I tried googling an answer to this one, but this is one of those times when Google just didn't provide an answer. It says that trees are good at removing contamination from soil and that harvested sap is prone to molding if not handled correctly and occasional warnings about DIY maple syrup production, but nothing on whether undesirable minerals go from the groundwater into the sap of the tree.

Any researched backed information would be appreciated.

  • For what purposes will you be using the tree sap? Commented Oct 27, 2023 at 10:32
  • Maple sap. Maybe I should have been more specific and I'll put that in the question. The purpose is back yard home made maple syrup. Most of the concerns with maple syrup are very easy to look up. Don't over-tap the trees, and warnings about mold or bacterial contamination for home production. But the first question, In an area where the ground water isn't safe for drinking, does that affect the maple sap? That has me stumped, and so far, stumped my friend google too.
    – userLTK
    Commented Oct 27, 2023 at 10:36
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    I'm no expert on ground water contamination, but I would expect that it depends on what exactly is making the groundwater unsafe. What kind of contamination are we talking about?
    – THelper
    Commented Oct 27, 2023 at 13:27
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    I made maple syrup a couple years, simple and easy. No sign of any of the problems you found on the net. I made it before the net , so did not know any of problems created by the net. Commented Oct 27, 2023 at 15:27
  • @THelper It's south Jersey not far from Philly. I don't think it's anything really toxic, but I can try to find out a bit more. It seems to me there are a couple of possibilities. Either trees store toxins in their sap, or they don't. Trees are good at picking up toxins from the soil, but that doesn't mean the toxins concentrate in their sap. It seems like there should be an answer out there, but I've had no luck finding one. You're also right that the type of toxin might matter, but I think any research on this would address that.
    – userLTK
    Commented Oct 27, 2023 at 19:15

2 Answers 2


The problem is the general word "toxins" covers just too much.

Say the soil in an area is so rich in arsenic that the groundwater is contaminated with it and you shouldn't drink it. That's entirely different from an aquifer having bacterial contamination like e. coli in it. And both of them are different from having some leaking industrial site putting carcinogens into the water. You aren't even sure if the tree is taking up the water in question - a river or pond can be contaminated with no impact on a tree 100 feet away from it. (I do feel that "undesirable minerals" is totally not a thing.) It would help if you knew what made the groundwater undrinkable in the area you're considering.

Setting aside "does the tree take up the toxin or not, and if so does it end up in the sap?" as unanswerable because it will vary toxin by toxin, you can still draw some conclusions. Two things are likely to help you relax about your maple syrup: the boiling, and the dose. Boiling will kill bacteria and boil off "light" components such as some hydrocarbons. And you consume maybe a litre of maple syrup a year, right? Or two if you're crazy for it? While you take in more water than that every day. So the threshold for "you shouldn't drink this water it will poison you" is at a very very low level.

If the contamination is not an instant poison like arsenic, but more a "over the years it could really add up" thing like radon, I would trust the syrup. If the issue is bacterial, I would trust the syrup. Beyond that I can't say without knowing what contaminants are worrying you.

  • 1
    For the record, radon doesn't build up. It decays quicky. That's why, even in poorly ventilated basements where radon is a problem, radon inspectors don't even bother wearing protective gear. It takes years for radon toxicity to happen. I also find it hard to believe that this subject has never been studied. There has to be an answer out there.
    – userLTK
    Commented Oct 30, 2023 at 7:37
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    Not that it could build up in the soil/atmosphere, but in you. Radon is indeed only a problem if you live in the house for years, not on a brief visit. So if you drank some maple syrup with radon in it, no big deal. Commented Oct 30, 2023 at 10:32
  • For chemical, and in particular inorganic pollutants, also the biochemistry of the tree matters - it may mean it's still safe, but some plants accumulate certain chemicals (e.g. cacao trees are quite "good" at extracting cadmium from the soil) Commented Apr 6 at 2:29

I believe most experts show that when dirty ground water is filtered through the roots and ecosystem underground like microorganisms and bacteria that specialize in recycling waste and filtering out the bad and turning into good for the roots they do such a good job of filtering that what the tree sucks back up into the tree is clean, thus your syrup is clean, you tube has some good content on how this works.

  • 3
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    – Community Bot
    Commented Feb 11 at 6:20
  • If you've seen YouTube videos on this, please post some. I did check YouTube before asking here. I found nothing conclusive. Ultimately there are three possibilities. 1) Tree sap is safe, even where the ground water is polluted. 2) tree sap is about the same toxicity as the ground water - small amounts might be OK, or 3) Tree sap concentrates the toxins from the ground water and should be avoided, especially when you consider that tree sap is usually boiled down so you get a concentrated amount when you make syrup. One of these 3 things is true, but I've yet to determine which.
    – userLTK
    Commented Mar 24 at 3:39

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