Assessing Extent of Degradation and the Potential Effects on the Quantification of Microplastics in the Environment

Plastic pollution is a global crisis, as waste in the environment breaks down into tiny particles called microplastics. Over time, sun exposure and weather change these plastics both physically and chemically. While scientists usually study this using surface-scanning tools, these methods often struggle with very small or dirty particles.

This research uses a technique called pyrolysis (heat-based breakdown) to study how three common plastics, polypropylene (PP), polyethylene (HDPE), and polystyrene (PS), change as they age.

A major discovery of this work is that current methods for measuring how much plastic is in a sample can be inaccurate. Most labs use "virgin" (new) plastic to calibrate their machines. However, this study found that as plastic weathers, the chemical "markers" we use to identify them actually start to disappear. If we don't account for this "signal loss," we might significantly underestimate the amount of pollution in our oceans and soils. For example, some weathered plastics showed a signal drop of up to 41%, meaning nearly half the plastic could go undetected.

To fix this, the research identified new "oxidation markers" chemical fingerprints that only appear after the plastic has been damaged by the sun. By tracking these markers, we developed a mathematical model that can estimate how "old" or degraded a piece of plastic is, even if we don't know how long it has been in the environment. This model was successfully tested on real-world samples collected from beaches in Hong Kong and Australia.

Ultimately, this project provides a new "toolkit" for scientists. By using heat to unlock the chemical history of a particle, we can more accurately measure plastic pollution and better understand its long-term impact on our planet. This is a vital step toward better environmental regulations and cleaner ecosystems.

Research Outputs

De-la-Torre, G.E., Dioses-Salinas, D.C., Severini, M.D.F., López, A.D.F., Dobaradaran, S., Toapanta, T.Y.A. and Okoffo, E.D., 2025. Aims of the analysis and the choices of analytical methods. In Analysis of Microplastics and Nanoplastics (pp. 63-77). Elsevier.

Muñoz-Perez, J.P., Lewbart, G.A., Toapanta, T., Chadwick, H., Okoffo, E.D., Alarcon-Ruales, D., Zurita-Arthos, L., Jones, J.S., Cisneros, F., Moreira-Mendieta, A. and Vintimilla-Palacios, C., 2024. Plastic pollution and health metrics in wild juvenile green sea turtles (Chelonia mydas) from two Ecuadorian national parks: Galápagos and Machalilla. Frontiers in Amphibian and Reptile Science, 2, p.1439512.

Burrows, S., Colwell, J., Costanzo, S., Kaserzon, S., Okoffo, E., Ribeiro, F., O'Brien, S., Toapanta, T., Rauert, C., Thomas, K.V. and Galloway, T., 2024. UV sources and plastic composition influence microplastic surface degradation: Implications for plastic weathering studies. Journal of Hazardous Materials Advances, 14, p.100428.

De-la-Torre, G.E., Santillán, L., Dioses-Salinas, D.C., Yenney, E., Toapanta, T., Okoffo, E.D., Kannan, G., Madadi, R. and Dobaradaran, S., 2024. Assessing the current state of plastic pollution research in Antarctica: knowledge gaps and recommendations. Chemosphere, 355, p.141870.

Burrows, S.D., Ribeiro, F., O’brien, S., Okoffo, E., Toapanta, T., Charlton, N., Kaserzon, S., Lin, C.Y., Tang, C., Rauert, C. and Wang, X., 2022. The message on the bottle: Rethinking plastic labelling to better encourage sustainable use. Environmental Science & Policy, 132, pp.109-118.

Okoffo, E.D., O'Brien, S., O'Brien, J.W., Tscharke, B.J., Rauert, C., Rødland, E.S., Ribeiro, F., Burrows, S.D., Toapanta, T., Mueller, J.F. and Thomas, K.V., 2022. Does size matter? Quantification of plastics associated with size fractionated biosolids. Science of The Total Environment, 811, p.152382.

Okoffo, E.D., Donner, E., McGrath, S.P., Tscharke, B.J., O'Brien, J.W., O'Brien, S., Ribeiro, F., Burrows, S.D., Toapanta, T., Rauert, C. and Samanipour, S., 2021. Plastics in biosolids from 1950 to 2016: A function of global plastic production and consumption. Water Research, 201, p.117367.

Toapanta, T., Okoffo, E.D., Ede, S., O'Brien, S., Burrows, S.D., Ribeiro, F., Gallen, M., Colwell, J., Whittaker, A.K., Kaserzon, S. and Thomas, K.V., 2021. Influence of surface oxidation on the quantification of polypropylene microplastics by pyrolysis gas chromatography mass spectrometry. Science of The Total Environment, 796, p.148835.

O'Brien, S., Okoffo, E.D., O'Brien, J.W., Ribeiro, F., Wang, X., Wright, S.L., Samanipour, S., Rauert, C., Toapanta, T.Y.A., Albarracin, R. and Thomas, K.V., 2020. Airborne emissions of microplastic fibres from domestic laundry dryers. Science of the Total Environment, 747, p.141175.

Conference Abstracts

Toapanta, T., Okoffo, E.D., O’Brien, S., Tariq, A., Fenti, A., Burrows, S., Gallen, M., Ede, S., Colwell, J., Whittaker, A., Kaserzon, S. & Thomas, K.V. Weathering indices for polypropylene, polyethylene, and polystyrene microplastics by Pyrolysis Gas Chromatography Mass Spectrometry, 7th International Marine Conservation Congress (IMCC7), South Africa, 13-18 October 2024.

Toapanta, T., Okoffo, E.D., O’Brien, S., Burrows, S., Ribeiro, F., Gallen, M., Ede, S., Colwell, J., Whittaker, A., Thomas, K.V. & Kaserzon, S. Weathering indices for polypropylene, polyethylene, and polystyrene microplastic samples by Pyrolysis Gas Chromatography Mass Spectrometry, SETAC Australasia 2023, Townsville, Australia, 7-11 August 2023.

Toapanta, T., Okoffo, E.D., O’Brien, S., Burrows, S., Ribeiro, F., Gallen, M., Ede, S., Colwell, J., Whittaker, A., Thomas, K.V., Kaserzon, S. Chemical characterisation of degraded polypropylene, polyethylene and polystyrene microplastic samples, 58^th Annual Conference of the Australian Marine Sciences Association, Cairns, Australia, 7-11 August 2022.

Toapanta, T., Okoffo, E., Ede, S., O’Brien, S., Burrows, S.D., Ribeiro, F., Gallen, M., Colwell, J., Whittaker, A.K., Kaserzon, S., Thomas, K.V. Quantification effects by pyrolysis gas chromatography mass spectrometry after photooxidation on the surface of polypropylene microplastics, SETAC-AU Conference 2021, Melbourne, Australia, 30 August – 2 September 2021.

Toapanta, T., Okoffo, E. D., O’Brien, S., Burrows, S., Ribeiro, F., Gallen, M., Ede, S., Colwell, J., Whittaker, A., Thomas, K. V., Kaserzon, S. Influence of simulated weathering on the quantification of microplastic polypropylene by Pyrolysis Gas Chromatography Mass Spectrometry. SETAC Europe, Online, 3-6 May, 2021.

Toapanta, T., Okoffo, E., Ede, S., O’Brien, S., Burrows, S. D., Ribeiro, F., Gallen, M., Colwell, J., Whittaker, A. K., Kaserzon, S., Thomas, K. V. Quantification effects by pyrolysis gas chromatography mass spectrometry after photooxidation on the Surface of polypropylene microplastics. SETAC Australasia, Melbourne, Australia, 30 August – 2 September 2021.

Toapanta, T., Okoffo, E., O’Brien, S., Burrows, S., Ribeiro, F., Gallen, M., Ede, S., Colwell, J., Whittaker, A., Thomas, K., Kaserzon, S. Signal decrease of microplastic polypropylene due to simulated weathering during quantification analysis with Pyrolysis Gas Chromatography Mass Spectrometry, EMCON, Virtual, USA, 13-14 September 2021.