Researchers find potential risks to the gut from rinse agents in dishwashers

It is assumed that defective epithelial barriers "play a role in triggering the onset of two billion chronic illnesses."
Deena Theresa
A dishwasher.
A dishwasher.

hsyncoban/iStock 

In an alarming new study, researchers at the Swiss Institute of Allergy and Asthma Research (SIAF), an associated institute of the University of Zurich, revealed that dishwashers, which revolutionized efficient cleaning and saving time, come armed with risks.

A specific ingredient found in commercial rinse agents has a "toxic effect" on the gastrointestinal tract, a press release said.

The epithelial barrier in the gut is associated with multiple illnesses

Cezmi Akdis, UZH professor of experimental allergology and immunology and the director of SIAF, noticed that in many dishwasher appliances, there's no additional wash cycle that removes the remaining rinse agent. Now in a commercial dishwasher, hot water and detergent circulate for around 60 seconds at high pressure. After which, a 60-second washing and drying cycle takes place in which water and the aforementioned rinse agent are applied. 

"This means that potentially toxic substances remain on the dishes, where they then dry in place," Akdis said. And when the dishes are reused, this dried chemical residue ends up in the gut.

This led the team to inspect the effects of commercial-grade detergents and rinse agents on the epithelial barrier in the gut. Usually, when there's a defect in this barrier, it is associated with conditions such as food allergies, gastritis, diabetes, obesity, cirrhosis of the liver, rheumatoid arthritis, multiple sclerosis, autism spectrum disorders, chronic depression, Alzheimer's disease, said the release.

"We assume that defective epithelial barriers play a role in triggering the onset of two billion chronic illnesses," said Akdis. 

Alcohol ethoxylates found as the culprit

For their study, the researchers used human intestinal organoids and intestinal cells on microchips. The former is used to form a 3D clump of cells which is very similar to the intestinal epithelium in humans. Biomolecular methods were used to examine the effect that the detergents had on these cells. 

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The research team found that high doses of these rinse agents damaged the intestinal epithelial cells. When explored further, it was found that one specific component of the rinse agent - alcohol ethoxylates - was responsible for this. 

According to Akdis, these findings have significant implications for public health. "The effect that we found could mark the beginning of the destruction of the gut's epithelial layer and trigger the onset of many chronic diseases," Akdis said. "It is important to inform the public about this risk since alcohol ethoxylates seem to be commonly used in commercial dishwashers," he added.

The study was published in The Journal of Allergy and Clinical Immunology on December 1.

Study Abstract:

Background: The increased prevalence of many chronic inflammatory diseases linked to gut epithelial barrier leakiness has prompted us to investigate the role of extensive use of dishwasher detergents, among other factors.

Objective: We sought to investigate the effects of professional and household dishwashers and rinse agents on cytotoxicity, barrier function, transcriptome, and protein expression in gastrointestinal epithelial cells.

Methods: We sought to investigate the effects of professional and household dishwashers and rinse agents on cytotoxicity, barrier function, transcriptome, and protein expression in gastrointestinal epithelial cells. Enterocytic liquid-liquid interfaces were established on permeable supports, and direct cellular cytotoxicity, transepithelial electrical resistance, paracellular flux, immunofluorescence staining, RNA-sequencing transcriptome, and targeted proteomics were performed.

Results: The observed detergent toxicity was attributed to exposure to rinse aid in a dose-dependent manner up to 1:20,000 v/v dilution. A disrupted epithelial barrier, particularly by rinse aid, was observed in liquid-liquid interface cultures, organoids, and gut-on-a-chip, demonstrating decreased transepithelial electrical resistance, increased paracellular flux, and irregular and heterogeneous tight junction immunostaining. When individual components of the rinse aid were investigated separately, alcohol ethoxylates elicited a strong toxic and barrier-damaging effect. RNA-sequencing transcriptome and proteomics data revealed upregulation in cell death, signaling and communication, development, metabolism, proliferation, and immune and inflammatory responses of epithelial cells. Interestingly, detergent residue from professional dishwashers demonstrated the remnant of a significant amount of cytotoxic and epithelial barrier–damaging rinse aid remaining on washed and ready-to-use dishware.

Conclusions: The expression of genes involved in cell survival, epithelial barrier, cytokine signaling, and metabolism was altered by rinse aid in concentrations used in professional dishwashers. The alcohol ethoxylates present in the rinse aid were identified as the culprit component causing the epithelial inflammation and barrier damage.