Model Development

Mathematical modelling is a key component of risk assessments and allows notifiers and regulators to calculate Predicted Environmental Concentrations (PECs). Understanding the environment and being able to use this knowledge to correctly parameterise models is paramount to producing accurate risk assessments. At CEA we are able to utilise our extensive skills and knowledge of landscapes to build models that better simulate reality.

Our programmers work closely with our technical experts in chemistry, environmental fate, ecotoxicology and landscape analysis to develop models to serve the chemical industry and regulatory bodies. Examples of recent models are given below:

Phase I Calculator
The calculation of PEC values in soil is an essential part of the environmental risk assessment process for veterinary medicines used for livestock. Under CVMP/VICH an unrefined PEC in soil should be calculated at Phase I to indicate whether further consideration of environmental risk is necessary. CEA have developed a software tool that enables notifiers to quickly calculate PEC values for a range of different treatment types using standard calculation methodologies and parameters. The software recalculates PEC values 'on-the-fly' so that the effect of critical parameters can be investigated. Output from the software includes a word file that details the appropriate equations and parameters which can be incorporated directly into risk assessment reports.

VetCalc
The VetCalc model was developed by Cambridge Environmental Assessments (CEA) using funding from The Veterinary Medicines Directorate and Defra in the UK to assist in the preparation of environmental risk assessments for veterinary medicines at Phase II under Directive 81/852/EEC (as amended by Directive 04/28/EEC).  The model provides a simple software tool to for estimating environmental exposure associated with the use of livestock treatments, taking into account key drivers such as treatment regimes (both bodyweight and non-body-weight related), animal characteristics and husbandry practices, manure characteristics and management regimes, environmental characteristics (soil, hydrology, weather), agricultural practices and chemical properties. VetCalc may be used to estimate PEC values for soil, groundwater and surface water for 12 predefined scenarios which were chosen on the basis of livestock production and diversity, agricultural practice and climatic zone. The VetCalc model is freely available and can be downloaded here.

Aquaculture
The standard approaches to evaluating the environmental impact of chemical use in marine aquaculture provide site-specific assessments that allow iterative calculation of maximum permissible treatment rates. However, environmental assessments of aquaculture medicines at Phase II under Directive 81/852/EEC (as amended by Directive 04/28/EEC) require a non site-specific prediction of exposure resulting from a pre-determined treatment rate. To achieve this, the principles and assumptions that are used to describe chemical dispersal in the short-term bath treatment model developed by SEPA (2002) were adapted to fit into a deterministic modelling framework. One of the key advantages of the modelling framework developed by CEA is that it enables prediction of exposure associated with repeated releases of chemical that are associated with courses of treatment.