Reassessing Whether Biodegradable Microplastics Are Environmentally Friendly: Differences in Earthworm Physiological...

Area of Science:

• Environmental Science
• Ecotoxicology
• Soil Science

Background:

• Plastic pollution is a global environmental crisis, with biodegradable plastics promoted as a sustainable alternative.
• Empirical evidence on the environmental safety and toxicological impacts of biodegradable microplastics remains limited.
• Understanding the ecotoxicity of microplastics is crucial for assessing their environmental risks.

Purpose of the Study:

• To systematically compare the toxic effects of traditional microplastics (polypropylene, polystyrene) and biodegradable microplastics (polylactic acid, polyhydroxyalkanoates) on the haplic phaeozem ecosystem.
• To elucidate the differential mechanisms of toxicity and physiological responses in earthworms exposed to various microplastics.
• To establish a scientific basis for evaluating the ecological risks of microplastic pollution and the environmental friendliness of biodegradable plastics.

Main Methods:

• Comparative analysis of microplastic toxicity using earthworms as a model organism in a haplic phaeozem soil environment.
• Mathematical modeling to analyze earthworm physiological responses, including antioxidant enzymes, detoxifying enzymes, metabolic regulation, and immune enhancement.
• Investigation of specific toxicological impacts such as neurotoxicity (acetylcholinesterase activity) and cellular damage (antioxidant system, cell membrane integrity).

Main Results:

• Biodegradable microplastics (polylactic acid, polyhydroxyalkanoates) exhibit significant toxic effects on the soil ecosystem and earthworm physiology.
• Polylactic acid and polypropylene caused severe damage to the antioxidant system and cell membranes, with distinct detoxification pathways.
• Neurotoxicity was observed, with polylactic acid and polystyrene inducing early effects, while polyhydroxyalkanoates showed late-onset neurotoxicity.

Conclusions:

• Biodegradable plastics are not a primary solution for plastic pollution and pose considerable environmental risks.
• The study provides direct evidence that biodegradable microplastics are not environmentally friendly, challenging previous assumptions.
• A novel path analysis model linking biological responses to soil ecological functions offers a robust framework for assessing microplastic ecotoxicity and environmental safety.