Exposure multimedia

Wallace LA, Pellizzari ED, Sheldon L, et al. 1986d. The total exposure assessment methodology (TEAM) study Direct measurement of personal exposures through air and water for 600 residents of several U.S. cities. In Cohen Y, ed. Pollutants in a multimedia environment. New York, NY Plenum Publishing Corp., 289-315. 

Another case of multimedia fate modeling may be exemplified by human inhalation exposure estimates for PCB spills. The spill size is estimated considering both spread and soil infiltration. Volatilization calculations were carried out to get transfer rates into the air compartment. Finally, plume calculations using local meteorological statistics produced ambient concentration patterns which can be subsequently folded together with population distributions to obtain exposures. 

Model Types. If it is determined that exposure pathways of interest intersect more than one of the media, the analyst is faced with the need to link together single media models (or to apply existing multimedia models). Despite claims to the contrary, there is probably no single model that is appropriate to all problems. Thus, a hybrid combination of boundary... 

Multimedia model for fate and exposure analyses of chemicals Ecotoxicological effects Not considered... 

The current version of CalTOX (CalTOX4) is an eight-compartment regional and dynamic multimedia fugacity model. CalTOX comprises a multimedia transport and transformation model, multi-pathway exposure scenario models, and add-ins to quantify and evaluate variability and uncertainty. To conduct the sensitivity and uncertainty analyses, all input parameter values are given as distributions, described in terms of mean values and a coefficient of variation, instead of point estimates or plausible upper values. 

Fate and exposure analyses. The multimedia transport and transformation model is a dynamic model that can be used to assess time-varying concentrations of contaminants that are placed in soil layers at a time-zero concentration or contaminants released continuously to air, soil, or water. This model is used for determining the distribution of a chemical in the environmental compartments. An overview of the partitioning among the liquid, solid and/or gas phases of individual compartments is presented in Fig. 7. The exposure model encompasses... 

Multimedia model for fate analysis and extensive analysis of exposure pathways Human toxicity... 

FUN tool is a new integrated software based on a multimedia model, physiologically based pharmacokinetic (PBPK) models and associated databases. The tool is a dynamic integrated model and is capable of assessing the human exposure to chemical substances via multiple exposure pathways and the potential health risks (Fig. 9) [70]. 2-FUN tool has been developed in the framework of the European project called 2-FUN (Full-chain and UNcertainty Approaches for Assessing Health Risks in FUture ENvironmental Scenarios www.2-fun.org). 

McKone TE, Layton DW (1986) Screening the potential risks of toxic substances using a multimedia compartment model estimation of human exposure. Regul Toxicol Pharm 6 359-380... 

McKone TE (1993) CalTOX, a multimedia total exposure model for hazardous-waste sites. Part I. Executive summary. A report written for The Office of Scientific Affairs Department of Toxic Substances Control California Environmental Protection Agency Sacramento, California by the Lawrence Livermore National Laboratory, Livermore... 

Gobas FAPC, Pasternak JP, Lien K, Duncan RK (1998) Development and field validation of a multimedia exposure assessment model for waste load allocation in aquatic ecosystems application to 2,3,7,8-tetrachlo-rodibenzo-p-dioxin and 2,3,7,8-tetrachlorodibenzofuran in the Fraser river watershed. Environ Sci Technol 32(16) 2442-2449... 

Environmental exposure (direct). Exposure through air inhalation, soil and dust ingestion, and dermal contact of soil and dust are the principal exposure pathways. Other exposure pathways (e.g., water dermal contact) can be taken into account in some scenarios. Monitoring campaigns or multimedia fate models are used to assess the exposure (see [4]). 

Food and water ingestion (dietary exposition). To assess the dietary exposure, ingestion rates of the different food products and water are needed. Multimedia fate models or food sampling campaigns are the main ways to determine the concentration of substances in food products and water at the specific scenario. These models consider cattle, meat, milk, fish, crops, and drinking water, among others. 

There are many models for assessing risks to human health and/or the environment. Some of them are multimedia models, which assess the exposure and risks in different environmental matrices, such as soil, air, water, and food chains with different degrees of complexity within each medium. Conversely, others are more specific with regard to a medium or a system (e.g., river or food chain). Other models assess only human health risks or environmental risks, while some assess both risks. Based on the type of scenario that is studied, an appropriate model will be chosen. 

However, as a general observation, this study demonstrated the feasibility of the integrated modeling approach to couple an environmental multimedia and a PBPK models, considering multi-exposure pathways, and thus the potential applicability of the 2-FUN tool for health risk assessment. The global sensitivity analysis effectively discovered which input parameters and exposure pathways were the key drivers of Pb concentrations in the arterial blood of adults and children. This information allows us to focus on predominant input parameters and exposure pathways, and then to improve more efficiently the performance of the modeling tool for the risk assessment. 

Richardson, M., M. Mitchell, S. Coad, and R. Raphael. 1995. Exposure to mercury in Canada a multimedia... 

Derive Input Data for Multimedia Models and Wastewater Treatment Plants (WWT) Models (9/1/2000) http //www.epa.gov/ oppt/exposure/pubs/halflife.htm (last accessed 27 September 2011). 

Some children are exposed to toxic chemicals or to hazardous environments in unique circumstances. There is a need to understand chemical exposures and other health stressors in special settings in the world (child labourers, street children, refugees). Globally, millions of children live under these conditions. Currently, data on children s exposures are inadequate to effectively assess multimedia and multiroute exposures in order to conduct child-protective risk assessments. The limited exposure data that are available have focused on children in developed countries, and information on the levels of chemical exposures in children in developing countries is generally lacking. 

In environmental exposure assessments, level II and III multimedia models require compart-mental half-lives (t1/2) for air, water, soil, and sediment. The most relevant compartments vary with the chemical being evaluated, but experimental data for every compartment are generally not available. To evaluate the environmental residence time of compounds adequately, the various degradation pathways have to be considered in combination. The extent, rates, and byproducts of the individual processes should preferably be integrated. The degradation reactions may take a... 

Figure A2.1 Multimedia, multipathway, multiroute exposure assessment...

In this case-study, the issue of concern is the extensive exposure of human populations to PBLx, which is a persistent pollutant with multimedia and multipathway exposure potential. For PBLx, exposures occur primarily through food pathways. Here we focus on fish ingestion exposures from PBLx emissions to air that are deposited on ocean and fresh waters and accumulated in both ocean and freshwater fish. This situation focuses attention on three key pieces of information—concentration in water, biotransfer to fish and human consumption of fish. 

So far, the main focus of multimedia fate models has been on single chemicals, but extensions may become available to include fate of transformation products. This may open the way to making the models applicable to mixtures (OECD 2004). Initially such development may simply be made through the serial analysis of the fate of individual chemicals, and from this a derivation of probable concentrations of each, assuming no interaction. Such analysis is, for example, feasible for many of the most widely used down the drain and is at present being extended to other product types, such as personal care chemicals and human pharmaceuticals. Such combined analysis would in fact represent a considerable step forward in addressing the nature of likely mixture exposures however, if the interactions with the environment and between chemicals as outlined above are to be considered, then this would require a considerable effort to understand and include the major processes involved within existing models. 

Research on potential interactions between individual chemicals that might affect the exposure, availability, or toxicity of the mixture and inclusion of outcomes into developing multimedia fate models for mixtures. 

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