Overview
EN ISO 21427-2:2009 (ISO 21427-2:2006) describes a standardized in vitro method for evaluating water quality by measuring genotoxicity through the induction of micronuclei in the mammalian V79 cell line (Chinese hamster). The assay detects clastogenic and/or aneugenic activity of water and wastewater samples by comparing the frequency of micronucleated cells after exposure with and without metabolic activation (S9 mix). The standard is intended for qualified laboratory personnel and specifies test conditions, controls and reporting requirements.
Key topics and requirements
- Test principle: Exposure of V79 cells to undiluted and diluted test samples; detection of increased micronucleated cell frequency indicates chromosomal damage (micronuclei from lagging chromosome fragments or whole chromosomes).
- Metabolic activation: Use of an S9 fraction (9 000 g liver supernatant from induced rats) combined with a cofactor solution (S9 mix) when needed to reveal pro‑genotoxins.
- Exposure times: Typical exposure is 24 h; with S9 mix a 4 h exposure is specified.
- Interferences and limits: Monitor and control pH and osmolality; avoid artifacts from precipitation, phagocytosis or severe cytotoxicity. If pH shifts occur, adjust to pH 7.0 ± 0.2. Highest test concentrations must not cause unacceptable osmolality changes or excessive cytotoxicity.
- Quality and reproducibility: Sections cover reagents, apparatus, test facility criteria, procedures, evaluation and reporting. The standard includes annexes on S9 preparation, BrdU method, evaluation schemes and precision data.
- Lab practices: Use reagent‑grade chemicals, water conductivity ≤ 5 µS/cm, and standard sterilization (e.g., autoclave 20 min at 121 °C ± 2 °C). Tests must be run by trained staff following safety practices.
Applications and users
- Environmental laboratories performing routine or investigative screening of drinking water, surface water, groundwater and wastewater for genotoxic contaminants.
- Water utilities and treatment operators assessing treatment efficiency and potential genotoxic risks.
- Regulatory agencies and monitoring programs for compliance and risk assessment.
- Research institutions and contract testing organizations (CROs) developing environmental toxicology data or validating remediation/pretreatment processes.
Practical uses include screening water samples for genotoxicants, comparing treatment options, and contributing data for human and ecological risk assessments.
Related standards
- ISO 21427-1 (Part 1: amphibian larvae method) - the ISO 21427 series covers alternative biological genotoxicity assays.
- ISO 5667-16 - guidance on sampling for biotesting of water.
Keywords: EN ISO 21427-2:2009, ISO 21427-2, water quality, genotoxicity, micronucleus test, V79 cell line, S9 metabolic activation, wastewater testing, in vitro genotoxicity.
