Plastic is now omnipresent also in our kitchens, for example, we think of the capsules for the dishwasher, which save us time and effort. Just insert one in the appropriate basket and the detergent does everything alone, without the need to measure dust or liquids. But, beyond the practicality, what happens to really the plastic contained in the capsules once dissolved in the water? Are you visible on the dishes? Do you disperse in the environment?
The answer is not as obvious as it might seem. Although the capsules are designed to dissolve without leaving obvious residues, some experts warn that the fate of plastic can be more complex than they imagine, with possible effects still unclear both on the dishes that we bring to the table and on the environment.
But let’s take a step back to better understand what type of plastic it is used in the capsules.
A “soluble” plastic, but really harmless?
The capsules contain a polymer called PVA (polyvinyl alcohol), designed to melt in contact with hot water, apparently without leaving visible residues.
The films are sufficiently resistant not to be broken if you touch with wet hands, but at the same time quite malleable to allow the detergent to “go out and do its job” in the dishwasher, explains Lauren Duffy, environmental toxicologist and senior scientist at the Environmental Working Group.
The plastic molecules that remain, once dissolved in the water, do not fall into the definition of microplastics, because they are liquid rather than solid. For this reason, most experts agree that the risk of toxicity deriving from the direct consumption of any residues on the dishes is minimal.
However, as Sherri Mason, chemistry and researcher points out at Gannon University:
To say that it dissolves simply means that it is not seen. The water still contains plastic molecules when it comes out of the dishwasher and heads towards the pipes, towards the nearest waste water treatment system.
What happens (or does not happen) in the treatment plants is therefore crucial to understand if there are reasons for concern. According to Duffy, most of the tests show that the plants have the right conditions to further decompose the polymer, avoiding accumulations in the environment or organisms.
In 2021, a Belgian study noted that the PVA degrades enough to be considered safe in 1-2 months, thanks also to the ability of the microbes present in the purifiers to absorb it and decompose it more easily than other plastics.
For these reasons, the dishwasher capsules are approved by the Safer Choice program of the United States’s environmental protection agency (EPA) and the Verified ENVironmental Working Group program, even if only the capsules containing dust receive certification, because the liquid ones can be accidentally ingested by children.
However, not all experts are of the same opinion. Charles Rolsky, executive director of the Shaw Institute, remember that:
Many studies suggest that the polymer can pass through the treatment of waste water without completely degrading. It all depends on temperatures, types of microbial communities and other environmental factors in the systems.
Varun Kelkar, environmental engineer, adds:
Standard tests take place in a very controlled environment, but this may not reflect some real conditions.
Rolsky and Kelkar estimate that polymer molecules frequently penetrate rivers and oceans, where their interactions with marine life and other contaminants are still unknown. As Rolsky explains:
There is a period of time during which the polymer has not been biodegraded enough, and this has an impact. It is as if plastic turned into something that we cannot even define.
And for human health?
According to the searches available, the hydrosoluble PVA has a minimal tendency to accumulate in human tissues. As Lauren Duffy of the Environmental Working Group explains: “Hydrosoluble compounds are less likely to accumulate in fatty tissues“.
An Italian study from 2022 analyzed the breast milk of 34 women looking for plastic contaminants: on 26 samples in which plastic was present, only 2% was pva. In addition, none of these particles resembled the PVA used in detergent capsules, most of the plastic found instead came from other daily use products, such as shopping bags and food containers.
However, there remains some uncertainty: Rolsky cites studies that suggest how low exposures to hydrosoluble pva can influence the growth of frogs and fish, highlighting a possible cumulative effect. Furthermore, even if the PVA is not toxic in itself, it could act as a carrier of other contaminants. Its chemical structure, however, makes the link with pesticides or heavy metals unlikely.
In summary, Rolsky and Kelkar warn:
In itself it is not a toxic material. But it spreads into the environment in large quantities. Even small quantities, acting as vectors, could have cumulative effects. It is necessary to study their impact on ecosystem and human health.
Until the research clarifies all the unknowns, the easiest solution to reduce the environmental impact remains to choose traditional powder or liquid detergents, possibly packaged in recyclable materials. An interesting alternative are then the “nude” pods, without plastic wrapping that offer the same practicality of traditional capsules without introducing polymers into the exhausts, thus further reducing the environmental impact.
It is not just a matter of convenience, it is a small gesture that helps to limit the production of plastic and to protect the environment.
Sources: Time /Polymers /EPA
