This Month’s FWW – Wood Toxicity – Discussion Please
What I am particularly focused on is the question about extractives with walnut. I have used lots of it in cutting boards and bowls usually in combination with other woods. The article states that for cutting boards a drying oil should be used as a barrier, not mineral oil. For all of my work I have used mineral oil with wax with no issues. Like most of us, I also add bloodwood, padauk, etc. for color accents.
I can see the concern with some of these woods if they are going to be immersed in cold or hot liquids when using spoons, but for cutting boards and bowls that will be hand washed and dried? Here’s where I hope we can have a constructive conversation – when it comes to cutting boards and bowls, is the concern getting overstated, unless there is a person or customer that might have a particular sensitivity? Appreciate all of your thoughts. Have a good woodworking day!
Replies
Once upon a time I made hundreds if not thousands of sandwich boards and butter trays. It was a gift catalog thing and kept the lights on. Finished them with nothing more than white ( food grade) mineral oil. I still have examples of those in use at my home 40 years later and with an occasional reup of oil they have held up all this time. Mineral oil is what I use on wooden utensils as well. I take no special care of things like wooden spoons, they are simply tools for cooking and have a hard life and look like they have. I didnt make my spoons but somehow I do have alot of wooden spoons and I don't remember ever buying a single one. Only once did I ever make some wooden salad servers. I make something to give away at Christmas and one year i had a broken arm. It was the only thing i could think of that i could do one handed and left handed at that. On cutting boards ,salad bowls and counter tops I use bees wax and white mineral oil. The insides of salad bowls are self oiling - olive oil ,vegetable oil and reoiled dailey.I have made my own beeswax and oil in the past but I just purchase it already made.
Mineral oil is odorless and tasteless. I think that is important when it's something that comes in contact with food. It's approved and considered food safe. Nut oils concern me because of people with nut allergies. I don't have that problem but have decided to believe people who claim they do.
I once came upon a thread with people talking about this very subject and people claiming that they have felt effected by what had been applied to things like cutting boards and counter tops. Several people claiming that tung oil was fine to use and then others who have known peanut allergies saying that they are reactive to tung oil as well. The conversation got very heated with people claiming that that was impossible, essentially saying that the people with allergic reactions were either lying or it was in their heads!
Things like linseed oil stink ,any other oil that I can smell I can't think of a reason why I would use it on something that comes in contact with food even if the smell eventually dissipates. I couldn't tell if it had dissipated probably..at this point linseed oil and solvents are part of my DNA!
Are the people saying that you should use a drying oil saying this for water resistance? You slice through any finish you use. A straight up oil you just reapply when needed, low maintenance.
I made some cutting boards, a Chrismas thing and the kids got them, relatives, a couple of friends. I have one. They were pretty nice ,decorative you might say and when I go to a house where one of these things ended up they have set them up somewhere as a display! Maybe they do use them to ste some cheese or nuts on them on occasion. I intended for them to be used! They're supposed to have knife marks and maybe some stains, maybe a burn mark or two ,get dumped in the sink after dinner! They're a cutting board!
This may help you
https://www.christofix.com/is-walnut-wood-toxic/
Toxicity is as much a matter of quantity/exposure as it is of the substance, for a meaningful discussion it would be interesting to quantify the amount of toxic substance that will cause health problems.
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Well that would require studies. Maybe studies have been done by ,or rather, for industries or unions maybe. I would think that in countries like Denmark or Germany where they have large woodworking industries and universal health care that you might find that there have been government funded studies related to wood exposure. Its worth it for them to know, they pay the bill!
Any Einstein awarded Pasteur Institute researchers frequenting this site? Speak up!
Growing up there was no dust collection or air infiltration in small shops, certainly not in home shops. The machines you bought had no port to hook up to and if they did,like for example my radial arm saw they didnt work anyway or a dust bag that collected very little of the dust. My high-school had a beautiful shop but dust collection was a broom and dust pan. The only place you might find dust collection back then was at some industrial shop running a "48 Greenlee planer and I don't think it had anything to do with workers health as much as that they couldn't find a dust pan big enough to handle all those chips!
You never heard of woodworkers having health problems associated with exposure to wood. Everybody smoked of course so that would have camouflaged any lung problems. Other industries you did but not woodworkers. Wood finishers were like sacrificial lambs in industrial situations! Denial was popular back then. I remember when the coal miners were trying to get some support from the industry to do something about black lung disease and the companies fought it and denied its existence for years! Men were men --if you were hurt or ill you could whimper a little but you never cried! So possibly people may have had problems but just kept quiet. My grandfather started in the steel mill when he was 11 years old and was present when Andrew Carnegie himself reached into his own pocket and gave a worker ,who had lost an arm ,a $50 gold piece. 70 years later my grandfather was still impressed by the gesture!
Anyway it's a difficult subject to talk about without some actual science to back it up! Too many things that you read on the internet are coming from some Billy Bob the woodworker and not from some medical journal. We can all talk about our own experiences and since we are all made a little different we will all have different stories. I find some woods to be particularly irritating to work with but I've never had an allergic reaction or any health problem that i can associate to any kind of wood myself. I do know a guy that ended up killing himself with redwood dust though. If you saw what he was doing and the accumulated dust in his shop its no wonder that that was the result. I recently acquired some of the lumber from his shop. It all had this 3/8" layer of compacted superfine saw dust and the dust on the bottom could have been 30 years old!
I did a deep dive into Walnut evidence a couple of years ago.
There is good evidence that consuming shavings of Julgans Nigra can induce laminitis in equine species, though the exact mechanism is uncertain. Although studies are small in scale, the effect has been reproduced and is a useful model for studying laminitis as a condition.
Walnut extracts and fresh walnut shavings can also slightly suppress the growth of other plant species. Juglone, an alkaloid which can be extracted from the wood is quite toxic to plants, but oxidises in soil too quickly for this to be the plausible mechanism. The reason for this activity remain uncertain, but it is very small in nature.
Allergies to specific species may occur, and allergy, especially to unusual allergies can be quite idiosyncratic, and there are several different mechanisms.
IgE mediated immediate allergy (Type 1) (such as seen in peanut allergy) is thought to be related in many cases to exposure to the allergen through routes other than oral - the immune system learns that things taken by mouth are food and things that arrive by other routes are foreign and therefore subject to a reaction. This is why it is important to feed peanut to children early - avoiding doing so is a major cause of peanut allergy as there is so much peanut in the environment it is hard to avoid getting it on your skin.
Allergies mediated by other immunoglobulins (usually IgG and IgM) can be more subtle and produce quite unusual effects which may last much longer than the 'classic' anaphylaxis, and it can be difficult to pin down a cause.
A comprehensive but understandable and totally medically reliable source for more information is: https://dermnetnz.org/topics/allergies-explained
What is interesting about people though is the tendency to fall foul of the post hoc ergo propter hoc fallacy - essentially a temporal association fallacy where one event is seen to lead to another because they follow in time, whereas they are unrelated and the temporal association is coincidental. "I got my vaccine and X Y or Z happened" is a classic example - in almost all cases the accused occurrence had nothing to do with the vaccine, and the same is true of many things people choose to avoid under the label of allergy.
Sometimes it is a real reaction, more often than not there were symptoms that are unexplained and exposure to a certain product gets the blame unfairly. There are enough people on the internet to make these rumours stick, and of course a few may be true. Just because it's on Social Media does not necessarily make it false.
In terms of 'extractives' I also looked into taxanes from yew in drinking goblets - it's really not possible to get a toxic dose unless you soak sawdust in alcohol for a good long time and here is the key - you are interacting with a surface and that surface represents a tiny proportion of the timber so toxins are limited in quantity and have to adsorb onto any food, most of which is not the type of substance to be good at extracting alkaloids, nor is it in contact with the wood for long. There are exceptions of course with Manchineel, Oleander and Kowhai being well known avoiders for woodwork, but nothing you would commonly consider to be a woodworking wood has significant oral toxicity issues. Anything that will make the user sick will, absent rare allergies, make the woodworker sicker.
This site lists known toxic woods - the red highlights are the key avoiders though as I said, even yew, especially when dry, is not particularly toxic. https://www.wood-database.com/wood-articles/wood-allergies-and-toxicity/
I tend to be on the cautious side of things. Part of that is my general nature; the other part is having worked as a chemist and seeing things go horribly wrong. Juglone (extractive from walunt) was a popular target for natural product synthesis. For a small subset of folks, they can have severe allergic reactions to other. Others have severed nut allergies. As such, if I were making foot contacting items from wood for sale, I would avoid walnut and other woods derived from nut trees. I would also finish it with mineral oil to avoid any potential allergic reactions to nut based oil. Conservative? Yes. Overly cautious? Probably. I see no upside to using a wood that has a potential risk when there are so many other options out there.
I should point out that I have found a few woods just using hand tools (minimal dust plus I don't use sandpaper) that have left me feeling as if I were having minor allergies. When that project was finished, that was the last project I used with that wood. Again, with so many options, why use something that gives you a minor allergy. Fortunately, my favorite wood is cherry and I don't seem to have any allergies to it.