Toxic Woods

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As anyone who has gotten a rash after working with wood can attest, some woods just "don't agree" with people.

    Many wood species are only slightly toxic, and then only to people who happen to be allergic to them, while other woods are deadly to anyone who comes into close contact with them.  There are stories of soldiers dying after drinking from canteens made of yew, and people and cattle being made sick or killed by eating seeds or flowers of the mescalbean tree, from which can be extracted the alkaloid narcotic mescaline.

P R O T E C T I N G   Y O U R S E L F 

    To understand how different toxic woods may affect you, you first need to know the difference between the types of toxins or allergens they contain.  Some woods contain irritants and some are sensitizers, while a few are labeled as direct toxins.  An irritant is simply a substance which irritates, and can cause problems with anyone after sufficient exposure.  Cocobolo is a well known example of a wood whose heartwood contains an irritant, and after sufficient exposure, anyone can develop contact dermatitis from overexposure to cocobolo dust.  A sensitizer is a substance to which you must first be susceptible, like an allergy.  Symptoms may not develop for some time, but once they do, they tend to get much worse with each exposure.  I have known a few people who developed severe asthmatic reactions after breathing sanding dust from zebrawood, yet most people have no reaction at all.  The third class, direct toxins, are exactly what the name implies, toxic.  An example of this is yew, which, if made into canteens or barrels, can leach the alkaloid poison taxane into the water.  The key here is to know which type of toxin you're dealing with, how potent it is, and how you may be exposed.  Simply handling a dry piece of yew is not likely to cause problems, and cocobolo is often used for knife handles and pistol grips, again without any ill effects.

    The major form of exposure to most woodworkers is to wood dust.  Powdered bits of wood have more exposed surface area than solid wood, thus they can react more potently with our bodies.  If a liquid, such as sweat, is present to leach out the chemicals and spread them over the skin, or the dust is inhaled, the exposure becomes even greater.  The worst case is when working green wood, which produces sap-filled, sticky dust and shavings.  Naturally, using a dust collection system, wearing appropriate masks or respirators when working toxic or spalted wood, and keeping your shop clean and relatively dust free are the best ways to prevent adverse reactions to wood.  Here are some more specific ways to avoid exposure to potential allergens and toxins in wood:

Whole-Shop Dust Protection (Dust Collection)
Dust collection can be divided into two types: primary and secondary systems.  Primary dust collection occurs at the source of the dust: a tool has a dust shroud and port, to which a dust collector or vacuum is connected.  There's always a little dust that gets by the dust shroud, though, so a secondary dust collection system, such as an air filtration unit, gives you an extra layer of protection against breathing too much dust.  When purchasing dust collection or air filtration units, try to get the ones that filter out 99% or more of particles down to one micron in size.  Physicians say that it's the particles between about three and ten microns that are the worst, since they are small enough to get down into your lungs' alveoli.  That's where they can have more-or-less direct contact with you bloodstream and do their worst.  A good dust collection system can also extend the life of your equipment, and make your shop a much more pleasant place to work.  The problem with dust collection is that the dust collector eventually fills up and need to be emptied, which leads to dust exposure, and the dust has to get by you in order to reach the filtration unit, so you'll be exposed to at least some dust there also.  That's where personal protection comes in.

Personal Dust Protection
Personal protection picks up where whole-shop protection leaves off.  It stops the dust from being inhaled or contacting your skin, and you remove it when you leave the shop, thus minimizing all potential exposure to toxins or allergens from the wood.  Personal protective equipment consists of clothing that blocks dust from reaching the skin, and masks that block dust from being inhaled.  Long pants that cover the tops of high-topped boots keep dust from your lower extremities.  A long sleeved shirt can protect your torso and arms, but remember to roll the sleeves up before using power tools, or they might get caught in the moving parts.  Buttoning the collar and un-tucking the shirt can give chips a way to escape when you're really making a mess, as with a chainsaw or on the lathe.  A hat shields you from dust falling from above.  (How it all gets up there I don't know, but a lot of it does.)  Ballcaps are popular, but I prefer a short-brimmed cloth cap, because the button of a ball cap hurts when it gets under the headband of a pair of ear muffs (hearing protection), and the long brim gets in the way.  Sometimes I'm able to wear gloves to minimize dust exposure on my hands, but in a world of power tools, it's not very often that you can safely wear gloves.

    Finally, to avoid that fine, inhaled dust (the most dangerous kind), there's a respirator.  I don't use dust masks, because they are NOT designed for protection against harmful dust or contaminants.  Many actually have a notice to the effect that they are NOT OSHA APPROVED for such use.  A better option is a respirator with one micron or finer filters on it.  3M makes a comfortable half-mask respirator that is widely available, not too expensive (maybe $40, which includes particulate and charcoal filters), and uses one micron filters.  The charcoal filters on these are designed for filtering out organic vapors, such as finishing solvents, which can also cause serious health problems with frequent overexposure.  Some masks actually boast HEPA filters, which stop 99.9% or more of all particles down to 0.1 micron in size -- great for those with severe allergies or asthma.  Of course, read and follow the manufacturer's instructions, and if the filter appears saturated with dust or you smell solvent odors, replace it immediately.  If you experience itching, rash, dizziness, nausea, sneezing, loss of vision, or difficulty breathing, you should stop working with wood or chemicals immediately and contact a physician.