Are Biobased Microfibers Less Harmful than Conventional Plastic Microfibers: Evidence from Earthworms.

Area of Science:

• Environmental Science
• Ecotoxicology
• Materials Science

Background:

• Biobased plastics are often marketed as eco-friendly alternatives to petrochemical plastics.
• The ecotoxicity of biobased materials, particularly fibers used in textiles and hygiene products, is not fully understood.
• These fibers can enter soil ecosystems via biosolid fertilizers, impacting soil organisms.

Purpose of the Study:

• To compare the lethal and sublethal toxicity of biobased fibers (viscose, lyocell) with petrochemical fibers (polyester).
• To assess the impact of these fibers on the earthworm *Esenia fetida*, a key ecosystem engineer.
• To evaluate the ecotoxicological profile of biobased fibers for their use as plastic alternatives.

Main Methods:

• Chemical characterization of additive-free viscose, lyocell, and polyester fibers.
• Acute toxicity testing (LC20, NOEC) using OECD TG207 (72h filter paper method).
• Sublethal toxicity testing (28-day soil exposure, OECD TG222) at environmentally relevant concentrations (100 mg kg-1).

Main Results:

• Viscose and lyocell exhibited LC20 values of 14.00 and 22.66 mg·L-1, respectively, with NOEC of 0-2.8 mg·L-1.
• Polyester showed LC20 values of 15.6-31.3 mg·L-1 and NOEC of 0-15.6 mg·L-1.
• Viscose significantly reduced earthworm progeny mass; lyocell caused marginal growth reduction linked to increased bioturbation.

Conclusions:

• Biobased fibers (viscose, lyocell) demonstrate greater acute toxicity at high concentrations compared to polyester.
• Sublethal effects on *E. fetida* were broadly similar between biobased and polyester fibers.
• Detailed ecotoxicity assessments are necessary before positioning biobased materials as superior environmental alternatives.