ISO 21427-1:2006

Overview

ISO 21427-1:2006 - "Water quality - Evaluation of genotoxicity by measurement of the induction of micronuclei - Part 1: Evaluation of genotoxicity using amphibian larvae" specifies a laboratory micronucleus assay using amphibian larvae (mainly Xenopus laevis, also Pleurodeles waltl) to assess genotoxic effects in aqueous samples. The method applies to aqueous effluents, leachates, eluates (soils, industrial waste, sludges), surface and ground water, and water‑soluble substances, providing a standardized protocol for environmental genotoxicity screening.

Key topics and technical requirements

• Test organism and stage: Larvae of Xenopus laevis (recommended) or Pleurodeles waltl; tests start at Nieuwkoop and Faber stage 50 (larvae ~20–27 mm).
• Exposure regime: Continuous exposure for 12 days to a range of sample concentrations, with paired negative (blank) and positive controls to validate biological responsiveness.
• Endpoint: Frequency of erythrocytes with micronuclei, scored per 1 000 erythrocytes (expressed in ‰), using microscopic examination (immersion lens, high magnification).
• Positive control: Cyclophosphamide monohydrate (reference substance); typical concentration referenced in the standard (analytical quality).
• Test conditions: 12 h light / 12 h dark cycle; temperature controlled at 22 °C ± 1 °C; defined feeding, anaesthesia and staining procedures.
• Sample handling: Sampling, storage and transport guidance (ISO 5667-16 referenced); interval between collection and lab receipt ≤ 24 h. For solids, EN 12457-2 leaching protocol is required (eluates must not be filtered), and eluates stored in the dark at 4 °C ± 3 °C and used within specified time limits.
• Quality and validity criteria: Requirements for batch size, preconditioning of larvae, solvent controls (e.g., DMSO), and statistical processing of results (example methods provided in annexes).

Applications

• Environmental monitoring of genotoxicity in surface and groundwater.
• Assessment of industrial effluents, sewage sludges, landfill leachates, and contaminated soils (via eluates).
• Regulatory compliance testing and risk assessment when screening for DNA‑damaging contaminants in aquatic environments.
• Research and ecotoxicology studies comparing genotoxic potential of waterborne substances.

Who should use this standard

• Environmental testing laboratories and contract bioassay labs
• Water quality and wastewater treatment authorities
• Regulatory agencies and compliance units
• Ecotoxicologists and environmental researchers conducting genotoxicity assessments

Related standards

• ISO 21427-2 (Part 2: mixed population method using V79 cell line)
• ISO 5667-16 (sampling - guidance on biotesting)
• EN 12457-2 (leaching of solid wastes)
• ISO 7346 series (acute fish toxicity methods)

Keywords: ISO 21427-1:2006, genotoxicity, micronuclei, amphibian larvae, Xenopus laevis, Pleurodeles waltl, water quality testing, effluent screening, leachate testing, aquatic genotoxicity.