According to a study published in ACS’ Environmental Science & Technology, melamine sponges might emit over a trillion microplastic fibers every month worldwide.
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If you have ever cleaned white shoes or removed crayon marks from a wall, you likely appreciate the effectiveness of melamine sponges. These sponges can effortlessly erase stubborn stains and scuffs due to their unique abrasiveness, requiring no extra cleaning agents. However, as these "magic" sponges wear out, they release microplastic fibers.
Melamine foam is composed of a poly(melamine-formaldehyde) polymer, which forms a network of hard, plastic strands. This structure creates a soft, lightweight foam that is unexpectedly abrasive, making it an ideal material for highly effective scrubby sponges.
However, as the sponges wear away from use, the foam breaks down into smaller pieces that can release microplastic fibers, which wash into sewer systems. Once released into the environment, these fibers can be consumed by wildlife and enter the food chain. Researchers Yu Su, Baoshan Xing, Rong Ji, and colleagues aimed to see how a melamine sponge’s density and the roughness of the surface it scrubs affect the rate of foam breakdown, as well as calculate the number of microplastic fibers shed.
The team purchased several sponges from three popular brands and repeatedly rubbed them against textured metal surfaces, causing the foam to wear down. They found that sponges made from denser foam wore down more slowly and produced fewer microplastic fibers than less dense sponges. They determined that a single sponge releases approximately 6.5 million fibers per gram of worn-out sponge and assumed that all sponges sold, on average, are worn down by 10 %.
To estimate the number of fibers released per month, they looked at Amazon’s monthly sales for August 2023. Assuming consistent sales, the team calculated that 1.55 trillion fibers from melamine sponges could be released every month. However, this estimate only considers one online retailer, so the actual amount could be even higher.
To help minimize the emission of microplastic fibers, the researchers recommend that manufacturers create denser, tougher sponges that are more resistant to wear. Additionally, they suggest consumers opt for natural cleaning products that do not use plastics and recommend installing filtration systems to capture sloughed-off microplastic fibers either in homes or in wastewater treatment plants.
The National Natural Science Foundation of China and the Key-Area Research and Development Program of Guangdong Province funded the study.
Journal Reference:
Su, Y., et. al. (2024) Mechanochemical Formation of Poly(melamine-formaldehyde) Microplastic Fibers During Abrasion of Cleaning Sponges. Environmental Science & Technology. doi:10.1021/acs.est.4c00846