The kitchen sponge sheds microplastics – but you can help reduce the environmental problem yourself.
Økologisk NuA sponge that is likely located near your kitchen sink wears out every time you use it, and the wear does not disappear into thin air. If the sponge is made of plastic materials — as most scrubbing sponges are — it will release microplastics, which end up in the drain, then in the environment, and on agricultural fields. Researchers have now measured how much microplastic is actually shed by testing three types of sponges: two common ones containing 42% and 59% plastic respectively, and one marketed as organic, containing only 16% plastic. It should be noted that the sponge marketed as organic should not be confused with food products certified as organic. The biggest culprit in the study was a common yellow sponge with a blue surface and a black scrubbing layer from a European supermarket: it released an amount equivalent to 4.2 grams of microplastics per person per year. The second common sponge from the North American market released about 1.2 grams annually, while the one marketed as organic released 0.7 grams — roughly six times less than the typical European sponge. However, there is significant variation between households — some shed considerably more, others less. The difference is not due to the organic sponge wearing out less, but rather the proportion of plastic in the material. PET degrades more slowly The plastic content in the organic sponge tells two stories. On one hand, it is made from recycled PET, meaning no new plastic needs to be produced to make the sponge. On the other hand, PET degrades more slowly in nature than some other plastics, which are found in the conventional European sponge. The researchers supplemented their study with life cycle analyses of the sponges from raw material to waste, calculating their overall impact on ecosystems per 100 hours of dishwashing. The organic sponge had the lowest impact. However, the researchers emphasize that the goal was not to compare the sponges directly but to identify where in the sponge’s life cycle the environmental burden occurs. The figure for the North American sponge should be taken with caution: the researchers lacked data on water supply and waste management in the USA and had to use generic global figures, which assume open burning of waste — something the researchers note does not align with American practices. Water use has the greatest impact According to the researchers, microplastics are not the main problem when washing dishes by hand. Their life cycle analysis showed that between 85.7% and 96.8% of the damage to ecosystems comes from water consumption during washing. The plastic release from using the sponge accounts for less than 0.01%. “Water use overshadows all other impacts,” the researchers write in the study. This is due to both the production of drinking water and the treatment of wastewater afterward, which consumes energy and releases metals into the groundwater. The researchers assess that kitchen sponges are a minor to moderate source of microplastics in homes. For comparison, a plastic cutting board releases between 7.4 and 50.7 grams annually, and a German survey estimates that each German is responsible for about four kilograms of microplastics per year from 51 different sources, including car tires, artificial turf, waste management, and synthetic clothing fibers. End up on agricultural fields Although the figures are calculated in grams or a few kilos per person, the total becomes significant when everything is summed up. If every German household used the conventional European sponge, it would alone release about 355 tons of microplastics annually. Wastewater treatment plants capture about 90% of the microplastics, but they do not eliminate them — they end up in sewage sludge, of which 14% is spread on farmland as fertilizer. In the German calculation, this amounts to nearly 45 tons of microplastics on fields each year. The study does not address whether microplastics harm health, and this question remains open. Particles have been found in blood, placenta, and breast milk, but research cannot yet definitively say whether they make us sick. The EU’s food safety authority, EFSA, is expected to release its assessment in 2027. For the soil, the picture is clearer: a 25-year field experiment showed that microplastics from wastewater sludge remain in the soil for at least 22 years. The new study was published in the journal Environmental Advances.
The scrubbing sponge that is probably located by your kitchen sink wears down every time you use it, and the wear does not disappear into thin air. If the sponge is made of plastic materials — as most scrubbing sponges are — it will therefore release microplastics, which end up in the drain and later in the environment and on agricultural fields.
How much microplastic is actually worn off, has now been measured by researchers by testing three types of sponges: two common ones, which contained 42% and 59% plastic respectively, and one marketed as organic that contained only 16% plastic. It should be noted that the sponge marketed as organic should not be confused with food products that are certified organic.
The biggest culprit in the study was a common yellow sponge with a blue surface and a black scrubbing layer from a European supermarket: It released what corresponds to 4.2 grams of microplastics per year per person.
The second common sponge from the North American market released about 1.2 grams per year, while the one marketed as organic released 0.7 grams — about six times less than the typical European one. However, the variation between households is large — some released significantly more, others less.
The difference is not due to the organic sponge wearing less, but to how much of the material is plastic.
PET degrades more slowly
The plastic content in the organic sponge tells two stories. On one hand, it is made from recycled PET, which means no new plastic needs to be produced to make the sponge.
On the other hand, PET degrades more slowly in nature than some other types of plastic, which are also found in the conventional European sponge.
The researchers supplemented the study with life cycle analyses of the sponges from raw material to waste and calculated their overall impact on ecosystems per 100 hours of dishwashing. Here, the organic sponge ranked lowest. However, the researchers emphasize that the purpose was not to compare the sponges against each other, but to find out where in the sponge’s life cycle the burden occurs.
The figure for the North American sponge should be taken with particular caution: the researchers lacked data for both water supply and waste management in the USA and had to use generic global figures, which among other things assume open burning of waste — something the researchers themselves point out does not match American conditions.
Water consumption causes the greatest impact
According to the researchers, microplastics are not the main problem when washing dishes by hand.
Their life cycle analysis showed that between 85.7% and 96.8% of the damage to ecosystems comes from water use during washing. The plastic release from using the sponge itself accounts for less than 0.01%.
"Water consumption overshadows all other impacts," the researchers write in the study.
This is due to both the production of drinking water and the treatment of wastewater afterward, which consumes energy and releases metals into the groundwater.
The researchers assess that kitchen sponges are a minor to moderate source of microplastics in the home. For comparison, a plastic cutting board releases 7.4–50.7 grams per year, and a German survey estimates that each German is responsible for about four kilograms of microplastics annually from 51 different sources, including car tires, artificial turf, waste management, and synthetic clothing fibers.
Ends up on agricultural fields
Although the figures are calculated in grams or a few kilos per person, it still amounts to a different scale when everything is added up. If every single German household used the conventional European sponge, it would alone release about 355 tons of microplastics per year.
Wastewater treatment plants capture about 90% of the microplastics, but they do not disappear — they end up in sewage sludge, of which 14% is spread on farmland as fertilizer. In the German calculation, this amounts to nearly 45 tons of microplastics on fields annually.
The study does not address whether microplastics harm health, and that question remains open. Particles have been detected in blood, placenta, and breast milk, but research cannot yet say with certainty whether they make us sick, and the EU’s food safety agency EFSA is waiting until 2027 for its assessment. For the soil, the picture is clearer: A 25-year field experiment has shown that microplastics from wastewater sludge remain in the soil for at least 22 years.
The new study is published in the journal Environmental Advances.