The DustEx model is used to assess exposure to  semi-volatile substances (SVOCs) in products that are introduced into the indoor environment. The typical products considered are solid material products (e.g. flooring, wall covering, electronic devices) from which substances are released into indoor air and subsequently transported into different indoor compartments airborne particles, indoor surfaces and dust.

Exposure takes place from the inhalation of the substance in the gas phase, the inhalation of substance bound to airborne particles, the dermal absorption of the substance from air (gas phase) and the oral ingestion of the substance with dust. For SVOCs released indoors it may not be clear beforehand which exposure pathway(s) will be relevant. The DustEx model considers all pathways and will therefore enable a more complete assessment of exposure, reducing the probability of overlooking the most crucial pathways in the exposure assessment. In developing the DustEx model, a number of simplifying assumptions were made. These put limits on the applicability of the model in exposure assessments.

Model framework

The DustEx model is a kinetic source to dose model that contains dynamic mass balance equations describing emission and fate of the substance indoors. The integration of the system of equations using suitable boundary and initial conditions (i.e. reflecting the specific exposure scenario), gives the concentrations of a substance in all different compartments (air, product, dust, airborne particles, indoor surfaces) as a function of time. Estimates of the concentration in the different indoor compartments are combined with equations estimating exposure from contact with these media.

A graphical representation of the components and physical processes considered in the kinetic source to dose model.

The substance is emitted from the product into bulk indoor air by evaporation. From air, the substance will partition to airborne particulate matter, dust and will sorb to indoor surfaces. Removal of the substance from the indoor environment takes place via ventilation and vacuum cleaning. Exposure of a person present in the indoor environment stems from the inhalation of the substance in gas phase and bound to particles, the dermal absorption of the substance from air (gas phase), and the ingestion of the substance with dust.

More detailed information can be found in the subsections “Equations describing emission and transfer of a substance indoors”, “Models for exposure evaluation” and “Working with the DustEx web application”.

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