Supporting data for Non-extractable residues (NER) in persistence assessment - effect on the degradation half-life of chemicals

Data has been collected from already published studies on chemical degradation in OECD 307, 308 or 309 tests or similar tests. All collected data is presented in the Excel-file "Data from degradation studies". In some studies the data was only presented in graphs. Here, the tool PlotDigitizer was used to extract the data from the graphs.

Included studies has extractable parent substance, CO2, and NER measured at at least 5 timepoints.

For all substances we had data for, a reaction equation was set up using a set of rules determined for use for the Microbial Turnover to Biomass (MTB) method. The reaction assumed for each substance can be found in the Word-file "Reactions".

With the reaction, we could move on to predict the amount of bioNER developed during each study, using the MTB method. The calculations for each substance is seen in the Excel file "MTB sheet"

Combining the data from the studies and the results from the MTB calculations, we investigated how different approached towards NER affected the degradation curve. The 4 investigated scenarios are set up for each substance in the Excel-file "Scenarios for input to CAKE".

For the following substances, a relevant metabolite has been modelled as well: glyphosate, thiamethoxam, triclosan.

The unit is %aL (% applied label) which is the percentage of the initially added compound. The tested compound is labelled, in order to follow its fate throughout the study.

3 scenarios were assessed for each laboratory test where the included amount of NER vary:

i) Parent only: only measured extractable parent compound (except for the starting value at time 0, where any formed metabolite or NER is added to the extractable parent too).

ii) Parent + tNER: extracted parent compound + total amount of NER measured.

iii) Parent + (tNER - MTBbioNER): Same as ii) Parent + tNER, except that the amount of bioNER calculated with the MTB method has been subtracted.

In cases where measurements of NER I has been performed, an extra scenario is included, as NER I is considered to be the potentially hazardous part of NER:

iv) Parent + NER I: Measured amount of extractable parent compound + measured amount of NER I, determined with either silylation or EDTA extraction.

We investigated the degradation kinetics for 24 substances in the program CAKE (Computer Assisted Kinetic Evaluation). CAKE is available for download at https://cake-kinetics.org/, all CAKE-files from the study are in the folder CAKE-files.

Each substance has its own CAKE file, which contains data from one or more laboratory studies on that substance.

Where more studies have been performed with the same substance, all tests are included in the CAKE file, distinguished by eg. an abbreviation of their difference (eg. if two tests were made, and the OECD tests differ between the two (so OECD 308 and 309 has been made), one dataset will have 308 on all sheet names related to the OECD 308 test and the sheets related to the OECD 309 test, will have 309 in the name.

As a backup of our results, we copied the outputs from CAKE to Word-files, in case someone without access to CAKE would like to investigate our results. We divided the outputs into two different files, depending on the chosen degradation kinetic, either SFO (used in the article) or DFOP.

These are found in the Word-files "SFO outputs from CAKE" and "DFOP outputs from CAKE"