This manual describes the use of the transfer model to estimate the transfer of dioxins (polychlorinated dibenzo-p-dioxins and dibenzofurans, PCDD/Fs) and dioxin-like PCBs (DL-PCBs) expressed in toxic equivalents (TEQ) from grass and soil to meat fat of free-ranging cattle grazing in floodplains.
In this context, ‘free-ranging cattle grazing in floodplains’ is defined as specific cattle breeds introduced by man to preserve landscape/nature areas by grazing in these areas year-round and generation on generation. These animals are not fed with commercial feed. This distinguishes them from regular cattle in the Netherlands, or cattle that grazes in the areas only during specific seasons. This model is only applicable to free-ranging cattle grazing in floodplains.
The transfer model described here is developed to estimate the transfer of dioxins in free-ranging cattle grazing on floodplains in the Netherlands, using characteristics of the “Rode Geus” as a representative breed. The model is only applicable for the types of cattle that graze an area year-round and generation on generation, are not fed with commercial feed, and that are physiologically similar to the “Rode Geus”. To estimate the transfer of dioxins, either contamination levels of individual congeners or TEQ levels can be used. The model has several input fields (left side) and output fields (right side). The input and results can be saved using the button “Report (*.docx)”. Source information and a citation suggestion are provided (top).
Step1: Animal details
To estimate the TEQ concentration in meat fat, the user has to select whether a cow or bull is considered. Furthermore, the date of birth can be specified.
Step 2: Exposure period
The user has to enter the duration of the exposure of the animals to the contaminated grass/soil and the time elapsed after exposure has ended, if applicable (both expressed in days).
Step 3: Contamination details
The user needs to provide the contamination levels and must choose whether to provide total TEQ levels or individual dioxins and dioxin-like PCBs levels (congener-specific).
If the user selects the total-TEQ option, five input fields show up that are used to describe the contamination scenario. Total TEQ concentrations in grass (ng/kg; 88% dry matter) in summer and winter should be provided. Note that winter concentrations should be equal to or higher than summer concentrations. The total TEQ concentration in soil (ng/kg; 100% dry matter) should also be provided. The user can also provide total TEQ concentrations in the milk drunk by calves in the first 6 months of their lives. This is especially important when estimating concentrations in young animals (e.g. < 1 year). Finally, the user can provide a background total TEQ concentration in feed. After contamination through grass and soil stops, i.e., the exposure period has ended, this background value is used to account for any total TEQ intake after the exposure period. The exposure period can be ended e.g. by moving cattle to a less contaminated area or by feeding them “clean” feed.
If the user selected the congener-specific option at the top of the panel, an Excel template should be downloaded by clicking on the link. This excel table contains the same five input fields described above, but for all dioxin and dioxin-like PCB congeners. If a value is not provided (i.e., the text “<provide input here>” is left in the field), a value of 0 ng/kg is assumed. Once the excel table is filled in, the user can upload it. After uploading the Excel file, a table will be shown which the user can use to check the input values that are used.
Step 4: Regulatory limit (optional)
Regulatory limits (for instance maximum levels) (expressed in pg total TEQ/g meat fat) can be provided. These limits will be plotted in the output graph as a red line.
Step 5: Running model
The “Run model” button, present at the bottom of the input fields can be used to run the model. After changing a value in any of the input fields, the “Run model” button has to be used again to update the results.
Step 6: Results
After running the model the results will appear in the output field on the right. If the user selected `Total TEQ` in step 3, only the simulated Total TEQ in meat fat can be selected. If `Congener-specific` was selected, the user can select to visualize the dioxin TEQ, dl-PCB TEQ, the sum TEQ (i.e., weighted sum of individual congeners), or the Total TEQ. The graph displays the selected TEQ concentration in meat fat (pg/g fat) over time, with the x-axis denoting the dates. In addition, if provided by the user, the red line denotes the regulatory limit value.
Several tools for viewing the graphs become visible on the right top of the graphs when hoovering anywhere in the graphs. When hovering over the simulated TEQ concentration, the exact Date and concentration are shown. In addition, options to save and zoom are also available.
Besides the graph visualizing the simulation results, the user can also view the data table of the underlying data. This can been displayed when selecting the Table tab on the top of the tool. This will show all relevant simulated data in a comprehensive table.
Note: Cows start lactating between April 1st and October 1st, after they have reached an age of 2 years. When simulating TEQ concentrations in a cow, this may lead to a lower TEQ concentration in meat fat in the third simulated year compared to the year before.
Step 7: Saving input and output
Using the “Report (*.docx)” button, present at the bottom of the input fields, input data and the results of the model run can be stored locally as a report file in word. Input data and results are not stored at the website.
The comprehensive table can also be exported in various file formats (.csv, .xlsx, .pdf) by pressing the button with the desired file format on top of the table.
Step 8: Citation suggestion
At the top of the model page the references that describe the model are listed, as well as a citation suggestion. Please use the suggested citation when referring to the model.