There is no doubt that some woods can be potentially toxic to some
people. The question is always one of "what degree". This
cannot truly be answered. Each individual has different degrees
of resistance, some more prone to allergic reactions, and others
not so. Every day our knowledge of tree biology and chemistry grows,
leaving us with more information, but also more questions. How all
this relates to each individual is impossible to know. All we can
say is "be cautious". Use new woods in a limited way, one day then break for two days to see if you have a reaction. Use proper respirators, until you know that it has no adverse reaction
with your body.
Toxicity of wood can mean a lot of different things to different
people so here are some basic concepts of wood toxicity, some natural
and some man-made:
Natural Chemical Poisons:
This normally refers to chemicals produced by the tree. It has been
suggested that these chemicals originated as part of the tree’s
natural defense system against insect and other animal attack. They
tend to be present in higher concentration in the sap, bark and
foliage of the tree, and to a much lesser extent in the trunk. For
example, the foliage of black cherry contains a precursor of cyanide,
but yet we work with the wood with little difficulty. Woods that
are naturally oily, even after kiln drying are much more likely
to cause an allergic reaction, just because the wood’s oil can transfer
onto your skin more easily and enter the blood stream. The reaction
can range from that of a mild irritant, to something that is truly
toxic and lethal, although the latter is very rare.
Natural Physical Poisons:
Fine wood dusts, even if they have no chemical toxicity, can pose
a health risk. Dust can act as an irritant to the skin and particularly
to the respiratory tract of people that have a natural sensitivity
in this area. Western Red Cedar has an extremely small dust particle
size, prone to penetrate deeply into the lungs and cause severe
reactions in asthma sensitive people. Wear a dust mask! Have good
dust extraction equipment working in your shop.
Nature can introduce toxins as the wood rots on the forest floor.
Fungal spores and bacteria that invade a rotting tree, creating
beautiful spalted wood, but can be toxic if they are able to invade
the human body. See the section on spaltic wood for more information.
Mankind has also introduced toxins into wood. Every time the wood
is chemically treated with products like creosote to prevent rotting.
Formaldehyde glues are used extensively to glue plywood layers together
in both sheet materials and flooring. In sawing these materials,
the dust generated introduces these toxins back into the air. Many
of these glues emit vapours long after the manufacturing process
has been completed. Both the dust and the vapours can be very toxic.
The Last Word...
Be cautious...just because something doesn't cause a reaction the
first time doesn't mean you'll never have an allergic reaction.
Your sensitivities can build with exposure. Allergy-prone people
should be more cautious in the woods they chose and everyone should
limit exposure to sawdust of new woods the first few times you work
Have fun, but be healthy! Think about exotic wood toxicity as it
relate to YOU.