Work Package 1: Project coordination
The project will be managed through a scientific committee (project applicants and all project members; head: S. Lerch). The scientific committee will regularly schedule online meetings to discuss findings, examine progress and milestones, find alternative plans in case of difficulties, and share strategic decisions for the next steps. WP 1 will organise kick-off, mid, and final plenary meetings. All publications or end-user guidelines arising from the In SiliCont project will be published in open-access mode and include the statement that the results were generated with the assistance of BLV, and putatively other offices, financial support.
Work Package 2: Optimize and evaluate the predictive capabilities of the growing lamb PBTK model for PCBs and PCDD/Fs
Four PBTK models have been developed so far at Agroscope. These models were specifically optimized in order to describe the fate of POPs into i) lactating cows (dairy or beef, RuMoPOP and AgroPOP projects), ii) growing cattle (MeatPOP and BoviSafe projects), iii) suckler ewes and iv) growing lambs (ProxyPOP project). To date, only the first two bovine models have been optimized for PCBs and PCDD/Fs and their predictive capacity assessed against external datasets. For the ovine models in the ProxyPOP project, only the ewe model has been specifically optimized for PCDD/Fs (i.e. tissue distribution and hepatic metabolism parameters) using the in vivo dataset from the experiment conducted in Lausanne in 2022. Up to now, without having such toxicokinetic data in lambs, these parameters were transposed from the ewe to the lamb model without modification. In order to confirm the reliability of the lamb model, an evaluation of its predictive capabilities should be carried out using an independent dataset. For such task, the data from a former study on PCDD/F toxicokinetic in lamb will be used (Hoogenboom et al., 2015).
The aim of WP 2 is to i) quantitatively assess the predictive capabilities of the lamb model for PCDD/Fs, by comparing model simulations to biological observations from the toxicokinetic experiment on growing lambs previously conducted at the BfR (Hoogenboom et al., 2015), and ii) extend the calibration for the PCBs that were also measured in the latter study. This experimental dataset will be made available by the BfR as partner of the In SiliCont project.
Work Package 3: Implement the models into the ConTrans web platform, including documentation for end-users.
Once the predictive capabilities of the PBTK models for PCDD/Fs and PCBs have been evaluated and found to be satisfactory (i.e., deliverable from WP 1), the aim of WP 3 will be to make them available online via the BfR's ConTrans web platform.
The first step is to define the desirable levels of detail and flexibility for user’s parameterization of the simulation set-up. A decision will have to be made regarding the user interface such that the optimal trade-off between flexibility and generality is found. This should enable specific cases to be described, while limiting the complexity and number of parameters supplied by the user at the time of the simulation set-up. This will be defined after gathering the needs of the main users (e.g. BLV, BLW, BAFU, cantons and possibly industrial stakeholders), as well as the logistic and computing capacities of the ConTrans platform.
In a second step, the primary versions of the four models will be converted into simplified versions in which all the parameters and variables will be clearly and explicitly presented. This will be carried out by Agroscope using the dynamic modelling software Vensim®, in coordination with BfR, in view of formal requirements to carry out the final step.
The final step consists in converting the simplified and explicit versions of the four models delivered by Agroscope, into new modules (i.e., interactive web pages) of the ConTrans web platform.
Work Package 4: Assess the risk of on-farm contamination of cow and sheep milk and meat by PCBs and PCDD/Fs from feed and soil in extensive grass-based production systems.
The WP 4 will make use of the four PBTK models (deliverables of WP 2 and 3) in order to deliver practical guidelines for the safe management of dairy, beef and sheep production systems. A specific focus will be made on extensive grass-based feeding systems, where the risk of livestock exposure through ingestion of soil particles loaded with POPs is heightened (Weber et al., 2018). In such circumstances of diffusive source of contamination, a model-based risk assessment would be of immense help in order to define thresholds in feed and soil POP levels in order not to exceed the maximum levels (MLs) and to prevent at-risk farming practices and ensure the production of safe milk and meat from extensive husbandry.
A series of husbandry scenarios, defined by farming practices (species, breeds, productive levels, feed regimens…) and levels of POP exposure (intake and contamination levels of feeds and soil) will be simulated using the four PBTK models, and the achieved milk and meat (adipose tissue and muscle) PCBs and PCDD/Fs concentrations recorded and compared to the MLs. This will made use of the deliverables of the former MeatPOP project[1], for defining the feeding systems of suckler beef herds, and extend to the cases of dairy cow herds and suckler sheep herds, and for establishing realistic distributions in the PCBs and PCDD/Fs concentrations into each of the feedstuffs, as well as in agricultural soils that will be included to the typical diets at a rate of 1% to 9% of the total dry matter intake (Jurjanz et al., 2012; Morel et al., 2022).
[1] Co-funded by the Bafu and Mutterkuh Schweiz.
