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TSCF & PUF - New study type to offer greater accuracy in environmental fate assessment for plant protection products

19th November 2020

Blog by Dr. Victor Gourlay, Study Director at ibacon: "Transpiration Stream Concentration Factor (TSCF) and Plant Uptake Factor (PUF) - New study type to offer greater accuracy in environmental fate assessment for plant protection products" 

At ibacon, we are preparing to offer a new study type to improve and refine the risk assessment of plant protection products. Transpiration Stream Concentration Factor (TSCF) and Plant Uptake Factor (PUF) are used to quantify the amount of product taken up in crop plants via roots within the transpiration stream.

ibacon already has a broad experience in determining the effects of plant protection products on Non-Target Terrestrial Plants (NTTP). Our state-of-the-art growth rooms are designed to deliver the very best conditions for plant growth, and they feature LED lamps that offer ultimate light quality alongside optimal air humidity and temperature.

Historically in risk assessment, the amount of a product taken up by plants was set at a default value of 0.5 (the concentration in plants being half of that in pore water). In the absence of experimental data, authorities currently require to use a value of 0 (no uptake). As this may underestimate the amount taken by the plant, a study design is under development to determine the uptake using the TSCF. If experimental data confirm the uptake, the experimental value can then be used, with a conservative maximum of factor 0.5.

For this study type, plants are grown from seeds to the BBCH 13 stadium (three true leaf stage) in hydroponic conditions. At that stage, the test chemical (14C-labelled) is spiked into the hydroponics system, the plants are transferred to this treated hydroponics system, and the TSCF is determined over a period of 6-8 days.

Calculated values of TSCF are generally between 0 and 1. If the chemical is not passively taken up by the plant, the factor is 0. If the chemical is taken up unhindered within the transpiration stream, the factor is 1, meaning the same concentration in pore water and in xylem.

The basis for the current development is the study “Evaluation of a novel test design to determine uptake of chemicals by plant roots” (Lamshoeft et al), published in 2018 in Science of the Total Environment 613-614,10-19. An upcoming interlaboratory test (ring-test), based on improvements of the test system, should be the basis for guideline development, and the OECD is planning to publish a final guideline for this type of study in 2023/24.

Personally, I have been working on the development of this test system since 2011 and wrote my PhD thesis on this subject. At ibacon, I am now implementing this method and its latest developments.

ibacon is preparing to offer this test in the form of standard studies and can provide interested clients with advice on study performance. Our study directors offer valuable knowledge on the technical infrastructure of the different plant species, and we have a solid track record with liquid scintillation counting and combustion of plant material together with trapping of generated radioactive CO2.

We are confident that the combination of our first-class facilities and strong in-house expertise will mean that ibacon can provide unrivalled know-how for this exciting new study type.

For more information about this new study type, click on the dowload button and discover the scientific background.