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We live in a rural area and our dish water runs out to a field. There must have been few tomato seeds in the water. We now have about 4 volunteer plants producing fruit.

Is it safe to eat tomatoes that have been watered with dish water?

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  • It does encourage the use of bio-degradable soap.
    – Boba Fit
    Commented Apr 17, 2023 at 21:00

3 Answers 3

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It is perfectly safe. In fact it is also legal to use gray water to water your plants. Some houses are designed to do this. Gray water is water from kitchen and laundry and in some cases also from showers.

We are in a rural area, and have a septic tank (which takes sewage as well). The water from that is used to water everything that is a bush or tree. We dont use it to water things like carrots, lettuces etc. This is purely to avoid splashes.

The plant will sort of filter and process that water for you.

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The University of Florida Institute of Food and Agricultural Sciences website includes this:

  1. Is reclaimed water safe for irrigating my vegetable garden?

The Florida Department of Environmental Protection states that reclaimed water should NOT be directly applied to the surfaces of vegetables or other edible crops that are not peeled, cooked, or thermally processed before being consumed. This statement essentially means that as long as you peel or cook your vegetables, they may be safely consumed after being grown with reclaimed irrigation water. The statement also means that indirect application methods, such as ridge or furrow irrigation, drip irrigation or a subsurface distribution system, which preclude direct contact, are allowed for edible crops that are not peeled, skinned, cooked, or thermally processed before consumption. See Figure 2 for an example of drip irrigation in which irrigation water does not contact plant surfaces.

So as Rohit's answer suggests, the plant itself using dishwater looks to be quite safe.

The concern hinted at by the UF answer (reclaimed versus greywater [and whether sink water is grey or black] sounds itself like a complex topic) would be that the tomato itself may have likewise been exposed to the continuing dishwater discharge, which would suggest the tomato skin could have soap on (or bonded into?) it.

Not knowledgeable on the subject myself, but while some remnant of the initial cells of the plant seed do seem to perhaps move upward in the mitosis of the apical meristem... could imagine that so many splits would leave very little residue from any contamination from the earlier days when it was at ground level to make it to the branches and subsequent flowers->tomatoes.

So then the question is how much the dish water can reach up to the level where the tomatoes started to form/continues to grow? Does the water get high in the field when it drains (I wouldn't have thought so, though it's dependent on where the plants are compared to the outlet, and how saturated your ground has been)? And does it splash (again the relationship to the initial outlet is likely key, in addition to terrain and release rate)?

Of course, you also have to consider what the chemicals are... looks like from the US CDC says:

Washing fruits and vegetables with soap, detergent, or commercial produce wash is not recommended. Do not use bleach solutions or other disinfecting products on fruits and vegetables.

And does the discharge also get things like laundry detergent and bleach?

If I were the one choosing, practically, I think I (and quite a few others) might feel safe to eat the tomatoes if I were convinced the water wasn't likely directly getting on the tomatoes. And I'd imagine that a very small amount of weak concentration dish detergent may not be the end of the world (I've certainly known people who don't rinse dishes after hand-washing with soap after all!). I would certainly wash the tomatoes of course at the very least. But in the end, you have to decide how comfortable you feel with/how risky you think it may be, which will change on a case-by-case basis. It doesn't seem there's an absolutely sweeping yes or no answer possible.

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Microbes can be transmitted to the tomato fruit from leaves, and can even grow within the plant.

So cook the tomatoes and wash your hands.

There is lots more research done on this.

Articles I looked at are:

“Movement of Salmonella serovar Typhimurium and E. coli O157:H7 to Ripe Tomato Fruit Following Various Routes of Contamination”

From

https://pubmed.ncbi.nlm.nih.gov/27682118/

And also

“Fate of various Salmonella enterica and enterohemorrhagic Escherichia coli cells attached to alfalfa, fenugreek, lettuce, and tomato seeds during germination”

From

https://www.sciencedirect.com/science/article/abs/pii/S0956713518300173

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