Overview
EN ISO 11350:2025 - "Water quality - Determination of the genotoxicity of water and waste water - Salmonella/microsome fluctuation test (Ames fluctuation test)" - specifies a standardized microbiological method for assessing the genotoxic potential of aqueous samples. The method applies a fluctuation version of the Ames test using bacterial strains Salmonella enterica serovar Typhimurium TA98 and TA100 to detect point mutations (base-pair substitutions and frameshifts) that restore histidine biosynthesis. Applicable sample types include fresh water, waste water, drinking water (often after pre-concentration), leachates, eluates, pore water and aqueous extracts.
Key topics and requirements
- Test principle: fluctuation assay variant of the Ames test using TA98 and TA100 to quantify revertant growth as an indicator of mutagenicity.
- Metabolic activation: use of an S9 fraction and S9 mix (rat liver-derived metabolic activation system) for detection of pro-mutagens.
- Sample preparation: sterile filtration and optional pre-concentration or extraction for low-level contaminants; definitions for dilution levels and Lowest Ineffective Dilution (LID).
- Controls and validity: required negative controls, positive controls (mutagens in DMSO) and procedural checks (genotype verification, cytotoxicity assessment).
- Procedures and materials: detailed requirements for overnight cultures, media, reagents, plate layouts, inocula and measurement of revertant wells.
- Data handling: calculation of induction rates, cytotoxicity, statistical assessment and reporting requirements; annexes include precision data and statistical guidance.
- Limitations and interferences: bacteriotoxic effects can mask genotoxic responses; sterile filtration may remove particle-bound genotoxins.
Applications and users
EN ISO 11350:2025 is intended for:
- Environmental and water testing laboratories performing genotoxicity screening of influents, effluents and ambient waters.
- Wastewater treatment operators assessing process performance and environmental compliance.
- Regulatory agencies and public health authorities requiring standardized methods for water quality and ecotoxicology.
- Researchers and contractors evaluating chemical mixtures, leachates, and remediation outcomes.
Practical value: provides a reproducible, internationally harmonized protocol to detect mutagenic contaminants and support risk assessment, monitoring programs and source-control measures.
Related standards
- ISO 11350:2012 (original International Standard adopted unchanged as EN ISO 11350:2025)
- Normative references within the standard: ISO 3696 (water for analytical use), ISO 7027 (turbidity)
- Note: ISO 13829 is referenced for DNA-crosslinking agents; consult for complementary genotoxicity assays.
For laboratories and stakeholders prioritizing water quality and environmental safety, EN ISO 11350:2025 provides a robust, validated approach for detecting genotoxic hazards using the Ames fluctuation test.
