Imagine every person on Earth creating over 50 kilograms of plastic waste each year. Picture 32% of all plastic escaping into our environment—accumulating in our oceans, our soil, and even our air—while only 9% ever gets recycled 2 3 . This is the staggering reality of our plastic footprint, an environmental crisis unfolding in plain sight yet often remaining invisible to the untrained eye.
Plastic doesn't disappear—it transforms into microplastics smaller than 5 millimeters that now permeate every corner of our planet, from the deepest ocean trenches to the most remote polar ice 1 .
Researchers have developed a powerful tool called the Specific Area Under Band (SAUB) method that allows us to measure precisely how plastic degrades in the environment.
To understand how scientists track plastic degradation, we first need to talk about oxidation—the same process that causes iron to rust or an apple to turn brown. When plastic is exposed to environmental stresses like sunlight, heat, and physical abrasion, its molecular structure begins to change. Ultraviolet (UV) radiation from sunlight is particularly effective at breaking chemical bonds in plastic polymers, creating highly reactive molecules that then combine with oxygen from the air 1 .
This oxidation process forms carbonyl groups—specific arrangements of carbon and oxygen atoms that serve as chemical fingerprints of degradation. The more a plastic item degrades, the more carbonyl groups accumulate on its surface.
The carbonyl index (CI) acts as a "degradation thermometer" for plastics. For decades, scientists have used Fourier-Transform Infrared (FTIR) spectroscopy to detect these carbonyl groups by measuring how plastic samples absorb infrared light at specific wavelengths 4 .
Formation of carbonyl groups during plastic degradation
The scientific community knew it had a measurement problem. Different research papers reported carbonyl index values on completely different scales, with some methods producing CI values ranging from 0-1.5 while others reported values up to 20 for similar materials 4 . This lack of standardization created chaos in the field.
To understand how the SAUB method works in practice, let's examine a pivotal experiment detailed in the research literature. The Polymateria team designed a comprehensive study to compare traditional CI calculation methods against their new SAUB approach, testing both polyethylene (PE) and polypropylene (PP)—the two most common commercial plastics that together account for nearly half of all plastic production 3 4 .
Researchers gathered samples of both virgin (new) and artificially weathered plastics through accelerated aging that simulated years of environmental exposure.
Using Attenuated Total Reflection Fourier-Transform Infrared (ATR-FTIR) spectroscopy, which analyzes the plastic surface with minimal sample preparation.
Simultaneous analysis using both traditional peak-height measurements and the new SAUB approach for direct comparison.
Results compared across different sample types, degradation stages, and plastic formulations to assess consistency and accuracy 4 .
| Sample Type | Degradation Stage | Traditional CI Method | SAUB Method |
|---|---|---|---|
| Polyethylene (PE) | Early degradation | 0.15 | 0.18 |
| Polyethylene (PE) | Moderate degradation | 0.42 | 0.51 |
| Polyethylene (PE) | Advanced degradation | 0.85 | 0.92 |
| Polypropylene (PP) | Early degradation | 0.18 | 0.21 |
| Polypropylene (PP) | Moderate degradation | 0.48 | 0.49 |
| Polypropylene (PP) | Advanced degradation | 0.91 | 0.95 |
The true test of any scientific method lies in its application to real-world problems. Recently, an international team of researchers applied the SAUB method to investigate microplastic degradation in the Northwest Pacific Ocean and Tokyo Bay 1 . Their findings have profound implications for our understanding of plastic pollution.
Smaller microplastics showed significantly higher carbonyl indices than their larger counterparts. For polyethylene, average CI measured 0.70 for large microplastics (>350 μm) but jumped to 2.58 for small microplastics (50-350 μm)—nearly four times higher 1 .
In Tokyo Bay, PE microplastics showed significantly higher CI values than those from open ocean sites, suggesting that environmental context matters—the unique combination of pollution sources and conditions creates distinct degradation pathways 1 .
Understanding plastic degradation requires sophisticated tools and methodologies. Here's a look at the essential equipment and approaches that scientists use to track plastic transformation in the environment:
The workhorse instrument for carbonyl index measurements using infrared light to identify chemical bonds.
Simulates years of environmental exposure through controlled UV radiation, temperature, and moisture.
Carefully characterized plastic samples with known compositions serving as benchmarks for comparison.
Tracks the fate of carbon atoms from original plastic as they transform into various degradation products. This method has revealed that approximately 17% of plastic carbon is released as volatile compounds during degradation .
Standardized procedures that simulate long-term environmental degradation in compressed timeframe, allowing prediction of plastic behavior over years or decades.
The development of the SAUB method represents more than just a technical improvement in laboratory techniques—it embodies a crucial shift in how we approach complex environmental problems. By creating a standardized, reliable way to measure plastic degradation, scientists have given us a powerful tool to develop real solutions, from designing truly biodegradable plastics to understanding the environmental lifetime of plastic products.
As we move forward, this ability to accurately track plastic's transformation in our environment will be crucial for evaluating new materials, guiding policy decisions, and ultimately turning the tide on plastic pollution. The next time you see a piece of weathered plastic on the beach, remember that scientists now have ways to read its history—and this knowledge may be key to preventing its legacy from enduring for centuries.
The careful work of standardizing how we measure degradation reminds us that before we can solve an environmental crisis, we must first learn to see it clearly—and the SAUB method offers us precisely that clarity.