The results show that kitchen sponges do shed measurable amounts of microplastics over time. However, the researchers found that the biggest environmental burden associated with hand washing dishes is not the plastic particles themselves. Instead, water use accounts for the vast majority of the overall impact.

Kitchen Sponges as a Source of Microplastics

Although kitchen sponges are used daily in millions of households, their role as a source of microplastics has received relatively little attention. The research team set out to measure how much plastic is released as sponges wear down during normal use and to evaluate the environmental consequences through a life cycle assessment (LCA).

To gather realistic data, the study combined laboratory testing with citizen science. Households in Germany and North America volunteered to use one of three sponge types as part of their regular dishwashing routines while documenting how the sponges were used.

Researchers weighed each sponge before and after use to determine how much material was lost over time. They also conducted controlled laboratory experiments using an automated testing system known as “SpongeBot,” which reproduces the mechanical stress that sponges experience during dishwashing.

How Much Microplastic Do Sponges Release?

The study found that every sponge tested lost material during use, resulting in the release of microplastics. Depending on the sponge type, annual emissions ranged from about 0.68 grams to 4.21 grams of microplastics per person.

Sponges made with lower amounts of plastic released significantly fewer particles than those with higher plastic content.

Citizen science played an important role in the project because participants used the sponges under real household conditions. This allowed researchers to capture realistic dishwashing habits and usage patterns, leading to more accurate estimates than laboratory testing alone could provide.

Water Consumption Has the Largest Environmental Impact

While the amount of microplastic released by an individual sponge may seem small, the totals become much larger when scaled up. The researchers estimated that if a particular sponge type were used in every German household, annual emissions could reach as much as 355 tonnes of microplastics.

Although wastewater treatment plants capture a large share of these particles, several tonnes could still enter rivers, lakes, oceans, and soils each year.

Even so, microplastics were not the primary driver of environmental damage in the study. The environmental assessment found that approximately 85 to 97 percent of the total impact of manual dishwashing comes from water consumption. Compared with water use, microplastic emissions contributed a much smaller share of overall ecosystem damage.

How Consumers Can Reduce Their Environmental Footprint

The researchers identified several practical steps consumers can take to lessen the environmental impact of washing dishes:

• Use less water while washing dishes, since this provides the greatest environmental benefit.
• Choose sponges with lower plastic content to reduce microplastic release.
• Keep sponges in use for longer periods, as extending their lifespan lowers overall resource consumption.

Research Team and Publication

The study involved researchers from the Institute of Organismic Biology (BIOB) at the University of Bonn, the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT, and Leiden University.

The findings were published in Environmental Advances in the paper From sink to sea: Microplastic release from kitchen sponges and potential environmental effects by Leandra Hamann, Christina Galafton, Peter T. Rühr, Alexander Blanke, and Nils Thonemann.