Biodegradability Testing: A Simple Introduction

October 16, 2026

Who are you and what is your role?

Hello, my name is Maura Hall. I am a senior environmental safety scientist at the P&G Fabric and Home Care Innovation Center in Cincinnati, USA.

My job is to help ensure that ingredients used in fabric and home care products are safe for the environment. I work with scientists across environmental chemistry, toxicology, ecology, exposure modeling, and regulatory science.

What does an environmental scientist do?

There is no typical day, which is one of the things I enjoy most about my work. I might review new scientific studies, interpret laboratory data, use computer models, design environmental tests, collaborate with academics, or work with product developers and external laboratories.

A major part of my role is environmental risk assessment. This means bringing together information about what happens to an ingredient after use, how much may enter the environment, and whether those concentrations could affect organisms. Ultimately, we use this information to understand whether ingredients can be used safely in our products.

What is your specialist area?

I specialize in environmental fate and exposure assessment. I study what happens to substances after consumers use them in their homes including where they go and how long they remain. I combine laboratory studies, exposure modeling and other scientific information to understand an ingredients environmental behavior and help assess whether it can be used safely. I also partner with external experts and support ongoing research to strengthen the scientific approaches used to ensure environmental safety of our ingredients.

Can you give an example of an ingredient you have studied?

I’ve studied a wide range of chemistries used in consumer products, including solvents, surfactants, chelants, and water-soluble polymers. Within water-soluble polymers, I’ve studied materials such as polyvinyl alcohol (PVA), polyethylene glycol (PEG), and carboxymethylcellulose (CMC). Understanding the specific material is important because its properties can influence how it behaves in the environment. For example, PVA comes in different grades, including water-soluble grades used in applications such as dissolvable laundry detergent films.

My research looks at how these polymers behave in wastewater treatment systems and the environment, including how they biodegrade, where they go, and ensure they will not negatively impact the environment.

What is biodegradability?

Biodegradability describes the ability of microorganisms found in the environment, such as bacteria and fungi, to break down and use a material for energy and growth through natural biological processes. Ultimately, materials can be converted into carbon dioxide, water, methane and other small nutrients naturally found in the environment. Materials can also be converted into new microbial biomass – for example, allowing more microorganisms to grow, or being used to repair microbial cell walls and/or grow new cells).

When assessing the biodegradability of an ingredient, it is critically important to consider which waste stream it enters e.g. landfill, composter, incinerator, recycling facility, wastewater treatment plant, atmosphere, and how long it resides there. Understanding biodegradability helps scientists determine what happens to a substance after use as it moves through treatment facilities such as wastewater treatment systems and then into the receiving environment, including whether it breaks down and the conditions under which biodegradation occurs.

How is biodegradability tested?

Scientists use different approaches to understand whether and how a substance biodegrades. The appropriate method depends on the properties of the substance and the scientific question being addressed. Standardized screening studies are often used as a starting point, with many additional methods available when more information is needed.

What are standardized biodegradation screening studies and what do the results tell us?

Screening studies provide a standardized way to evaluate biodegradation potential under defined laboratory conditions. Internationally recognized methods that have been reviewed by external experts and accredited by standardization committees globally (and accepted in different regions), include the OECD 301 series of ready biodegradability tests, OECD 310, and related ISO (International Standards Organisation) methods. Depending on the screening method, scientists may measure carbon dioxide production, oxygen consumption, or removal of organic carbon as microorganisms break down and utilize the substance. They have been developed over a period of 50 years with many studies at the time, and since, to ensure their environmental relevance and predictability.

These studies are not meant to provide exact real-world simulations. Instead, they provide a helpful prediction of whether a substance will actually biodegrade in the environment. The studies are meant to evaluate whether microbial communities naturally present in the different environmental compartments have the ability to biodegrade the ingredient. These studies are also designed to provide reproducible information that can be interpreted consistently across substances and laboratories. Meeting the established criteria in an appropriate screening study provides strong evidence of biodegradation potential in the real world.

How are the study duration and pass criteria determined in standard screening tests?

Study duration and pass criteria are based on a proven ability of these standardized tests to predict the biodegradation potential of a test substance in the environment, supported by a large set of data and evidence.

For example, a 28 or 60 day study duration is part of some standardized screening test designs, and is not meant to represent how long a substance remains in the environment. The studies are run in conservative or stressed conditions, and run for longer times (even up to 180days to study continued biodegradation), These studies use much lower levels of microorganisms and much higher levels of ingredients than would naturally be found in the environment. In some screening tests, the ratio of test material to micro-organism is over 2500 times higher than in the real world. This is done to allow scientists to follow biodegradation and mineralization to carbon dioxide, but it does mean we have to run the tests for longer to allow time for the microorganisms to eat such a big meal. It’s like having 100 Thanksgiving or Christmas dinners and you have to eat them all yourself - it takes time!

As regards a “pass criteria” for the lab tests, several standardized screening methods use 60% mineralization in the defined test time as the pass criteria, demonstrating strong potential and prediction to biodegrade in the environment. (Mineralisation means carbon converted to carbon dioxide, or oxygen consumed, as the microorganisms biodegrade the test substance). When screening tests are extended, the test substance continues to biodegrade and mineralise.

In addition, many literature references have shown that some of the test substance can be converted into biomass or energy reserves of the microorganisms. Microorganisms use the test material as “food” (just like we do !) to enable the repair of, for example, cells walls, to grow, or to reproduce. So a 60% mineralization pass does not mean that the remaining 40% persists unchanged in the environment – it means this is the point in the test, with the defined test time, that the material is predicted to biodegrade in the environment – material mineralizing to carbon dioxide, and with some material being converted into biomass.

Due to their easy execution, standardized design, and conservative nature with stressed test conditions, screening studies normally represent the first step in a tiered biodegradation assessment process. Substances that pass the screening test criteria (typically over 60% biodegradation in the specific timeframe) are considered biodegradable from a regulatory viewpoint, (e.g. surfactant biodegradability criteria in the EU Detergent Regulation, biodegradable exemption criteria in the EU microplastics restrictions, biodegradable positioning in the US EPA environmental models). The methods, and pass criteria of 60%, have a long pedigree, steeped in science and with many supporting studies over the years, hence allowing this regulatory and environmental confidence to predict biodegradability.

Not meeting a screening criterion does not necessarily mean that a substance cannot biodegrade or will persist in the environment. When additional information is needed, further scientifically appropriate studies can help provide a more complete understanding of biodegradation.

What other biodegradation tests are available?

Scientists use many additional approaches to evaluate biodegradation depending on the substance and the question being addressed. Extended screening studies can provide additional time for biodegradation, while more environmentally realistic studies and field studies can evaluate biodegradation under conditions that more closely represent actual environmental conditions.

Mechanistic studies can provide information about biodegradation pathways and the microorganisms and enzymes involved. Advanced analytical approaches can also help scientists understand both the disappearance of the starting material and what is formed during biodegradation.

Results from different studies can be considered alongside other relevant scientific information, including environmental monitoring to develop a weight-of-evidence understanding of whether, how and under what conditions a substance biodegrades.

Biodegradation is an active area of science, and methods continue to evolve as analytical techniques and our understanding of different substances and biodegradation processes advances.

Do biodegradable polymers behave differently from biodegradable smaller chemicals?

The final biological endpoint is the same: microorganisms use the material, ultimately converting its carbon into carbon dioxide and new microbial biomass. The main difference can be the pathway by which biodegradation occurs.

Polymers are large molecules, and microorganisms may not be able to take them directly into their cells. Instead, enzymes outside the cell can first break the polymer into smaller fragments. Once the fragments are small enough, microorganisms can absorb and use them for food and energy.

Think of it like a pizza. You would not eat the whole pizza in one bite; you first divide it into smaller pieces. In a similar way, a polymer requires additional breakdown steps before microorganisms can use it.

Polymer properties, microbial communities and test conditions can influence how effectively biodegradation is captured in a particular study. This is one reason the properties of a substance are considered when selecting appropriate biodegradation methods.

What is the difference between biodegradability and persistence?

Biodegradability describes whether microorganisms can break down a substance. Persistence describes how long a substance remains in the environment. The concepts are connected, but they are not identical.

A substance that does not biodegrade well in standardized screening study may still biodegrade under other conditions. Scientists can use additional information, including environmental degradation half-lives and from more realistic lab studies and field studies, to understand how long a substance may remain in particular environmental compartments.

Persistence also does not by itself determine environmental risk. Scientists consider biodegradation and environmental fate together with exposure and potential effects on organisms to understand overall environmental safety.

What do you want us to remember about biodegradation testing?

Biodegradation testing is a well-established field of environmental science supported by a robust scientific framework, with many different methods at our disposal to assess the biodegradation potential of chemicals. Typically screening tests, stressed and conservative but with a long pedigree, serve as a good initial prediction of biodegradability, with a pass score of >60% accepted as the threshold for prediction of environmental biodegradability. This is well accepted by regulatory bodies around the world, including US (EPA) and Europe, which classify such materials at >60% pass as biodegradable- their confidence is based on multiple research papers both during and after the screening methods were introduced. But like many other science fields, biodegradability remains an active area of research, particularly as scientists continue to improve our understanding of more complex materials such as polymers, and how biodegradation occurs across different environmental systems. Hence, scientists are working to ensure how to tier studies, starting from a screening study. And many complex materials that might fail a screening study, can still be biodegradable in the environment, and be shown as such with more advanced and higher tier studies.

Importantly, biodegradability is one part of understanding environmental safety. Scientists bring this information together with environmental fate, exposure, and potential effects to build a comprehensive understanding of how a substance behaves in the environment and whether it can be used safely.