|Woodworkers need to take precautions against dust when working with any lumber, whether the wood is domestic or exotic. Wood dust is no good for your lungs or eyes, and some wood dust can also react with your body. Possible reactions include skin rashes, watery eyes, respiratory problems, headaches, dizziness, or nausea.
The degree and type of reaction depends on an individual’s susceptibility to certain allergies, as well as the concentration of dust and the amount of time exposed to dust. The same reactions from person to person are not always a certainty.
In general, toxicity is in one of three categories: irritation, sensitization, and poisoning.
Skin, respiratory tracts, and mucous membranes get irritated easily by any fine dust because dust absorbs moisture, thereby drying out the surface with which the dust is in contact. Itchy skin and sneezing are examples of basic irritation thanks to wood dust. The level of irritation is proportional to the exposure time to, and concentration of, wood dust.
But irritation is not necessarily benign. Woods like walnut and rosewood emit pleasant odors with low levels of dust, which most woodworkers equate with being one of the benefits of working with woods. However, the natural substances in these woods that cause the scents are also potentially toxic with greater dosage exposure and concentration. Long term effects of exposure to wood dust can include developing an allergic reaction to the dust or possibly nasal cancer.
Substances in wood that cause an emerging (and potentially serious) allergic reaction after repeated exposure are called sensitizers. This type of toxicity is specific to individuals and takes time to develop – some people may experience a significant reaction to a wood while others do not. While sensitization typically takes time and repeated exposure to develop, it is possible for some individuals to have an allergic reaction to a wood upon their first contact.
Even if you do not have any reaction to a wood (or its dust) the first few times you use it, it’s still vital that you take precautions and avoid as much exposure as possible. It’s possible that your body will develop a reaction the more you are exposed.
Universally lethal chemicals are rarely found in natural wood that’s available on the commercial market. Most poisons in plants and trees are located in the bark and/or sap – there are some exceptions for rare woods.
Sometimes poisonous chemicals are introduced to wood products, such as with pressure treated lumber. Hardwoods cut for cabinetry, flooring, and furniture are not pressure treated.
Some common woods demand that woodworkers be aware of their own allergies. Those who have an allergic reaction to aspirin should avoid using woods from birch and willow trees (Betula spp. and Salix spp.) because these contain good concentrations of salicylic acid, the key ingredient in aspirin. See A Guide to Useful Woods of the World Appendix B for more.
You should limit your exposure to wood dust by doing the following things.
- Use vacuum dust collection in your shop, and keep your shop ventilated with fresh air.
- Use protective equipment while woodworking: dust mask, goggles or a full-face respirator, and a protective barrier cream on your arms or exposed skin.
- Immediately after woodworking change your clothes, washthem, and take a shower. This will prevent transferring wood dust to your house where you or your family may be repeatedly exposed to it.
What about toxicity of wood in my finished project?
Baby cribs and food utensils are popular projects, and ones that woodworkers are often curious about “safe” woods and finishes. The short: a sealed and finished wood poses no toxic risk.
What about the sealer or finish then? Solvent-based finishing products (lacquer, varnish, etc) are highly toxic in their liquid state, but cured lacquer and varnish finishes are perfectly safe.
For projects that come in contact with food, such as salad bowls and cutting boards, you really don’t want a hard shell finish (lacquer or varnish) that can chip or rub off. Mineral oil, teak oil, and butcher block oil are all popular and safe choices for these projects.
A popular finish for baby cribs is shellac, as the FDA approves this for use in the capsules of medications. This approval makes many woodworkers feel that shellac is more safe than other finishes. But cured lacquer is safe, as is any cured solvent- or water-borne finish.
For more comprehensive information regarding wood toxicity, see Appendix B in A Guide to Useful Woods of the World (ISBN 1-892529-15-7)