Exposure Routes and Types of Exposure

Abstract

Exposure to indoor air contaminants occurs not just through inhalation but also via dermal absorption of vapors or when touching surfaces that air contaminants deposit on, and by inadvertent ingestion of contaminated settled dust from hand to mouth behaviors, especially for children. Sources of indoor pollutants include penetration of outdoor air, emissions from indoor use of consumer and personal products, furnishing and building materials, resuspension of house dust, and indoor air chemistry. Multiple sources, limited ventilation, and finite volume of buildings results in higher air concentrations of many volatile and semi-volatile organic compounds within homes than outdoors. When personal products are used near the breathing zone, the concentration of the air breathed, and therefore the resulting inhalation exposure, can be higher than estimated from the indoor air concentrations. Semi-volatile organic compounds (SVOCs) partition between indoor air and surfaces, particularly into house dust which serves as a reservoir for many compounds. The partitioning of SVOCs between indoor air and surface/ dust results in their having multiple exposure routes. This chapter presents examples of exposures that occur to various chemicals representative of broad categories of compounds, thereby providing general concepts that should be considered when evaluating potential exposures to indoor air pollutants. Since people spend, on average, more than 90% of their time indoors, indoor air is often the largest contributor to total exposures for volatile, semi-volatile, and particulate air contaminants.