3.0 Model Framework
3.1 Objectives
3.2 Approach
3.3 Requirements
3.4 Design
3.5 Data Exchange Protocol
3.2 CCEF Approach
The American Chemistry Council's Human Health Exposure Assessment Technical Implementation Panel identified four example exposure scenarios associated with different high-volume compounds that the design of the CCEF should address. Using the design of the CCEF and its applicability to the four example exposure scenarios, research gaps and needs were identified. The filling of these research gaps and needs would increase the confidence and reduce the uncertainty of the human health exposure assessment results.The four example exposure scenarios were used to guide the types of models, algorithms, and databases required to evaluate each scenario. Model and Process Flow Diagrams were developed for each exposure scenario and research gaps were identified based on publicly available information. Once the gap analysis was completed for the source, transport, exposure, and health impact components of each scenario, a qualitative sensitivity of the entire system was conducted.
The Gap Analysis focused on reviewing the Process Flow Diagrams that had been developed to properly evaluate each of the four example exposure scenarios to identify models, algorithms, and databases that were missing or unknown. This was done for the Source, Transport, Exposure, and Impacts components of the exposure scenarios. In some cases, models existed but they were determined to be too simplistic or conservative and were considered a research gap. In these cases, alternative paths were explored to determine the type of model or algorithm required to fill the research gap.
A qualitative Sensitivity Analysis was also performed on the models and algorithms identified for the various compounds and exposure scenarios. This was conducted on the four modeling components using the following guidelines:
- Models associated with the primary exposure pathway were believed to introduce more sensitivity than those on secondary exposure pathways
- Missing models and databases were considered a high priority
- Inaccurate models were ranked as a high priority
- Models of lesser compatibility in temporal and spatial scales with the other models were considered a high priority
The Gap and Sensitivity Analyses provide guidance on what research should be conducted in the near future to improve the risk estimates from exposure to high volume compounds.
The design of the CCEF leverages the concepts associated with multiple existing framework system software and exposure modeling methods that are in the forefront of the scientific community as well as new innovative concepts. The key to the CCEF will be the flexibility of the CCEF in its usability and ability to integrate and accommodate different exposure models (existing and future) required for the American Chemistry Council and industry needs.
The CCEF design links models and databases together so they can transparently communicate between each other. The CCEF is the overarching framework that houses the models and databases as "separate" components and provides the data file protocols for communication between components. A model is represented by a specific set of algorithms that perform a specific function (e.g., drinking water ingestion model). A module represents a general set of model types, defined by their "real world" functions, and includes the model, its user interface, and any pre- and post-processors that facilitate linkages and communication with/to other components (e.g., models and databases). This effort focuses on the design of an overarching framework and not on the models that are housed within the framework.
