ISO 846:2019

Overview - ISO 846:2019 (Plastics - Evaluation of the action of microorganisms)

ISO 846:2019 defines laboratory methods to evaluate how microorganisms (fungi, bacteria and soil microflora) affect plastics. It is an empirical test standard focused on biodeterioration (visual attack, mass loss, or changes in physical properties), not on biodegradability or natural-fibre composite decay. The third edition (2019) updates specimen size, test design and assessment aids to improve reproducibility across test laboratories.

Key topics and technical requirements

• Scope and applicability
  • Applies to non‑porous plastics with even, cleanable surfaces (excludes porous materials such as plastic foams).
  • Aims to detect deterioration caused by fungal, bacterial or soil microorganisms.
• Test methods
  • Method A - Fungal-growth test: inoculation and incubation with selected test fungi; assessment of fungal colonization and physical attack.
  • Method B: deleted in this edition.
  • Method C - Resistance to bacteria: procedures to evaluate bacterial effects on plastics.
  • Method D - Soil‑burial test: exposure to microbially active soil to assess biodeterioration.
• Assessment criteria
  • Visual examination (surface growth, staining, discolouration)
  • Change in mass (mass loss or gain after cleaning)
  • Changes in other physical properties (mechanical or surface properties as appropriate)
• Standardized specimen control and harmonization
  • Specimen size standardized to (50 mm ± 1 mm) square to reduce edge‑effect variability.
  • Uses the same test fungi as IEC 60068‑2‑10 for alignment with electrotechnical testing.
  • Introduces stainless steel negative controls, positive control specimens (for fungistatic assessments), a grid for objective surface-growth evaluation, and a water reservoir approach to maintain ~95% ± 5% relative humidity during incubation.
• Safety and competence
  • Tests involve potentially hazardous microorganisms; only trained microbiology personnel should perform them and follow biosafety and sterilization codes (see IEC 60068‑2‑10 and ISO 7218).

Practical applications - who uses ISO 846:2019

• Plastics manufacturers - product development and quality control to assess resistance to microbial attack.
• R&D and materials laboratories - evaluate formulation changes, additives, and antimicrobial treatments.
• Building materials and construction specifiers - verify suitability of plastic components exposed to humid environments.
• Test houses and certification bodies - provide standardized, reproducible reports for procurement and compliance.
• OEMs and end‑users - assess long‑term serviceability where microbes may impact appearance, performance or hygiene.

Related standards

• IEC 60068‑2‑10 (uses the same fungal strains and similar test philosophy)
• ISO 7218 (microbiological testing practices)
• Referenced materials and mechanical-property standards cited within ISO 846 for test-specific measurements.

Keywords: ISO 846:2019, plastics microorganism evaluation, biodeterioration testing, fungal growth test, soil‑burial test, fungistatic testing, plastics testing standards.