A photo showing how pristine microplastics and/or nanoplastics (MPs/NPs) negatively affect the growth and reproduction of soil invertebrates.

A plant nutrition and fertilizer research team from the Institute of Agricultural Resources and Regional Planning at the Chinese Academy of Agricultural Sciences (CAAS) published their latest findings on the ecotoxicological effects of pristine microplastics and/or nanoplastics (MPs/NPs) on soil invertebrates in Science of the Total Environment on May 15.

In their laboratory studies, researchers summarized how soil invertebrates respond to different sizes, shapes, concentrations and chemical structures of pristine MPs/NPs.

According to Li Zhaojun, a corresponding author on the publication, pristine MPs/NPs have been confirmed to cause a variety of ecotoxicological effects on soil invertebrates, though there remains a huge variation in the results of different studies. Thus, it still remains to be characterized about the reaction of soil invertebrates to different sizes, shapes, concentrations and chemical structures of pristine MPs/NPs.

Li and his teammates selected 1,061 biological endpoints in 56 parallel studies and found that 49 percent of them were significantly affected when exposed to pristine MPs/NPs. The MPs/NPs polymers with chloro and phenyl groups had more of a negative impact on soil invertebrates than other types of polymers.

A majority of studies utilized earthworm and nematode species as model organisms. They discovered that a higher concentration of pristine MPs/NPs appeared to have more adverse impacts on the biological functions and physiological systems of nematodes, but this trend was not confirmed in earthworms.

Meta-analysis showed that pristine MP/NP concentrations higher than 1 g kg−1 in soil may exercise negative impacts on the growth and survival of earthworms and that an MP/NP concentration higher than 1 μg L−1 in water may negatively affect the biological functions and reproductive fitness of nematode species.

The research has further deepened public understanding of the ecotoxicological effects of MPs/NPs in soil environments and will be a valuable reference to future studies.

The research was financially supported by China's National Natural Science Foundation and the Endeavour Fund associated with the Ministry of Business, Innovation and Employment (MBIE) of New Zealand.