Wood Toxicity
8th in a series of articles by Barb Siddiqui

Sometimes, if you are given, or have purchased, an exceptional board in a species you haven't worked before, the beautiful figure or spalting pattern in it can make you think you're holding the ambrosia of the gods. But did you know some wood species could actually be hazardous to your health?

Since mankind began interacting with plants, toxic substances have been used from the leaves and bark of various trees. Latex comes from rubber trees, the resin of pine trees is used to make turpentine, and tannin from oaks and other plant sources is used to make medicine, ink, and to tan leather. Camphor trees yield a crystalline volatile solid used for insect repellent and even for explosives. It stands to reason that machining the inner wood structure of some species might cause us problems.

The main culprit to be wary of is fine wood dust, most often encountered when sanding the material. It's not only the exotics and imported species you need to keep your eye on, but many domestic species can cause skin rashes, eye irritation or breathing difficulty.

Some studies have indicated that long-term exposure to working such wood can cause asthma or possibly even nasal cancer (see Sources at end of article.)

Several woodworkers have noted that allergic reactions to wood dust occur more often in the summer, and it is known that a woodworker's own perspiration encourages fine dust to stick to the skin, prolonging exposure. Also, wet sawdust, as when milling your own wood from felled trees, is more likely to stick to the skin than the dust from dried lumber. If a woodworker mills her own wood, it is best to do it in winter, when the trees are dormant. Hardwood sap has then receded into the root system, and toxicity is less likely to be a problem.

Molds can also trigger allergic reactions, and woodworkers should take extra precautions when using spalted material. Another mold to be aware of is mold grown in damp piles of sawdust. It's best to keep a workshop clean and dry. Regular vacuumings are a must.

What specific woods should you watch out for? Some of the more potent species reported are teak, lacewood, satinwood, rosewood, oleander, iroko, cocobolo, black locust, greenheart, padauk and hemlock, among others.

Some woods are classified as 'irritants,' meaning a reaction is noticed soon after exposure and goes away, then is noticeably repeated. Others are classified as 'sensitizers,' and have more serious reactions that may show up months later, causing your body to react more severely each time exposed. Most of these woods affect the skin, eyes, and/or the respiratory system.

Some common woods many woodworkers have reacted to are: cypress, ebony, African mahogany, oak, olivewood, redwood, sassafras, snakewood, walnut, wenge, willow, western red cedar, yew and zebrawood. Ash, beech, birch and maple also make the list, but more due to fungal contamination than the wood chemistry itself.

Preventive measures aren't really all that difficult. Once you're aware of the problem, it's a matter of both limiting your skin and eye exposure, and not breathing in the dust. A good dust mask is a first defense, whether sanding, cutting or routing. Long sleeves will help, if they aren't baggy and presenting a safety hazard. When you know you are working one of the more toxic species, button up your collar, and you may want to wear thin leather gloves such as tight goat skin. Many rashes are first noticed on the webbing between fingers. Goggles or wraparound safety glasses will help, as will washing out the eyes after a session of woodworking to irrigate any dust buildup. General cleanliness is important. It is just plain good sense to shower after working wood, because the less exposure your skin has to wood dust, the less chance of rashes, blistering or infections. Soap and water works wonders.

With these personal warnings covered, the most sensible place to stop irritation from happening is at the source of the work. If you don't have a dedicated dust collection system, use a shop vacuum (or several) to make task-specific dust collection for each procedure. Put the wide floor nozzle attachment on the hose and anchor it with light C-clamp pressure near your sanding area. You can make a plywood collar that traps the nozzle in a frame and can be clamped to a work table or a drill press table to gather up the dust. Also, be sure your shop or workspace is well ventilated, with airflow coming in behind the operator, whether from a window or a fan, and carrying any dust particles away from you and your workpiece, vented to the outside. Ambient air filters are a help, but in dealing with toxic wood dust, the real solution is in catching it at the source, immediately where you are working.

People react differently to these toxins, sometimes making an 'irritant' act like a 'sensitizer.' Some woodworkers show no reaction to a locally grown species, but notice a reaction when working the same species grown elsewhere. Pay attention to your body's signals. If you notice head congestion and a little nausea that goes away after you quit working a wood species, try to notice if it occurs again when you go back to work.

If you have an allergic reaction to wood or wood dust, be sure to tell your doctor what you have been working with. People prone to allergies may react more quickly and violently to the more toxic wood species. Outside factors have also played a role; alcohol consumption or even a recent series of bee stings can combine with exposure to toxic wood dust and cause violent physical reactions.

One last caution: pressure-treated wood. Those 4x4 posts, faded green and with the little tick marks all up and down them, are great for sinking in the ground to anchor your deck. But they are impervious to rot because they are treated with Chromated Copper Arsenate. You don't want to cut, sand or work this wood in a closed shop, and don't burn the cut-offs. It is worked outdoors, and any leftovers should go out with standard trash collection. Wear long sleeves and a good dust mask when working it, then launder all clothing afterward separately. The preservative chemicals have been proven to be safely bound in the wood fibers, but the dust from working pressure-treated wood is truly nasty stuff. Woodworking, like many activities, is inherently dangerous, and knowing about the dangers is the first step in preventing them. Some of the most beautiful woods may be the ones that require the greatest care in handling them, so be informed and work safely.

Additional sources for more information:

Annapolis Woodworker's Guild

Ontario College of Art & Design: Woodshop

U.S. Environmental Protection Agency website

Stanley Wellborn: 'Health Hazards In Woodworking'
from Fine Woodworking On The Small Workshop, p. 70

Gary Mustoe: 'Respiratory Hazards'
from Fine Woodworking On The Small Workshop, p. 74

Charles Self: 'Woodworker's Guide To Selecting & Milling Wood'
Betterway Books, 1994. pp. 98-100

Jon Arno: 'When Wood Fights Back'
Fine Woodworking magazine, Sept/Oct 1995, p.65