David Olson

Indoor fine particles: The role of terpene emissions from consumer products

Abstract Consumer products can emit significant quantities of terpenes, which can react with ozone (O3). Resulting byproducts include compounds with low vapor pressures that contribute to the growth of secondary organic aerosols (SOAs). The focus of this study was to evaluate the potential for SOA growth, in the presence of O3, following the use of a lime-scented liquid air freshener, a pine-scented solid air freshener, a lemon-scented general-purpose cleaner, a wood floor cleaner, and a perfume. Two chamber experiments were performed for each of these five terpene-containing agents, one at an elevated O3 concentration and the other at a lower O3 concentration. Particle number and mass concentrations increased and O3 concentrations decreased during each experiment. Experiments with terpene-based air fresheners produced the highest increases in particle number and mass concentrations. The results of this study clearly demonstrate that homogeneous reactions between O3 and terpenes from various consumer products can lead to increases in fine particle mass concentrations when these products are used indoors. Particle increases can occur during periods of elevated outdoor O3 concentrations or indoor O3 generation, coupled with elevated terpene releases. Human exposure to fine particles can be reduced by minimizing indoor terpene concentrations or O3 concentrations.

Characterizing exposure to chemicals from soil vapor intrusion using a two-compartment model

Abstract Though several different models have been developed for sub-surface migration, little attention has been given to the effect of subsurface transport on the indoor environment. Existing methods generally assume that a house is one well-mixed compartment. A two-compartment model was developed to better characterize this exposure pathway; the model treats the house as two well-mixed compartments, one for the basement and one for the remainder of the house. A field study was completed to quantify parameters associated with the two-compartment model, such as soil gas intrusion rates and basement to ground floor air exchange rates. Two residential test houses in Paulsboro, New Jersey were selected for this study. All experiments were completed using sulfur hexafluoride (SF 6 ) as a tracer gas. Soil gas intrusion rates were found to be highly dependent on the soil gas to basement pressure difference, varying from 0.001xa0m 3 xa0m −2 xa0h −1 for a pressure drop of –0.2xa0Pa to 0.011xa0m 3 xa0m −2 xa0h −1 for a pressure drop of –6.0xa0Pa. Basement ventilation rates ranged from 0.17 to 0.75 air changes per hour (ACH) for basement to ambient pressure differences ranging from –1.1 to –7.6xa0Pa (relative to ambient). Application of experimental results in conjunction with the two-compartment model indicate that exposures are highly dependent on gas intrusion rates, basement ventilation rate, and fraction of time spent in the basement. These results can also be significantly different when compared with the simple well-mixed house assumption.

In-home formation and emissions of trihalomethanes: The role of residential dishwashers

This study involved an assessment of chloroform formation due to the use of hypochlorite-containing detergents in dishwashers. The objective of this research was to quantify in-home formation of trihalomethanes, particularly as related to dishwasher usage. A series of 14 flask and 15 laboratory experiments were completed. Flask experiments involved the mixing of food with dishwasher detergent in water for a 12-min reaction period, and were intended to identify chemicals and relative levels of those chemicals that may form from dishwasher usage with different food groups. Liquid concentrations of chloroform ranged from 1 to 41u2009mg/l. Laboratory experiments involved collection of liquid and gas samples over the course of an operating cycle with an actual residential dishwasher. Background concentrations of chloroform in the water supply were generally between 0 and 10u2009μg/l; liquid chloroform levels in the wash cycle were typically at least 50u2009μg/l. Chloroform concentrations were as high as 20u2009μg/l in the dishwasher headspace. Using mass balance equations for a typical residential house and laboratory results from this research, predicted concentrations resulting from dishwasher usage were similar to typical background concentrations in residential dwellings.

Fate and Transport of Contaminants in Indoor Air

Significant media and regulatory attention has been given to hazardous waste sites and to the remediation of such sites to protect nearby building occupants. Soil vapor intrusion (SVI) can be a major factor contributing to increased occupant expo sure to chemicals. However, there are many possible sources of indoor air pollution, thus complicating routine assessments. The intent of this paper is to provide an overview of the state of understanding related to chemical fate in the indoor environment. A generalized model is presented in the form of an ordinary differential equation that includes several terms that are not commonly accounted for in models involving the effects of SVI in indoor air. In addition to soil vapor intrusion several other sources of indoor contamination are described. Typical air exchange rates for residential dwellings are presented. Finally, recent findings related to the sorptive interactions between indoor air pollutants and indoor materials, as well as homogeneous and heterogeneous chemical reactions that can affect indoor air pollutants are described.

A new approach for estimating volatile organic compound emissions from sewers : methodology and associated errors

Previous studies have indicated the potential for emissions of volatile organic compounds (VOCs) from industrial and municipal sewers. However, existing estimation methods can significantly overestimate emissions of VOCs over a wide range of sewer operating conditions. This paper reviews three methods for estimating emissions from sewer reaches: equilibrium, open trench, and cocurrent ventilation. A new methodology is presented that combines both equilibrium and open-trench approaches. The maximum error associated with this combined model is shown mathematically to be 58% and independent of flow and reach characteristics.