ISO 10229:1994

Overview

ISO 10229:1994 - Water quality: Determination of the prolonged toxicity of substances to freshwater fish - provides a standardized laboratory method for assessing the long‑term, sublethal toxicity of water‑soluble substances to rainbow trout (Oncorhynchus mykiss). The standard specifies procedures to evaluate effects on growth rate after exposures of 14 days and 28 days, and to assign prolonged sublethal toxicity categories (e.g., LOEC / NOEC) under defined test conditions.

Key topics and technical requirements

• Test species and conditions: Uses rainbow trout (single stock), with fish typically 3–5 g at test start; maintained under controlled temperature (12.5–17.5 °C), illumination and water quality.
• Test design: Two-stage approach - a preliminary 96 h LC50 test to set concentration ranges, followed by a final chronic test (minimum five concentrations recommended) with 16 fish per concentration.
• Exposure methods: Both flow‑through and semi‑static options are allowed. Flow‑through is preferred for unstable substances; semi‑static requires daily renewal.
• Endpoints and statistics: Primary endpoint is change in growth rate; results reported as NOEC (no observed effect concentration) and LOEC (lowest observed effect concentration). Data may be modelled to derive an ICI0 (10% inhibition concentration).
• Feeding and husbandry: Feeding rates recommended (e.g., ~1% mass/day during pre‑acclimation, 4% during the final test); tanks should be ≥45 L and covered to limit disturbance.
• Analytical considerations: Wherever possible, measure actual test concentrations. Nominal values may be used only when measured concentrations remain within specified limits. Solvent use is limited (≤0.1 ml/L, preferably ≤0.01 ml/L) and solvent controls are required.
• Quality controls: Dissolved oxygen maintained >70% air saturation, pH typically 6.7–8.5, and stock/solution handling rules (e.g., limits on stock volume additions) to ensure test reliability.
• Marking and handling: Optional marking (e.g., freeze‑branding) and other fish handling procedures are described to allow individual recognition without stressing animals.

Applications and users

ISO 10229:1994 is used by:

• Ecotoxicology laboratories performing chronic fish tests
• Regulators and environmental agencies assessing chemical or effluent impacts on freshwater biota
• Industry and consultants conducting environmental risk assessments and toxicity categorization
• Research groups studying sublethal effects on fish growth

Practical applications include classification of prolonged sublethal effects, screening of industrial chemicals and wastewaters, and informing environmental monitoring and management decisions.

Related standards

• ISO 7346‑2: 1984 - acute lethal toxicity, semi‑static method
• ISO 7346‑3: 1984 - acute lethal toxicity, flow‑through method

Keywords: ISO 10229:1994, water quality standard, prolonged toxicity, rainbow trout, Oncorhynchus mykiss, chronic toxicity test, LOEC, NOEC, growth rate, flow‑through, semi‑static.