depleting ozone and forming semi-volatile organic compounds, which can be respiratory and skin irritants. Here we demonstrate the impact of clothing on indoor air composition and human exposure by integrating indoor chemistry modeling over a wide range of different spatial and temporal scales. Constrained by molecular dynamics simulations that provide key kinetic parameters, the kinetic model reproduces experimental measurements and predicts that squalene could persist in clothing for several hours to over a day depending on ozone concentrations. Soiled clothing protects skin from ozone exposure even with high concentrations, but can enhance concentrations of oxidation products to a ppb level depending on air exchange rates. Computational fluid dynamics simulations reveal that primary products have~1.6-2.0 times higher concentrations in the breathing zone than in bulk room air, while secondary products are distributed more uniformly throughout a room.