Ecotoxicity assessment of biodegradable plastics verifies that degradable materials, their additives, and their degradation residues cause no measurable harm to aquatic, soil, and compost ecosystems. Guided by EN 13432, ASTM D6400, ISO 23517, and GB/T standards, accredited third-party laboratories evaluate samples ranging from resins and finished products to composts, soils, sediments, and leachates. This article outlines the scope, test items, organism models, methodologies, and applications that support certification and eco-safe product development.
Technical Overview
Ecotoxicity assessment of biodegradable plastics is the systematic evaluation of adverse effects that a material, and everything it releases during degradation, may exert on organisms in the compartments where it is designed to break down: industrial and home compost, agricultural soil, freshwater, and marine environments. It constitutes a mandatory eco-safety pillar alongside biodegradation and disintegration testing in compostability schemes such as EN 13432 and ASTM D6400, and in product specifications such as ISO 23517-1 for biodegradable mulch films and GB/T 38082 for biodegradable plastic shopping bags.
Although complete biodegradation converts polymer carbon into carbon dioxide, water, and microbial biomass, the degradation pathway can liberate oligomers, residual monomers, plasticizers, processing aids, inks, adhesives, and heavy-metal-based pigments, together with transient micro- and nanoplastic fragments. Ecotoxicity testing quantifies whether these releases remain below effect thresholds for representative organisms across trophic levels, providing scientific evidence that a material is not only biodegradable but also environmentally safe.
Accredited third-party laboratories typically apply a tiered testing strategy: chemical characterization of regulated substances first, followed by acute organism-level tests, chronic or sublethal tests where warranted, and finally matrix tests performed directly on compost or soil containing the disintegrated test material. Studies are conducted under Good Laboratory Practice with method validation aligned to ISO/IEC 17025 accreditation requirements, ensuring data quality suitable for certification bodies and regulatory submissions.
Testing Samples
Raw Materials, Resins, and Additives
Pellets and powders of base polymers such as PLA, PBAT, PBS, PHA, and starch blends, as well as masterbatches and additive concentrates, are tested to characterize the intrinsic hazard profile of a formulation before product integration. This allows formulators to identify problematic additives early in development.
Finished Products and Semi-Finished Items
Test pieces are cut from commercial articles as sold, including packaging films, carrier bags, straws, cutlery, coffee capsules, coated paper and board, nonwovens, fibers, and agricultural mulch films. Testing the finished article captures contributions from inks, adhesives, laminates, and printing layers that are absent from the base resin.
Biodegradation Residues and End-of-Life Matrices
Compost generated in controlled biodegradation tests such as ISO 14855-1, ASTM D5338, or GB/T 19277.1, soils from ISO 17556, ASTM D5988, or GB/T 22047 trials, and marine sediments from ISO 19679 or ASTM D6691 exposures are collected after the degradation phase. Disintegration residues from ISO 16929 or ISO 20200 procedures are similarly retained. These aged matrices are tested directly on terrestrial organisms to satisfy the eco-safety requirements of EN 13432 and ASTM D6400.
Leachates, Extracts, and Eluates
Aqueous extracts prepared at defined material-to-liquid ratios, and eluates obtained from aged compost or soil using leaching procedures consistent with EN 12457, serve as test media for aquatic toxicity assays. This route is essential when evaluating runoff scenarios and the aquatic mobility of degradation intermediates and additives.
Testing Items
A comprehensive assessment program combines organism-level bioassays with chemical screening. Typical test items include the following:
- Aquatic acute toxicity: algae growth inhibition, daphnia immobilization, fish acute lethality, luminescent bacteria inhibition, and activated sludge respiration inhibition.
- Aquatic chronic and sublethal toxicity: daphnia reproduction, fish embryo toxicity, and duckweed growth inhibition.
- Terrestrial toxicity: earthworm acute toxicity and reproduction, collembolan reproduction, plant seedling emergence and growth, root elongation, and soil microbial activity endpoints such as respiration, nitrification, and biomass.
- Compost eco-safety: seed germination and plant biomass production on finished compost containing degraded test material.
- Chemical screening: regulated heavy metals and elemental contaminants, including lead, cadmium, mercury, chromium, and arsenic, verified against the limit values specified in EN 13432 and ASTM D6400.
- Supporting parameters: pH, electrical conductivity, dry solids, and carbon-to-nitrogen ratio of test matrices, required for the validity of plant and invertebrate assays.
- Advanced endpoints where required: genotoxicity screening using the umu test according to ISO 11350, and particle-specific testing of microplastic fragments generated during disintegration.
Testing Methods
Aquatic Toxicity Testing
Freshwater assays follow internationally standardized protocols: growth inhibition of unicellular green algae over 72 hours per ISO 8692 or GB/T 21805, immobilization of Daphnia magna over 24 to 48 hours per ISO 6341 or GB/T 21830, acute lethality in fish over 96 hours per ISO 7346, and fish embryo toxicity with zebrafish per ISO 15088 as a vertebrate-sparing alternative. Bacterial endpoints include inhibition of Vibrio fischeri bioluminescence per ISO 11348 and inhibition of activated sludge respiration per ISO 8192, the latter protecting wastewater treatment processes. For marine claims, marine algal growth inhibition per ISO 10253 and acute toxicity to marine copepods per ISO 14669 complete the profile. Endpoints are reported as EC50, ErC50, LC50, or NOEC values derived from geometric concentration series with concurrent negative and, where applicable, reference-toxicant controls.
Terrestrial Toxicity Testing
Soil-dwelling organisms are exposed in standardized artificial or natural soils spiked with test material, residues, or aged matrices. Acute earthworm toxicity over 14 days and reproduction over 56 days are conducted with Eisenia fetida or Eisenia andrei per ISO 11268-1 and ISO 11268-2, with control mortality not exceeding 10 percent. Collembolan reproduction with Folsomia candida follows ISO 11267. Plant assays per ISO 11269-2 evaluate seedling emergence and biomass with at least one monocotyledonous and one dicotyledonous species, while ISO 11269-1 addresses root elongation. Microbial function is assessed through basal respiration per ISO 16072, potential nitrification per ISO 15685, and microbial biomass per ISO 14240, detecting sublethal disruption of nutrient cycling.
Compost Ecotoxicity per EN 13432 and ASTM D6400
The eco-safety module of compostability schemes is performed on the final compost obtained after disintegration of the test material. Seedling emergence and subsequent biomass production of two higher plant species, commonly garden cress and summer barley, are compared between test compost and blank control compost. Acceptance requires germination and biomass of at least 90 percent of the blank values, in combination with regulated element concentrations below the specified limit values. ISO 23517-1 extends this logic to mulch films, defining pass criteria based on plant growth and soil invertebrate tests on soils containing degraded film residues.
Sample Preparation and Data Evaluation
Solid samples are dried, milled, and sieved to defined particle fractions, then incorporated into matrices at specified rates or extracted into aqueous media at fixed ratios. Concentration series follow geometric spacing with at least five levels and adequate replication. Effect concentrations are calculated by probit or logistic regression, while NOEC and LOEC values are derived through analysis of variance followed by multiple comparison procedures such as Dunnett testing. All studies document organism source, age class, test conditions, validity criteria, and deviations to support independent technical review.
Applications
Ecotoxicity assessment data underpin certification, compliance, and product development decisions across the biodegradable plastics value chain:
- Compostability certification supporting EN 13432, ASTM D6400, and ASTM D6868 conformity for packaging, foodservice items, and coated paper products.
- Verification of biodegradable mulch films against ISO 23517-1, combining soil biodegradation per ISO 17556 or ASTM D5988 with terrestrial ecotoxicity endpoints for agricultural market access.
- Substantiation of marine and multi-environment degradation claims, pairing ISO 19679, ISO 18830, or ASTM D6691 biodegradation data with marine organism toxicity results.
- National market compliance in China under GB/T 20197, GB/T 38082, GB/T 19277.1, and GB/T 22047, including the ecotoxicological requirements referenced by these specifications.
- Research and development support, including comparative safety benchmarking of formulations, additive substitution studies, and qualification of raw material suppliers.
- Brand due diligence, eco-label substantiation, and batch-level quality control releases for retailers and converters.
FAQ
Does biodegradable automatically mean non-toxic?
No. Biodegradability describes polymer conversion by microorganisms, while ecotoxicity describes biological hazard. A fully biodegradable material can still release toxic additives, residual monomers, or degradation intermediates, which is why EN 13432, ASTM D6400, and ISO 23517 treat eco-safety testing as an independent pass criterion.
Is the plastic itself tested, or the compost and soil after degradation?
Both approaches are used. Parent materials and their aqueous leachates are tested to characterize intrinsic hazard, while aged compost and soil matrices generated in biodegradation trials are tested directly on plants and soil organisms, because certification schemes are specifically concerned with the end-state of the degraded material.
Which organisms and pass criteria are most common?
The core battery includes algae, daphnia, fish or fish embryos, luminescent bacteria, earthworms, and higher plants. The most frequently cited acceptance criterion is the EN 13432 and ASTM D6400 requirement of at least 90 percent seed germination and plant biomass relative to blank compost, together with heavy-metal concentrations below specified limits.
How long does a full assessment take?
Aquatic acute tests complete within two to ten days, plant and earthworm acute tests within two to three weeks, and reproduction assays such as ISO 11268-2 require up to eight weeks. Where the compost matrix must first be generated through a controlled biodegradation phase of up to six months, the overall program should be planned across two full testing cycles.
Which standards should a testing plan reference?
A robust plan references the certification or product specification, such as EN 13432, ASTM D6400, ISO 23517-1, or GB/T 38082, together with the corresponding organism-level method standards from the ISO 6341, ISO 8692, ISO 11268, ISO 11269, and GB/T 21805 series, executed by an ISO/IEC 17025-accredited third-party laboratory.
Do microplastic fragments require special testing?
Yes. Fragments generated during disintegration can be dosed as particles in aquatic and terrestrial assays, often with accelerated aging or UV pre-weathering to simulate environmental exposure. Because harmonized pass criteria for particle effects are still evolving, study designs should be agreed in advance with the receiving certification body or regulator.