ISO 16240:2005

Overview

ISO 16240:2005 specifies a standardized method to determine the genotoxicity of water and wastewater using the Salmonella/microsome test (Ames test). The method uses two bacterial strains, Salmonella typhimurium TA100 and TA98, and requires sterile filtration of samples before testing. ISO 16240:2005 is intended to detect genotoxic substances present in the filtered aqueous phase only and is not applicable to genotoxic agents bound to retained particles.

Key topics and technical requirements

• Test organisms: Salmonella typhimurium strains TA100 and TA98 as mutation indicators.
• Sample preparation: Mandatory sterile filtration; only dissolved (aqueous-phase) genotoxins are detected.
• Metabolic activation: Use of an S9 fraction / S9 mix (liver-derived metabolic activation, Annex B) for ± activation conditions.
• Controls: Negative control (dilution water) and positive controls (known mutagens dissolved in DMSO) to verify assay sensitivity.
• Endpoints and metrics:
  • Number of revertants (mutant colonies) per plate.
  • Titre determination to assess bacterial viability and bacteriotoxic effects of samples.
  • D value (smallest dilution at which no positive increase in mutants is detected) used for assessment.
• Interferences and limitations: Bacteriotoxic samples can reduce viable bacteria and produce false positives or negatives; particles and adsorbed genotoxins are outside scope.
• Procedure and quality: Standard covers reagents and media, apparatus, plate preparation, incubation (48–72 h at 37 °C), colony counting, evaluation criteria, validity criteria and required documentation (test report).
• Safety & competence: Tests must be run by trained personnel following laboratory safety practices.

Applications and who uses it

ISO 16240:2005 is applied by:

• Environmental and public health laboratories performing water quality and wastewater monitoring.
• Regulatory agencies assessing genotoxic contamination in surface water, effluents or treated wastewater.
• Industrial and municipal wastewater treatment facilities conducting compliance or impact testing.
• Contract testing laboratories offering Ames test services for environmental samples. Practical uses include screening for mutagenic pollutants, evaluating treatment efficacy, and supporting risk assessment and regulatory compliance for water quality.

Related standards

• ISO 5667 series (sampling guidance): ISO 5667-1, -2, -3, -14, -16 referenced for sampling, preservation and quality assurance.
• ISO/TC 147, Subcommittee SC 5: biological methods for water quality.

Keywords: ISO 16240, Ames test, Salmonella/microsome test, genotoxicity, water quality, wastewater testing, TA100, TA98, S9 mix, sterile filtration, D value.