New method to evaluate the risk of microplastics in soils

Published On: February 15, 2024

Researchers from IMDEA Water and Wageningen University & Research (WUR, Netherlands) have evaluated for the first time the ecological risk of microplastics in soils considering concentration alignment and data quality criteria.

Photo by Raffaella Meffe and Virtudes Martínez HernándezThe diversity and complexity of microplastics makes difficult to assess their risks to life in the soil. “Our concern began with the discovery of plastic in the oceans. Later, attention was paid to its adverse effects on rivers and lakes”, says Dr. Paula Redondo-Hasselerharm, from IMDEA Water. «Only recently has the effects on the soil begun to be evaluated”. The institute participates in several projects focused on evaluating the fate and effects of microplastics in soil.

According to Professor Bart Koelmans, researcher at WUR, “studies on the exposure and effects of microplastic particles in soil have so far compared apples and pears. Microplastics in soil are very diverse and differ greatly from those used in toxicity tests”. For this reason, he explains, in this work a method has been applied for the first time to correct this difference. For example, if the negative effect is caused by the volume of ingested particles, the quantity of microplastics in the soil and in toxicity tests is calculated to make an appropriate comparison.

Redondo-Hasselerharm adds that it has been observed how these particles differ depending on their origin: “There are differences between those coming from atmospheric deposition, or those that enter through the application of compost or sewage sludge.” In the study, four risk assessments, one for each source, were carried out.

An important finding of this study is that most soils around the world are not yet at risk. However, in some places, the concentration of microplastics is higher than the threshold effect, so they could be at a risk. Scientists agree that the amount of microplastics released into the environment will increase in the future and with it, the number of places where concentrations of microplastics in soil exceed safe limits for the species. In addition, the fragmentation of plastic encourages the generation of increasingly smaller particles, which means that a greater number of species have the capacity to ingest them.

Quantitative methods like these will provide information about future risks from microplastics. Analytical procedures to detect plastic particles and methods to assess their impact are still being developed. Therefore, this new technique constitutes a valuable tool.

IMDEA Water has participated in several national and international projects to study the fate and effects of microplastics in the soil, such as IMPASSE (Project PCIN-2017-016 funded by MCIN/AEI /10.13039/501100011033 and co-funded by the European Union) or µNanoCare, (Grant RTC2019-007261-5 funded by MCIN/AEI/10.13039/501100011033). Now, the institute is part of the international consortium H2020 PAPILLONS (GA n. 101000210) and coordinates the national project AddiPlaS (Grant PID2022-140011OB-I00 funded by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe).

Paula E. Redondo-Hasselerharm, Andreu Rico, Esperanza Huerta Lwanga, Cornelis A.M. van Gestel, Albert A. Koelmans. Source-specific probabilistic risk assessment of microplastics in soils applying quality criteria and data alignment methods. Journal of Hazardous Materials, Volume 467, 2024, 133732, ISSN 0304-3894,

Risk of microplastics in soils

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