Modeling MCCEM

The Multi-Chamber Concentration and Exposure Model (MCCEM), Version 2.4, was developed by GEOMET Technologies, Inc., for the USEPA Office of Pollution Prevention and Toxics. It has been designed to estimate indoor concentrations for chemicals released in residences (GEOMET, 1995). It has the... 

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 ... 

The SCIES and MCCEM models give only inhalation exposure, but the simulated results can be incorporated into a whole-risk assessment in the residential space such as the USEPA SOP framework (USEPA, 1997b) which estimates multiple exposure levels via all routes (i.e. inhalation, dermal and oral). THERdbASE is capable of estimating inhalation and dermal exposures based on the simulated airborne concentration and the film-thickness theory, and InPest estimates all exposures, including oral routes, based on the simulated concentration in the air and amounts on the room materials (Matoba et al., 1998c). 

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... 

Figure 6.4 Comparison between measured and estimated values for a pyrethroid pesticide in the air. A space aerosol product containing 0.45 g of rf-tetramethrin was uniformly sprayed for a total of 10s in a room (/, 3.6m w, 2.7m h, 2.4m) at an air-exchange rate of 1.55h . The concentrations of rf-tetramethrin in the air after spraying were measured (symbols) (Matoba et al., 1998a) and compared with those simulated by the MCCEM (-------) and InPest models (---------)...

MCCEM requires time-varying emission rates for a chemical in each zone of the residence and outdoor concentrations. The emission rates of pollutants can be entered into the model either as numbers or as formulae. 

MCCEM has data sets containing infiltration and interzonal airflow rates for different types of residences in various geographic areas. The user can select from the data sets or can input zone descriptions, volumes and airflow rates. Concentrations can be modeled in as many as four zones (chambers) of... 

Models 103 and 104 generate release parameters of chemicals, such as the evaporation time estimated by the Chinn evaporation method, to run Model 105. These are characterized by two zones (as with the SCIES model) or Model 106, characterized by n zones, where n is up to four (such as for the MCCEM model). 

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 . 

USEPA, MCCEM. Multi-Chamber Concentration and Exposure Model, User s Guide, Version 2.3, Office of Research and Development, Environmental Monitoring Systems... 

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