Modeling CONSEXPO

CONSEXPO, EUSES and USES each provide multiple exposure levels via all routes with various options in line with the package of the EU Technical Guidance Document (EC, 1996). Of these models, CONSEXPO and MCCEM provide a... 

Many models are available for calculating exposure, but the European Union System for the Evaluation of Substances (EUSES) is the most commonly used in the EU. Variations in human populations across Member States are considered in terms of body weight, diet, and activities [133]. Consideration is also given to susceptible individuals such as children and the elderly [133]. More specific models are used in conjunction with EUSES to assess occupational dermal exposure (DERMAL), occupational inhalation (EASE) and consumer exposure (CONSEXPO) (see [134]). 

The CONSEXPO model for predicting consumer exposure is limited by a lack of data on chemicals in products [138]. 

Source and Sink Behavior of Aerosol Droplets 217 Sink Degradation of Pesticides in Indoor Air 218 Sink Diffusion of Pesticides into Room Materials 219 MODEL VALIDATION 220 Conceptual Validation 220 Numerical Validation 221 SOFTWARE OVERVIEW 225 EUSES and USES 225 Features 225 Theoretical 226 Remarks 227 CONSEXPO 227 Features 227 Theoretical 227 Remarks 229 SCIES 229 Features 229 Theoretical 230 Remarks 230 MCCEM 231 Features 231 Theoretical 232 Remarks 232 THERdbASE 232... 

A mass-balanced air quality model, such as is used in CONSEXPO and MCCEM, is the most widely accepted indoor air quality model. This focuses only on the air in the room environment, assuming that concentration in a room is uniform. Interactions of pollutant gain and loss are most often described through a differential equation that is applied to a defined indoor volume, as follows ... 

Numerical validation for pesticide movement addresses the question of whether the results generated from the model predict actual experimental values. A few models have been validated by correlating the estimated airborne pesticides and/or the amount on room materials with actual measurements in certain specific cases, van Veen et al. (1999) reported an experiment to validate a painting model of CONSEXPO which describes concentrations of a volatile solvent in room air both during and after the application. The concentrations depended on evaporation, initial concentration of solvent in two layers of paint, volume of paint and removal of solvent by ventilation from the room. Model parameters were either measured from the room before the experiment (ventilation rate, room size, physico-chemical parameters, etc.) from the act of painting (surface painted and amount of paint used), or fixed in advanced (relative size of the two layers of paint, transfer rate between the layers, etc.). The model predicted room concentrations that were within 80 % of the actual measured concentrations (Figure 6.1). Important with respect to the evaporation term is that peak concentrations could be predicted very well, so indicating that the source term is appropriate. 

Risk notification accompanied by generic reasonable worst-case exposure with a default value of dermal absorption rate, which is a specific percentage penetration value via the dermal route. This screening tier should be quite simple, checking for the kinds of users and product use. Exposure estimates are retrieved from high-end indicative values (from databases or models) or from reasoned cases. Models suited to aid the process are EUSES/USES, SCIES/MCCEM, THERdbASE and the simple models in CONSEXPO and InPest with reasonable worst-values . 

The basic concept is that estimated results for pesticide movements and exposure levels vary greatly with the model types and modeling philosophy. Before con-dncting a model exercise, a conceptual check of the model is needed to ascertain if the model contains aU relevant routes of exposure. A simple model, such as SCIES, is based on worst-case assumptions, and may be sufficient for inhalation risk assessment. More complicated simulation models, such as CONSEXPO and InPest, provide information on the amounts of pesticides on the room materials, as well as the airborne concentration, and they are appropriate for risk assessment via aU routes. Even in complicated models, each mechanistic model contains assumptions to simplify the process description of the pesticide movement in the real world . The underlying assumptions for each of the models, and the relevant processes they implicate, are criteria to consider when selecting an appropriate model. Therefore, the validity of the assumptions used for the assessment should be considered before using the model, and they should be well documented. A simple phrase such as, we used model xx to estimate an exposure level of yy, is inadequate for documentation purposes. 

GExFRAME. A generic consumer exposure modeling system intended to harmonize source models, fate and transport models, and exposure/risk models, GExFrame is being developed to accommodate various algorithms including those that reside in CONSEXPO, E-FAST, CARES, and similar models. 

Dehnaar, J.E., Park, M.V.D.Z., and van Engelen, J.G.M. 2005. ConsExpo 4.0 Consumer Exposure and Uptake Models Program Manual. RIVM report 320104004/2005. Available at http //www.rivm.nl/dsresource objectid=rivm p 13097 type=oi disp)osition=inline ns nc=l (accessed November 29,2013). 

BEAT is only intended for predicted occupational exposure and not consumer exposure. Predictive consumer exposure can be determined using the CONSEXPO model developed by RIVM in the Netherlands and incorporated into EUSES (the European Uniform System for Evaluating Substances). In the USA residential SOPs have been developed for consumer use of antimicrobials and pesticides in the house. These models include ... 

---