Health Hazards in Woodworking

by Stanley N. Wellborn

Industrial woodworkers have long recognized the risks of
their trade. But it has been only in the past few years that artists
and craftsmen have become concerned about-or even
aware of- the many hidden dangers in woodworking.
Of course everyone recognizes those hazards that cause
immediate and traumatic inj ury-blades that cut fingers and
limbs, wood chips and fragments that fly into eyes, loose
clothing or long hair that catches in whirling machinery,
smashed fingers and toes, muscle strains from heavy lifting .
But now medical authorities in the United States , Canada
and England cite a number of insidious causes of disease that
can be directly attributed to woodworking. Their list includes
wood dust, sap and oils , mold and fungus, chemical additives,
toxic solvents and adhesives , vibration and noise.
A diligent search of medical literature, or a chat with an
industrial hygiene specialist , will turn up dozens of horror
stories about the health hazards of woodworking . For example
, the 4 3 -year-old woodworker who had operated a lathe
for more than 2 5 years and became worried about a persistent
sinus irritation and sore throat. His doctor prescribed a
standard treatment , yet the condition did not improve . Finally,
lab tests revealed cancer of the nasal passages . Or the
art student who broke out in a rash , with blisters resembling
second-degree burns, shortly after she began to sculpt wood .
When she stopped woodworking, her skin healed .
The mere existence of a medical case history does n ‘ t mean
every woodworker will succumb to serious disease ; the biggest
unknown is often the size of the risk. In most cases, woodworkers
can take adequate precautions for relatively little cost.
Common protective measures are described in the box on
page 56. Woodworkers who notice something wrong with
their health would be wise to suspect something in the shop ;
some potential problems are discussed below

Respiratory ailments
Health authorities warn that woodworkers should be most
on guard against inhaling foreign substances.
To most woodworkers , concern about the cancer-causing
potential of wood dust overrides all other health worries .
Indeed , this concern appears justified, at least on the surface.
Woodworkers are 500 times more likely to have certain types
of nasal cancer than non-woodworkers . However, the risk of
developing cancer solely through exposure to wood dust is
quite low.

” The statistics on cancer in woodworkers can be made to
sound quite alarming , ” says Dr. Julian A . Waller of the University
of Vermont Medical School and an authority on health
hazards in the arts. ” But the actual risk advances only from
‘extremely rare’ to ‘ rare . ‘ Only one woodworker in 1 ,400 will
get this cancer, and at that after an average of 40 years of exposure.

Nevertheless, in various health hazard evaluations conducted
by the National Institute of Occupational Health and
Safety (NIOSH) in Cincinnati, Ohio, investigators have concluded
that wood dust is at least a contributing factor in the
development of some other types of cancer. In a report prepared
after an evaluation of the Cooper Union School of Art
in New York City, the Institute cites studies pointing out that
“cancers of the larynx, tonsils, tongue and lung have been
reported to have resulted from inhalation of wood dust ”
among furniture workers in England and Sweden .
In addition, the NIOSH report mentions that many researchers
have found that the normal functions of the mucous
membranes in the nose, throat and lungs were impaired in
workers exposed to wood dust for more than ten years .
Among the most recent and thorough research on this
problem is a study done by Dr. Samuel Milham , Jr. , of the
State Department of Social and Health Services in Olympia,
Wash . He reviewed the death records of more than 1 6 ,000
members of the United Brotherhood of Carpenters and Joiners
of America, and found that the results supported the hypothesis
that wood contains carcinogens . The study also
found an above-average incidence of leukemia and lymphoma
among millwrights, lumber workers and cabinetmakers.
Although risk of cancer from exposure to wood does appear
to be low for most woodcrafters, the incidence of other forms
of respiratory illness is high . At one time or another, virtually
all woodworkers have suffered irritation of the upper respiratory
tract after breathing sawdust. The condition is usually
transient and produces coughing, wheezing and tightness in
the chest. Frequently , however, long-term exposure produces
” fogged lungs” on X-rays and a type of occupational asthma
that can become virtually permanent .
Redwood dust, for example, is the cause of sequoiosis, an
acute illness that resembles pneumonia. It usually appears
within a few hours after exposure, and its symptoms are
shortness of breath, bronchio-constriction, dry coughing,
chills , sweating, fever and general malaise. Repeated episodes
of this ailment can cause permanent scarring of lung tissue.
Wood dust from another tree, the Western or Canadian
red cedar, causes similar symptoms that can develop into
asthma or rhinitis, an inflammation of the nasal passages .

Medical researchers believe the causative agent in red cedar is
plicatic acid, which is thought to give the wood its characteristic
fragrance. Lumber workers in the Pacific Northwest are
frequently affected by cedar dust. One medical case history
tells of a 30-year-old worker who could breathe at night only
by kneeling on his hands and knees . When he left the woodworking
industry, he regained his health.
Another source of respiratory difficulties is the mold and
fungus that grow in damp areas of the shop , particularly in
piles of sawdust. Mold has also been known to cause serious
reactions in skin and fingernails after continuous exposure.
Occupational health experts agree that the obvious and
best way to prevent respiratory problems is to cut down the
amount of airborne dust in the shop. Although no specific
environmental standards fo r allergenic wood dust have been
established by the fe deral Occupational Safety and Health
Administration (OSHA) , the American Conference of
Governmental Industrial Hygienists has set a provisional (and
very low) limit on ” nuisance dust” of 5 mg per cubic meter of
air space. A few minutes of steady hand-sanding normally
produce about 15 mg per cubic meter in the immediate work
area ; a portable or stationary belt sander will generate about
150 mg per cubic meter. Without ventilation, the dust will
remain airborne for hours and spread through the shop .

Skin irritations and allergies
A large number of wood species will produce skin irritation
or glandular swelling in sensitive individuals who are directly
exposed to their dust, oil or sap. Some woods, such as West
Indian satinwood and mansonia, are classified as ” primary irritants”
because they are highly toxic and are likely to produce
skin eruptions or blisters in most people on first contact.
Others, such as cocobolo, are “sensitizers” that may cause
allergic dermatitis only after repeated exposure .
A number of domestic U. S. woods have been mentioned .
in medical literature as causing skin irritatio ns, such as hives
and rashes , but such skin reactions are actually quite infreq
uen t, occurring in less than 2 % of the populatio n. However,
the problem becomes much more serious with tropical or exotic
woods . A partial list of toxic timbers is given in the box
on this page .
Dermatologists who have investigated wood allergies note
several common characteristics . Allergic reactions are more
pronounced during the summer, or when a person ‘s skin is
moist fr om perspiration, or when the wood dust itself is
damp . Reactions are more fre quent among persons older than
40 . Freshly cut wood is much more likely to be an irritant
than older, seasoned wood. Occasionally, a wood species from
one geographic area will not affect a woodworker, while the
same species grown somewhere else will.
In most cases, it is the heartwood rather than the sapwood
that is responsible for skin allergies, and it is the accessory
substances, or “extractives ,” from the heartwood that produce
the toxic effects. Extractives are whatever can be leached
out of the wood (with water or other solvents) without
changing its structure. These powerful chemical components-
resins, alkaloids, tannins, acids , salts and gums-vary
widely fr om species to species and even from log to log. In
some trees they make up as much as 20% of the wood structure.
Most woods contain about 4% to 10% extractives . The
effect of extractives can be devastating. One report cited a
serious outbreak of dermatitis among workers at an English furniture plant that used mansonia wood . The entire operation had to be shut down for weeks .
Obviously , the occasional case of dermatitis won ‘t discourage
woodworkers from continuing to use exotic woods .
The best path to follow is one of prevention , including dust
control , protective clothing, washing and shower facilities and
barrier creams , such as DuPont’s Pro-Tek. Persons who suspect
they are sensitive to certain woods should have a doctor
do a skin-patch test to find the cause of the allergy .
Pesticides and preservatives introduced to wood while it is
being timbered, processed and shipped may also cause dermatitis.
These include everything from the highly toxic pentachlorophenol
to the relatively innocuous polyethylene glycol
(PEG) and denatured alcohol . Other chemicals often used
in domestic wood processing are potassium dichromate, ethyl
triethanol amine , glycol humectant, naphthenic acid , copper
hydrate and zinc naphthenate. Standard threshold limit
values (TLV ‘s) based on current medical knowledge have
been established for many of these chemicals, with the intention
of protecting people whose jobs expose them constantly
to these substances. But many chemicals banned in
this country are routinely used by foreign loggers and shipping
companies to prevent insect infestation , mold growth
and dry rot in transit.
It is almost impossible for a woodworker to ascertain which
additives have been used . Michael McCan n , an industrial hygienist
and chemist with the Center for Occupational Hazards in New York City, says, “The best procedure to follow is to
assume that the wood being used has been processed with
dangerous chemicals and take the necessary precautions. It is
also important to remember that it is not uncommon for
woodworkers to toil 1 2 or more hours a day for weeks on end
when preparing for a show or fair, or j ust plain getting caught
up with a work order. Under these conditions , it becomes
doubtful that established ny’s for an eight-hour work day
are applicable . ”
Dr. Bertram W . Carnow, professor of occupational and environmental
medicine at the University of Illinois, points out
that the key factor in determining toxic levels for an individual
is what he calls ” total body burden ” -the sum that each
person ‘ s metabolism and general health will accommodate.
” Liquid or solid particles such as fumes or vapors in aerosol
form , cigarette smoke and other exposures in addition to
those from materials used at work all contribute to the burden
on the lungs, skin and other organs, and should be minimized
, ” says Dr. Carnow.
Many skin irritations are caused by contact with adhesives
and solvents that dry the skin and make it more subject to infection
. In addition , fumes from such chemicals often are not
only toxic if inhaled or swallowed , but also highly flammable.
Epoxies, for example , can cause severe blistering and
scaling. Liquid, uncured epoxy resin and hardener will cause
adverse reactions in more than 40 % of all workers who come
in contact with it . Synthetic adhesives , such as urea-formalde  hyde and phenol-formaldehyde resin , are other irritants with
which woodworkers commonly come in contact . Although
few woodworkers have occasion to use uncured formaldehyde
or phenol resins, they should be aware that “thermal degradatio
n ” of these compounds has been reported when heat
produced during high-speed machining of wood breaks down
glues into separate components, or produces entirely new
compounds .

Toxic Woods
This list includes woods that are known to cause allergic,
tOxic , infectious or respiratOry reactions. Although researchers
point our that not everyone is sensitive to these woods , they
warn that woodworkers should be particularly cautious when
sanding or milling them . The category “respiratOry ailments”
includes btOnchial disorders, asthma, rhinitis and mucosal
irritations ; “skin and eye allergies” includes contact dermatitis,
conjunctivitis, itching and rashes.
• Arbor vitae (Thuja standishii )
• Ayan (Distemonanthus benthamianus)
-So N. W.
• Blackwood , African (Dalbergia melanoxylo n)
• • Boxwood , Knysna (Gonioma kamassi)
• Cashew (A nacardium occide r/tale)
• • Cedar , Western red (Thuja plicata)
• Coco bolo (Dalbergia re tusa)
• Cocus (Brya eben us)
• Dahoma (Piptadeniastrum afr ican lim)
• • Ebony (Diospyros)
• • Greenheart (Oeotea rodiaei)
• Guarea (Guarea thompsonii)
• • Ipe [Iapacho] (Tabebuia ip e)
• • Iroko (Chlorophora exeelsa)
• KatOn (Sandorie um indicum)
• • Mahogany , African (Khaya ivorensis)
• Mahogany, American (Swietenia 1llaerophylla)
• • Makore (Tieg hem ella heckelii )
• • Mansonia (Mansonia altissima)
• • Obeche (Triplo ehiton se/eroxylo n)
• • Opepe (Nalle/ea tnilesii)
• • Peroba rosa (A sp idosperma peroba)
• • Peroba, white (Paratecoma peroba)
• Ramin (Gonystylus bancanus)
• Rosewood, Brazilian (Dalbergia nigra)
• Rosewood , East Indian (Dalbergia la tlfolia)
• Satinwood, Ceylon (Ch/oroxylon swietenia)
• Satinwood, West Indian (Fagara /la ·va)
• Sequoia Redwood (Sequoia se1llpervirens)
• Sneezewood (Ptaeroxylo n obliquum)
• Stavewood (Dysoxylu1ll muelleri )
• Sucupira (Bo wdichia nitida )
• Teak (Teetona grandts)
• • Wenge (Mille ttia la urentii)
This information has been taken ft Om :
National Institute of Occupational Safety and Health
International Labor Organization Encyclopedia of Occupational
Safe ty and Health
Sculpture in Wood by Jack C. Rich, Da Capo Press, New
York , 1977.
“Toxic Woods” by Brian Woods and C. D. Calnan , British
Journal of Dermatology , Vol. 95 , Supplement 13, 1976 (an
excellent source on skin reactions to woo ds, with case histOries
and an inclusive list of toxic species) .

Vibration disease
Another woodworking hazard, well-defined over the years
by occupational health specialists, is a disease that develops
and spreads slowly through the muscles and circulatory system
of the fingers , hands and forearms . Vibration disease is closely
related to an affliction known as Raynaud ‘ s phenomenon,
and is triggered by lengthy use of machinery that vibrates in
the 40 to 3 , 000 cycle-per-second frequency range .
Most woodworkers have experienced a rhythmic tingling in
the hands and arms after using such vibrating tools as orbital
sanders, chain saws and pneumatic chisels. In most cases, the
spasms disappear within an hour. Now, recent medical research
among lumbermen in Canada has shown that serious
side effects of this reaction may develop , although the process
may take from several months to ten years . Smoking and cold
weather tend to hasten the onset of the problem . In some
cases , tendonitis of the elbow and shoulder may set in. Eventually,
numbness and a heightened sensitivity to cold and
humidity will occur, and the fingers and palms of the hands
will become extremely pale-giving the condition its more
common name of “white hand” or ” dead fingers . ” In a few
extreme cases , it has been necessary to amputate the fingers.
” We know that vibrations may cause definite lesions to the
hands with serious potential consequences , ” says Dr. Gilles
Laroche, a cardiovascular surgeon with the Hotel-Dieu Hospital
in Quebec City , in the March 7 , 1 9 7 7 , issue of the Canadian
periodical Maclean ‘s. ” Once severe occlusive arterial
disease is established , the condition is permanent and little or
no improvement will result from cessation of work. In fact ,
the condition may worsen in a large proportion o f patients . ”
Safety experts advise that cutting down on extensive use of
vibrating tools is the best way to prevent this conditio n ,
although some authorities have urged tool manufacturers to
build shock absorbers into vibrating equipment. Many chain
saws now have rubber bumpers between the engine and the
handles, and users report them nearly vibration-free. OSHA
has not set a vibration standard for tools.

Noise
High levels of noise have long been recognized by industrial
safety technicians as unsafe to workers . In a typical wood
shop, decibel levels often exceed industry limits and may
cause hearing loss.
One study cited by NIOSH found that nearly one shop
worker in four had suffered some pemanent damage to hearing
because of high noise levels from operating machinery .
Other studies have found that excessive noise can also contribute
to heart problems and gastrointestinal disorders.
Noise levels are measured in decibels (dB) on a logarithmic
scale on which every increase of 10 dB means a tenfold increase
in noise intensity. Ordinary conversation averages
about 60 dB.
OSHA has set a maximum permissible average noise level of 90 dB per eight-hour working day . The permissible noise exposure rises to a maximum of 1 1 5 dB , a level that can be
tolerated for only 1 5 minutes or less per day. A circular saw
produces between 1 00 and 1 09 dB , a medium-sized woodworking
shop in full operation averages about 1 1 0 dB , and a
chain saw may peak at 1 30 dB . One report cited by NIOSH
states that ‘ ‘ operators of saws, planers, routers, molding machines
, shapers, jointers and sanders are exposed to average
overall sound-pressure levels that exceed 95 dB . For several of
these operations , the average may be as high as 1 1 5 dB . ”
Protection from noise involves damping machinery with
mufflers and sound-absorbing material , keeping machines in
good repair and well-oiled, and mounting machines on rubber
bases to reduce vibration and rattling. In addition ,
OSHA-approved ear muffs and ear plugs-rather than improvised
cotton or wax devices-are recommended . In
general , industrial hygienists recommend ear muffs as the
most effective sound reducer.

Fire hazards
Although most woodworkers are extremely cautious when
using flammable materials, the danger persists. The National
Fire Protection Association reports that the combination of
machinery, wood , volatile fumes and finely dispersed dust in
woodworking shops results in scores of fires and explosions
annually. Small grains of wood dust , when scattered throughout
a confined area, can explode with tremendous force if ignited
by a spark or match . If flammable solvents are present ,
the hazard becomes much greater .
Fire prevention authorities agree that the best way to curb
the possibility of fire is adequate ventilation. If dust and
fumes are vented by a vacuum or “cyclone” air cleaner, and
fresh air is continually available , most fire hazards will be
sharply reduced.

 

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