OECD 301A

Determine the ready biodegradability of organic compounds

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Abstract

The OECD 301A DOC (dissolved organic carbon) Die-Away Test is one of the methods used to determine the ready biodegradability of organic compounds. It is designed to assess the degradation rate of a material by microorganisms in an aerobic aqueous environment. This test is quite useful in evaluating the impact of chemicals on the environment, helps manufacturers understand the behavior of their products in natural ecosystems and ensures compliance with environmental safety standards.

The DOC Die-Away test is conducted over a 28-day period and forms part of a structured plan that allows the DOC in the sample to be continuously monitored. The decrease of DOC concentration indicates organic material biodegradation, thus presenting a clear view of the compound’s biodegradability.

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OECD 301 A test conditions

  • The OECD-301A test must be conducted under specific conditions to ensure consistency and reliability of the results. 
  • The test substance should be non-volatile and soluble in water with a concentration of at least 100 mg/L. 
  • The temperature must be maintained at 22°C ± 2°C, and the test should be run in the dark or under very dim light to avoid photodegradation. 
  • The microbial inoculum used during the test can be sourced from natural environments such as wastewater, surface water, or soil. This ensures that a diverse microbial community capable of degrading many kinds of compounds exists in the inoculum.

OECD 301 A test requirements

  • To ensure accuracy, the OECD-301A test further requires that the DOC concentration at the commencement of the test should lie between 10-40 mg/L. 
  • The inoculum concentration used for the microorganisms should also be low typically, not more than 30 mg/L of suspended solids to avoid interference with the test results. 
  • A blank control without the test substance is also run to eliminate any background DOC removal that may arise through microbial action alone. In parallel to this, a known readily biodegradable reference compound is tested to validate the procedure.

OECD 301 A test methodology

The test procedure involves the following steps aimed at ensuring consistency and reproducibility:

  • A measured volume of inoculated mineral medium is prepared, containing a known concentration of the test substance (10-40 mg DOC/l), as the sole source of organic carbon.
  • The solution is aerated in the dark or under diffuse light at 22 ± 2°C.
  • Degradation is followed by DOC measurements taken at appropriate intervals over a period of 28 days.
  • The degree of biodegradation can be quantitatively determined by the amount of DOC removed relative to the amount present initially, with corrections made for any level of removal in the blank inoculum control.
  • Further chemical analysis of the parent compound at both start and end of the incubation may also be used to quantify primary biodegradation.

Efficacy criteria

The test shall be regarded as valid if the reference compound demonstrates at least 70% DOC removal and the test substance must achieve this threshold within the duration of 28 days.

Importance of OECD 301A test

The OECD 301 A test is crucial to industries that manufacture and deal with chemicals as it provides information about the environmental fate of their products. Having a thorough understanding of how a product degrades, helps manufacturers make informed decisions about their product designs, disposal methods and regulatory compliance. Testing is also crucial for ascertaining that these substances when released into the environment do not persist for long or cause harm to the ecosystem.

Test organisms

The microorganisms used for the OECD-301A test are often sourced from activated sludge, sewage effluent, surface waters, or soils. This provides a diverse group of microorganisms that can potentially break down a large variety of organic materials. These microbes are active under aerobic conditions where oxygen is used to oxidize the organic carbon available within the test substance.

Test product information

The OECD-301A test is applicable to a broad variety of organic chemicals, including industrial process chemicals, personal care products, as well as pharmaceuticals. In particular, the OECD-301A test is best suited for water-soluble, non-volatile substances as these properties allow for the accurate determination of DOC levels throughout the test.

Compliance and industry standards for OECD 301A

Companies must comply with biodegradability standards to meet environmental regulations and ensure that their products are safe for the environment. The OECD-301A test aligns with international requirements and standards for environmental safety, is widely recognized and adopted by regulatory agencies worldwide, including the European Chemicals Agency (ECHA)  and the U.S. Environmental Protection Agency (EPA). 

Advantages of OECD-301A test standard

Comprehensive assessment

The test offers a complete evaluation of the biodegradability of the substance, thus offering manufacturers an essential insight into the potential effect their product may have on the environment.

Easily accessible

The test method does not require highly sophisticated or intrusive techniques and is thus accessible to a range of laboratories.

Conclusion

The DOC Die-Away Test is a crucial tool for assessing the biodegradability of organic substances. It provides valuable data that helps companies comply with environmental regulations, make informed decisions about product design, and minimize their ecological footprint. By using this standardized method, companies can ensure that their products are safe for the environment while meeting global biodegradability standards.

At Microbe Investigations Switzerland, we offer expert OECD 301A DOC Die-Away testing to help ensure your products meet environmental compliance standards. Partner with us to accurately assess the biodegradability of your substances and contribute to a safer, more sustainable future. Contact us today to learn more about our testing services or to schedule your consultation.

Frequently Asked Questions

DR. Martinoz Scholtz

MIS Labs
1. What types of substances are tested under OECD-301A?

The OECD 301A can be used to test water-soluble, non-volatile, and organic substances.

2. How does the OECD 301A test work?

The test measures the decrease of DOC (dissolved organic carbon) in a solution of the test substance during 28 days to assess biodegradation.

3. What are the key criteria for a substance to pass the OECD-301A test?

To be classified as readily biodegradable, the material has to show that at least 70% DOC is removed in 28 days.

4. What is the significance of the 10-day window in the OECD-301A test?

The 10-day window for the OECD-301A test starts at 10% biodegradation and 70% of the DOC has to be removed within the window of that time to be classified as readily biodegradable.

5. What are the differences between OECD 301A and other OECD 301 tests?

Different methods are used for each OECD 301 test. For example, OECD 301B measures the evolution of CO2, while for 301A it measures DOC removal.

6. Can OECD 301A be used to test non-organic substances?

No, the test is designed for organic compounds that serve as a carbon source for microorganisms.

7. How is dissolved organic carbon (DOC) measured in the OECD-301A test?

DOC is measured with specific analysers that give an indication of the concentration of the organic carbon in the solution during the entire test duration.

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