Test No. 301: Ready Biodegradability
It’s actually not just one test, but a group of six related test guidelines for assessing the ready biodegradability of chemicals in an aerobic aqueous medium. Each method has its own strengths and weaknesses, and the choice of which method to use depends on the specific properties of the test substance.
Here's a quick overview of the six methods under OECD 301:
- DOC Die-Away: Measures the decrease in dissolved organic carbon (DOC) during biodegradation.
CO2 Evolution (Modified Sturm Test): Measures the amount of carbon dioxide (CO2) produced during biodegradation.
MITI (I) (Ministry of International Trade and Industry, Japan): Similar to DOC Die-Away but uses a different mineral medium and inoculum.
Closed Bottle: Measures oxygen consumption during biodegradation in sealed bottles.
Modified OECD Screening: A rapid and simple test using a small amount of test substance and inoculum.
Manometric Respirometry: Measures oxygen consumption in real-time using specialized equipment.
Common features of all methods:
- Conducted under aerobic conditions (in the presence of oxygen) in an aqueous medium (water).
- Use a mixed culture of microorganisms from activated sludge.
- Measure biodegradation over a 28-day period.
- Express results as a percentage of the theoretical maximum biodegradation (ThBOD or ThCO2).
Applications:
Used to:
- Assess the potential persistence and environmental impact of chemicals.
- Predict the fate of chemicals in wastewater treatment plants and surface waters.
- Support chemical registration and safety assessment.
Benefits:
- Standardized and reliable methods.
- Relatively simple and cost-effective.
- Provide valuable data for environmental risk assessment.
Limitations:
- May not be suitable for all types of chemicals, especially volatile or poorly water-soluble substances.
- Do not provide information on the specific biodegradation pathways or the organisms involved.
- Cannot predict the long-term fate and effects of chemicals in complex environmental conditions.
Overall, the OECD 301 test guidelines are valuable tools for screening chemicals for ready biodegradability and contribute to the development of safer and more environmentally friendly products.
