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Wood Guide
By Meg Christensen | Updated June 2025
Wood, and “wood,” in our floors, cabinets, cutting boards, and other home furniture, isn't always what it seems—engineered wood, plywood, MDF, and particleboard contain plastics and formaldehyde-based glues, and even on 100% healthy solid wood, stains and finishes can add another layer of complication. This guide breaks down the difference between solid wood and composite materials, explains what to avoid, and answers common questions like: What does NAF mean? Are vinyl floors safe? Is bamboo really solid wood?
What is engineered vs plywood vs composite vs MDF vs particleboard?
What do you mean by “wood”?
I use “wood” with quotation marks to describe wood-like products that contain a mixture of wood, resins, and plastics. It covers engineered wood, plywood, MDF, particleboard, composite wood, OSB, and others.
What is engineered wood?
Engineered wood consists of thin pieces of solid wood attached with glue to either side of a non- solid wood core. The core can be either plywood or ground wood fibers mixed with resin— basically a glue. The outer solid wood surface is called a veneer. The glue holding the veneers onto the core, and the glue-based binders in the core, are where the health issues potentially lie, since these glues typically contain urea-formaldehyde, a carcinogen and airway irritant.
Happily, some of the newer engineered wood uses bio-based or formaldehyde-free glues that are much healthier than the old engineered woods.
Engineered wood is often used in furniture construction, like in making couches, because it is even stronger than solid wood and can hold up to many years of wear and tear.
What is engineered hardwood? Is it different than regular engineered wood?
No, it’s the same thing. My guess is that this phrasing is a marketing term used to make the product seem a little more like it’s true hardwood.
Is engineered wood toxic?
It depends entirely on what the glue/resin/binder is that holds the wood together. If it is held together with a soy-based resin with no added formaldehyde, for example, then it’s a healthy option. If it is held together with a glue that contains formaldehyde, or a glue that contains other harmful chemicals like isocyanates, then it is harmful to health.
What is plywood?
Plywood is made of many layers of super-thin pieces of solid wood. Each layer’s grain is stacked perpendicular to the one above and below it, and all the layers are attached with an adhesive binder (plywood can have up to 3.5% binder by weight). Alternating the wood grain at perpendicular angles makes plywood even stronger than wood, and is why you see it used for home construction. After the layers are glued together, heat and pressure are applied to make a smooth plywood panel.
Like engineered wood, there are newer, healthier versions of plywood that are made with formaldehyde-free, soy-based resins instead of standard glues. PureBond is an example of a brand that is doing this.
What is composite wood?
Composite wood is very similar to engineered wood, but the materials in the core aren’t always wood-based. Instead, it is often a blend of plastics and wood.
What is MDF?
MDF means medium-density fiberboard and it is made with wood pulp mixed with a resin binder (with up to 10% by weight) to make a wood-like product. This is what IKEA uses in their cupboards, for example, then covers them with a layer of laminate.
What is particleboard?
Particleboard is a type of composite wood made with wood chips mixed with a binder (up to 12% by weight) to make a wood-like product. This is what IKEA uses in its KALLAX furniture, for example.
What are other types of engineered and composite wood?
Oriented Strand Board (OSB), Hardboard, Laminated Veneer Lumber, Glulam, and other wood-type products are some of the other types of engineered wood (and there are a lot!) These are a little different than plywood, MDF, and particleboard for two main reasons: one, they’re not regulated by the EPA to ensure that they contain low levels of formaldehyde, so may have higher levels of harmful off-gassing. Second, they’re less common in furniture, which of course, Interior Medicine focuses on, so that’s all I have to say about them!
What chemicals are in fake wood?
It’s hard to know, unless they disclose them, which is very rare— but here are some brands that do. Formaldehyde, PFAS, BPA, antimicrobials, and heavy metals are the worst offenders. These are most commonly mixed in with luxury vinyl flooring. I follow Green Science Policy’s “6 worst” chemical classes to avoid.
Formaldehyde in Wood
Does all wood have formaldehyde in it?
Yes, trees emit 9ppb (parts per billion) of naturally occurring formaldehyde, so therefore, all wood contains some. This is why the term “no added formaldehyde” or NAF is preferred for wood and “wood” products— it’s more technically correct. The laws passed in 2010 that regulate added formaldehyde-based resins in “woods” like plywood, particleboard, and MDF, limit the formaldehyde emissions to 90ppb. That’s 10x above naturally occurring levels in wood, but still significantly lower than the levels allowed before 2010.
What is NAF engineered wood (and ULEF?)
NAF stands for “No Added Formaldehyde.” This means the binders used to glue the wood together don’t contain urea-formaldehyde.
ULEF means Ultra-Low Emitting Formaldehyde, and may be achieved by adding a chemical that sequesters, or captures, formaldehyde from escaping. These are called Formaldehyde Scavengers. It may also mean there is a blend of formaldehyde and non-formaldehyde based binders.
Composite wood that is “CARB or TSCA compliant” means that it has low formaldehyde levels, but not ultra-low. Since 2019, all plywood, MDF, and particleboard manufactured or imported into the US must be compliant.
Faux Wood Flooring
Is vinyl flooring toxic?
Yes. Luxury vinyl plank, or LVP, is deeply un-luxurious— it’s cheaper than wood, made of plastic, and is harmful to people and the environment. Polyvinyl chloride is the type of plastic it’s made out of, and is widely regarded as the least sustainable and least healthy choice of plastic flooring available.
What chemicals are in LVP?
LVP’s core material is polyvinyl chloride, or PVC. PVC is made with vinyl chloride, a well known carcinogen, that harms workers and people close to factories. It is softened to make it more comfortable to walk on with plasticizers including phthalates like BPA and other endocrine disrupting chemicals. The top layer is a coating that looks like wood; some brands are coated in PFAS to make them more wear and water resistant.
Are vinyl floors safe?
No. Even though most LVP doesn’t off-gas VOCs as strongly as versions made a few years ago, and many are made without BPA now, but that doesn’t mean they’re safe— especially for babies and kids in close contact with their hands and mouths.
What should I do if I already have vinyl flooring?
If you can replace it with solid wood, non-toxic engineered wood, or linoleum (which is made of flax!), then that’s ideal. That said, it’s often way outside the budget to do so, or you might live in a rental. In either of those cases, use natural rugs to protect your feet and any kids or babies hand and mouth contact with the floor. Mop or wet-vacuum often to remove any microplastics or chemicals that shed off from it with wear and tear and become part of the dust. Above all, don’t stress, and remember that your home is one part of your health.
Is laminate flooring safe?
Laminate flooring can be safer than LVP. It can have some wood in its core, or be 100% plastic, depending on the brand. The top layer is a piece of fiberboard with a photo of wood laminated to the top, then covered in a wear-resistant coating. This coating can be scratch-resistant, or water-resistant (which often means it contains PFAS).
Is bamboo solid wood?
Sometimes! Bamboo is technically a grass, and can be solid, or more like engineered wood, when used in home products. Solid bamboo is rarely, but sometimes used as flooring. More often, like you see in butcher blocks or cutting boards, bamboo is processed in a vertical or horizontal fashion, a lot like plywood— thin strips of bamboo are glued and compressed together to make a strong, solid board. Or, bamboo veneers are glued to cores made with a variety of materials, depending on the brand.
Wood Stains
Are wood stains toxic?
Wood stains are often, but not always, toxic to health. It depends completely on the kind you use. A completely natural wood stain like coffee is obviously safe. Water-based wood stains are relatively non-toxic, especially ones with certifications like GreenSeal-11 ensuring the most harmful additives are avoided. Ones without VOCs, antimicrobials, chemical drying agents, or heavy metals are a better choice. Oil-based wood stains with standard chemicals that release high VOCs are quite harmful to health.
What is a 100% natural wood stain?
While I don’t know of any that come in a purchasable can, people do use coffee grounds, tea, walnut husks, and other natural materials to stain wood. Since these are generally less permanent, they require a finish on top to seal them in.
Wood Finishes
What is the difference between wood stain and wood finish?
Wood stains add color to natural wood, while a finish protects it.
Why are oil-based finishes, but water-based stains, better?
Natural, oil-based finishes like linseed oil, hemp oil, or tung oil are minimally processed, and very low in VOCs. Water-based finishes often contain high-VOC, toxic solvents to make them work better. On the other hand, natural, oil-based stains typically have higher VOCs, whereas their water-based counterparts, have less.
What are plant-based oil finishes?
Linseed, hemp, and tung oil are types of plant-based oil finishes. Linseed oil comes from the flax plant. Hemp oil comes from the cannabis plant. Tung oil comes from the Tung tree (Vernicia fordii), native to China, Myanmar, and North Vietnam.
Is mineral oil safe?
Now it is relatively safe, as long as it is highly refined and purified. Mineral oil comes from petroleum, and in the past, it wasn’t refined as well, so it contained carcinogenic polycyclic aromatic hydrocarbons (PAHs) and other impurities. Now, the refining process is better, and highly refined and purified mineral oil is generally considered safe for use in cosmetics and food. It is not known to be carcinogenic to you in this version of itself and is an ingredient in candies like Swedish Fish, and is applied to many cutting boards and wooden utensils and serving dishes because of its water resistance. I consider it so-so. It is not directly carcinogenic to you, but it depends on petroleum extraction, solvents, and refineries, which is not good for people or planet long term, and I don’t consider it as safe as a plant-based finish.
What are solvent-based finishes?
Varnish, acrylic, synthetic lacquer, and urethane-based finishes all require a much higher solvent concentration than water-based finishes, so are quite high in VOCs that irritate your respiratory tract and can cause other issues. They also often contain carcinogenic chemicals.
Is shellac toxic?
It depends if you’re talking about natural shellac or synthetic shellac. Natural shellac comes from the cocoon-like secretions of the female lac bug, and has been used for thousands of years. Synthetic shellac contains solvents, and has a harmful vapor.
Sustainability vs Human Health in Wood
What is FSC certified wood?
FSC, or the Forest Stewardship Council certification, is focused on responsible management of forests. For wood, it means that the trees it comes from meet forest management standards, indigenous people’s rights are respected when harvesting, and old growth forests are not disturbed. It’s a fantastic certification in terms of our environment and community, but FSC-certified wood can still be treated or finished with many other chemicals that harm your health.
About “Non Toxic” and Other Language
A quick note about how I use the terms non-toxic, chemical, and toxin:
I understand that there is no agreed-upon definition of the term non-toxic, and that everything, even water, is made of chemicals, so nothing is truly chemical-free. Likewise, I’m aware that toxin refers to a natural substance like a plant poison or venom, whereas toxicant is a more accurate term for the chemicals in products that have a negative health impact. I choose to use these words anyway because they are currently the most culturally agreed-upon, descriptive, and accessible terms that allow people to find the information they are seeking.
Some people really care about the accuracy of this terminology, so I’m letting you know!
Wood Rating Scales
Rating scales for wood, finishes, and stains. These scales keep me consistent and unbiased as I rate and rank products in the Interior Medicine shop, and hopefully they’re helpful for you, too.
Having three (optional) scales captures a more complete picture of wood’s level of material health by considering three things: the wood itself, and if it is treated with a stain and/or a finish. For example, an ultra-healthy piece of 100% solid hardwood may be stained with synthetic stain and finished in polyurethane, making it unhealthy. On the other hand, a composite wood product containing minimal formaldehyde may be finished in a plant-based oil, making it potentially healthier than the first example.
Wood or “Wood” Type
Wood Stain
Wood Finish
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Healthiest Cutting Boards
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