Toxicity of additives present in conventional and biodegradable plastics on soil fauna: a case study of the root lesion nematode Pratylenchus neglectus

Plastic pollution in terrestrial environments is a growing concern, with an increasing focus on the impact of plastic additives on soil ecosystems. We evaluated the impact of additives from conventional plastics (ACP) and biodegradable plastics (ABP) on the soil nematode, Pratylenchus neglectus. The additives represented five functional classes (antioxidants, colourants, flame retardants, nucleating agents, and plasticisers). P. neglectus exhibited concentration-dependent mortality when exposed to the additives, with Tartrazine, an ABP colourant, inducing higher mortality compared to the conventional counterpart. No significant changes in the locomotory patterns of P. neglectus were observed, whereas oxidative stress significantly increased in response to all assistive treatments. Exposure to most of the additives resulted in a significant decline in nematode reproduction; ACPs generally caused more severe effects than ABPs. Our findings highlight a complexity in how plastic additives impact soil organisms and challenge the assumption that ABPs may be universally safer for ecosystems. The study emphasises the importance of conducting ecotoxicological assessments of specific ABPs on important species to inform the design of environmentally sustainable plastics. The results also suggest that P. neglectus could serve as a valuable sentinel organism for evaluating the ecological impacts of plastic pollution in soil.