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Challenges in Calculating the Mean Measured Concentrations for Algal Growth Inhibition Test

By May 30, 2024June 3rd, 2024No Comments

We are pleased to share the poster made in collaboration with Symrise and presented by our CEO Stefan Höger at SETAC in 2024.

Title: “Challenges in Calculating the Mean Measured Concentrations for Algal Growth Inhibition Test According to OECD Test Guideline 201 – And What About the Toxicity?

Algae are important test species for the risk assessment of, among others, industrial chemicals under REACH. Some of the chemicals show challenging characteristics being e.g. hardly water soluble, unstable, volatile or very toxic for water organisms. In experiments with rapidly degradable substances, recovery can be very low after a test period of 72 hours. For these substances, it is advisable to measure the degradation or loss of the substance every 24 hours, to obtain data at test start, after 24, 48 and 72 hours. In case of very low values measured at 24-hour intervals (< limit of quantification, LOQ), the mathematical equation chosen to calculate the average concentrations measured is crucial, as it gives them more or less weight. Therefore, the challenge is to use these values correctly to calculate the mean value which is important for risk assessment. To our knowledge, there are still no binding specifications from the authorities as to how this should be calculated. It should also not be forgotten that the toxicity and thus the growth of algae can be affected by degradation or offgassing of the substance. All this should be considered when creating a guidance document, the first step of which could be this poster.