By Mac Simmons

Wood	Reaction	Site	Potency	Source	Incidence
Bald Cypress	S	R	1	D	R
Balsam Fir	S	E, S	1	LB	C
Beech	S	E, S, R	2	LB, D	C
Birch	S	R	2	W, D	C
Black Locust	I, N/M	E, S	3	LB	C
Blackwood	S	E, S	2	LB	C
Boxwood	S	E, S	2	W, D	C
Cashew	S	E, S	1	W, D	R
Cocobolo	I, S	E, S, R	2	W, D	C
Dahoma	I	E, S	2	W, D	C
Ebony	I, S	E, S	2	W, D	C
Elm	I	E, S	1	D	R
Goncalo Alves	S	E, S	2	W	R
Hemlock		R	?	D	U
Iroko	I, S, P	E, S, R	3	W	C
Mahogany	S, P	S, R	1	D	U
Mansonia	I, S	E, S	3	W, D	C
Mimosa	N/M	?		LB	U
Myrtle	S	R	2	LB, D	C
Oak	S	E, S	2	LB, D	R
Obeche	I, S	E, S, R	3	W, D	C
Oleander	DT	N, C	4	D, W, L	C
Olivewood	I, S	E, S, R	3	W, D	C
Opepe	S	R	1	D	R
Padauk	S	E, S, R	1	W, D	R
Pau Ferro	S	E, S	1	W, D	R
Peroba Rosa	I	R, N	2	W, D	U
Purpleheart	N/M		2	W, D	C
Quebracho	I	R, N	2	D	C
Redwood	S, P	E, S, R	2	D	R
Rosewood	I, S	E, S, R	2	W	U
Satinwood	I	E, S, R	2	W, D	C
Sassafras	S	R	1	D	C
Sequoia	I	R	1	D	R
Snakewood	I	R	2	D, W, LB	R
Spruce	S	R	1	W, D	R
Walnut, Black	S	E, S	2	W, D	C
Wenge	S	E, S, R	1	W, D	C
Willow	S	R, N	1	D, W, LB	U
Western Red Cedar	S	R	3	D, LB	C
Teak	S, P	E, S, R	2	D	C
Yew	I,DT,N/M	C, E, S	4	W, D	C
Zebrawood	S	E, S	2	W, D	C
Reaction: I - Irritants; S - Sensitizer; P - Pneumonitis Aveolitis; Hypersensitive Pneumonia; DT - Direct Toxin; N/M - Nausea/Malaise
Site: S - Skin; E - Eyes; R - Respiratory; C - Cardiac; N - Nasal
Potency: 1 is the lowest potency, 4 is highest
Source: D- Dust; LB - Leaves/Bark; W - Wood
Incidence: R- Rare; C - Common; U - Uncommon
Chart information courtesy of Petr Hovacek, Mendel University, Czechoslovakia

Many articles have been written about hazards in the chemicals used to finish woodwork. But there is not enough written about the dangers in the woods themselves. My intention for writing this article is not to scare or frighten readers, but to inform and alert them to the health hazards and toxic reactions possible when working with different species of woods. I hope to increase their awareness regarding factors that can affect their health and help them decide whether they need to take any precautions to protect themselves.

Some reactions that are caused by certain chemicals are very similar to the reactions caused by some woods. In fact, some conditions may be blamed on one material, while actually being caused by the other one. In addition, adverse effects may not appear until after a long period of exposure. I know several woodworkers who worked with various species of woods for years before becoming sick. This is why I want to alert you to the possibility of suffering a reaction to toxins and irritants whenever you are working with wood.

Handle with care
Everyone who handles, cuts, sands and assembles wood should be aware that they could have a minor or major reaction to different species. These reactions can be so subtle, you may not even be aware of them happening because of the low sensitivity to their effects. In some cases, the body builds up its own defenses and reactions are not severe, while in others people have very bad reactions just from touching the same species of wood.

Reactions also can occur from inhaling sawdust or from sawdust settling on skin. Reactions can occur the first time you come into contact with certain woods or only after working with them for years. Some toxins are accumulative and you will not feel their effects until you have reached an unknown quantity of the toxins in your body.

In considering the differences between softwoods, hardwoods and exotics, sawdust from hardwoods, especially from the exotic species, are sensitizers and can cause allergic skin reactions, eye inflammation, hay fever, asthma, coughing and respiratory diseases. Highly toxic species include the giant sequoia, hemlock, yews, cypress, cork oak and other oaks, beech, rosewoods, some maples, redwoods and western red cedar.

Softwoods do not cause as high a frequency of skin or respiratory problems as hardwoods, although some individuals develop allergic reactions to some softwoods. The sap present in many green woods can cause skin allergies and irritations from direct contact.

Also, minor and major reactions to certain woods can include pneumonitis alveolotis (hypersensitivity pneumonia); permanent lung scarring (fibrosis); headaches; salivation; thirst; giddiness; nausea; dizziness; irregular heartbeats; skin, eye or respiratory system problems; cardiac conditions and malaise. The wood, sawdust, leaves and bark of the trees can cause all of these conditions. (See chart on page 36 for details.) In addition, there have been studies that link wood dust to nasal cancer in rare cases. Wood dust studies are ongoing to determine any negative effects.

The chart contains some woods that have toxins, irritants and sensitizers. This list is not intended to stop you from using any of these species, but only to inform and alert you about the risk of working with them.

Care also must be taken when working with plywood, composition board or other materials that contain chemicals like urea-formaldehyde, phenol-formaldehyde resin glues and wood preservatives like CCA (chromate/copper/arsenate), creosote, zinc, copper napthenate and other chemically treated woods.

Prevention is your best cure
Avoiding problems can be as simple as using a soft cap, gloves, eye protection, an apron, work jacket or dust respirators that are NIOSH-approved. A good dust collection system suited for your shop's size also can be an investment for good health. These items will help protect you from the dangers of handling wood and inhaling sawdust or having it settle on your skin.

Protective gear should also be used whenever you empty sawdust from saws, lathes, joiners and collectors. You should wash your hands after working with, or handling, any wood. You also should inform your fellow woodworkers about the "dangers in the woods" whenever you are teaching your craft. Always start with safety and protect against potential risk from certain woods which can affect a person's health in the future.

Woodworkers should show the same respect for the woods we work with as we do for the power tools and hazardous chemicals we use in our shops. A little care can go a long way.