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Comment by trebor | Hacker News Reader

Ironically, the summary isn't as good as the "Key Messages" section at the bottom:

> * Professional dishwasher rinse aid causes cellular cytotoxicity and directly impaired barrier integrity of gut epithelial cells by damaging TJ and AJ expressions in daily exposed concentrations. > * The underlying mechanisms of epithelial barrier disruption in response to rinse aid were cell death in 1:10,000 dilutions and epithelial barrier opening in 1:40,000 dilutions. > * The alcohol ethoxylates, an ingredient of the rinse aid that remains on washed dishware, caused the gut epithelial inflammation and barrier damage.

It appears to be the rinse aid when used in professional dishwashers utilized in restaurants, etc, due to high concentration of the rinse aid contaminating the "clean" dishes.

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Importantly, when they tested a household dishwasher, they didn't find the same issues:

> In contrast, the residual substances on the cups washed in a household dishwasher with detergent B were not present at sufficiently high concentrations to exert cytotoxicity and impair the epithelial barrier function (see Fig E9).

Also, they've only tested one professional dishwasher and one household dishwasher using one specific formulation of rinse aid.

There's enough here to indicate a need for further investigation, but not enough data to come to any overall conclusions about commercial or household dishwasher safety in general.

They call for further study at the end, acknowledging that their data was all /in vivo/ in a lab, and not direct data in humans. Thus, while they claim to have demonstrated a mechanism, they make no claims that it works the same way in people.

"In vivo" means in a living body. "In vitro" means in the lab/petri dish.

> They call for further study at the end

Tangent: most papers seem to do that… which confuses me. It feels like it’s basically saying to discard everything the paper talked about because to be actually sure you’d need to investigate more than they did.

Is it a pro forma formula or does it really mean what I understand it to?

Generally, answering questions will raise new ones. It is very unlikely for a single paper to be the end of a line of research. Sometimes the new questions are quite fundamental (like here), sometimes the new questions are details, and sometimes the further research is "try this same method on this other known big problem".

Besides the inherent fractal nature of how science works, there is also an incentive. Being a scientist in a solved field is not very smart. Or even more cynically the 'further work' section says 'please pay me to do these things next'.

But I think the cynical view is not as important here. Research tends to be strictly limited in time, and for good reason. During the research you will probably find new directions, and also get insight into what old questions are interesting, or what new methods matter. All of these are great cause to include a further work section.

If you use a rinse aid in your dishwasher I bet you’d find harmful results.

Home detergent does contain AES (sulfates) but it gets rinsed pretty well. However if you use rinse aid, the rinse water itself has surfactants (AES, more sulfates), which will remain on the dishware- that’s the whole point actually, so the water beads off.

One of the most popular brands in the US, Jet Dry, has the ethoxylated alcohol mentioned in the article:

http://www.rbnainfo.com/MSDS/CA/FINISH%20-%20JET-DRY%20Rinse...

The rinse aid prevents beading, actually. Beading is what leaves the spots.

Yes I had it backwards. It’s the old “add soap to water to break the surface tension” kids science experiment: https://youtu.be/ho0o7H6dXSU

Yeah in industry they are often called sanitizers because the purpose and mechanism are fundamentally different from the home ones people are familiar with. Or as a common chef quip: "the dishwasher is the guy running it, the machine is a sanitizer."

They are notoriously bad at removing food residue, which must be sprayed or scraped off before running. Anything more than trace is cooked onto the dishes. They're really good at removing thin layers of grease quickly, and sanitizing. Doesn't surprise me at all that they don't do a final rinse; handling stuff right out of them leaves a distinct feeling on your fingers, like the opposite of bleach kinda. You have more friction than you should until they fully dry, it's very noticeable.

you seem to be in expert on these matters, on an experiential level?

Started working as a dishwasher as a teenager, ended up spending a couple decades cooking professionally eventually at a pretty high level. Did something else for a while, then got back into it for another few years before learning to code and ending up here.

I have sensitive taste buds and worked for an industrial kitchen with a Hobart washer:

1. Rinse plates before putting them in crates

2. Slide the crates into the washing machine.

3. Close the machine to get it to perform a 3-stage cycle over 2 or 3 minutes: soap, sanitizer (usually some ammonium solution like in sanitizing tablets), then rinse.

I was able to taste bitterness after the rinse cycles and we were never in a rush, so I had the habit of re-rinsing the plates afterwards.

In restaurants I notice soap in my water or on the plate every now and then. It seems like most people don’t mind or notice. If you don’t feel the texture change or taste the bitterness of soap, you can see it by observing pearlescent colors on the surface of your drink.

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