CHEMICALS AND WOOD
As we become more separated from ecological processes, it often seems entirely natural and acceptable for us to treat our wood with an array of hazardous chemicals. If we want a timber that will not be eaten by termites, we make it poisonous to termites. If we want an imported rainforest timber free of borer holes, we fumigate it with chemicals. If we want a timber that will not rot, we impregnate it with chemicals. The piece of wood we eventually purchase may have been exposed to a number of chemical treatments before we get to install it in our home. It is this way of thinking and acting that has led to the wide spread use of chemicals in the forest products industry.
In the following sections we examine some of chemical processes most commonly used within the wood products industry. It has not been an easy section to write for, as mere consumers, we have been deliberately excluded from knowing too much about the chemicals used by the wood products industry. The result is that we are forced to rely on the industry to protect us from chemical abuses. We no longer have to care, the industry will (supposedly) care for us.
In researching the section, we quickly found that, in general, the industry seems to know very little about the long term health effects of the chemicals it uses, sometimes in huge volumes. Ignoring these environmental considerations makes the wood products we use cheap, but they are cheap at an environmental cost. Indeed, even where the hazards are well known, as in the case of using wood treatment chemicals that destroy the ozone layer, the industry argues that alternatives are "uneconomic", and is reluctant to make any change. This is how the industry cares for us. Such ways of thinking are truly amazing if we consider the fact that, by not taking any action, we may be irreversibly damaging the capacity of our ecological systems to sustain us.
in the following sections we realise we are largely blowing the whistle in relation to some of the chemicals used in the forest products industry. Resolving the issues we raise will require huge amounts of careful research and determined effort. It will require a major shift in our ways of thinking about wood. For example, we are going to have to learn to consider the cost of dealing with the harmful effects of our use of chemicals as a normal part of the cost of the wood we purchase. In other words, if we want to use chemically treated wood, we will also have to pay for the environmental safeguards. if we do this, natural alternatives, such as growing termite resistant timber species in our plantations, will begin to look like viable investment propositions.
Volatile organic compounds (VOCs) are the organic solvents used to thin or reduce gluey or sticky finishes so as to make them easier to apply. Large amounts of VOCs are used in the wood products industry in Australia, particularly in furniture manufacture where spray equipment is used for adhesive application, moisture proofing, and final coatings. Some wood finishing products may contain a number of different VOCs (e.g., toluene, xylene, methyl ethyl ketone, benzene, etc.) and the exact formulation is confused where brand names are used instead of chemical names. While the degree of hazard these solvents represent varies, as a general rule they should all be regarded as potentially hazardous.
We are concerned about the use of VOCs for two primary reasons. First, many VOCs, such as the chlorinated hydrocarbons, have been linked to ozone destruction, photochemical smog and the greenhouse effect. Second, VOCs can enter our bodies by being inhaled, swallowed, or through direct skin contact. Such exposure has been associated with health problems such as headaches, nausea, weakness, forgetfulness, respiratory irritations, liver damage, dermatitis, sterility, foetal injury, and cancer.
Worksafe Australia (1993) advised that the following common organic solvents are known to cause, or are suspected of causing, cancer:
Benzene
Carbon tetrachloride
Methylene chloride
Epichlorohydrin
Formaldehyde
Perchloroethylene
Most countries are moving to have these and other dangerous VOCs closely controlled. In Australia, we often have no way of knowing if these substances have been used in the wood products we purchase, nor the levels of the materials that continue to be emitted from the product once it is installed in our homes. This lack of information makes the purchase of substitutes, such as waterborne lacquers or oils, a difficult process for the average consumer.
Often alternatives are just as poorly labelled, relying on meaningless statements such as "environmentally friendly" instead of clear information. If seeking more information about the use of VOCs, manufacturers are required to issue specific product information in the form of a material safety data sheet (MSDS). This is required to be freely available.
In order to reduce the use of VOCs, we could substitute water based solvents, or we could investigate alternative processes.
One of the most common volatile organic compounds we are likely to encounter when working with wood is formaldehyde. Because its use is so common, we have often been asked by readers whether the formaldehyde used in wood products poses a health risk. This is a difficult question to answer in a short section as any explanation depends on a number of interacting factors operating over the life of the product. We cannot cover every product, thus we will approach the question by explaining what formaldehyde is, where it is used, the possible health effects, and what can be done to minimise our exposure to any hazard.
WHAT IS FORMALDEHYDE?
Formaldehyde is a gas at room temperature and is a contaminant found in elevated concentrations in indoor environments. The gas is emitted from pressed wood products which use formaldehyde adhesives, binders, or wood finishes. The gas may also be emitted from urea formaldehyde insulation, fibreglass products, paper products, paints, exhaust fumes from engines without catalytic converters, open fireplaces, cigarette smoke, carpeting, and from a wide range of consumer products where formaldehyde is used as a preservative (WHO 1989).
Pressed wood products containing formaldehyde (e.g., MDF particle board and plywood) find their way into the home or office as kitchen cabinets, shelving, counters, built in wardrobes, bookcases, computer furniture, table tops, flooring, lining, etc.. Most of the pressed wood materials in question have only been relatively recently developed, therefore new buildings, including recently renovated buildings, will typically contain more formaldehyde emitting materials than older buildings.
Formaldehyde has become a health concern to timber consumers primarily because of its increased use glued wood products. As we have already noted, on the one hand, the use of these products is a positive development: it reduces our reliance on solid timber and aids in waste minimisation. On the other handthe high levels of formaldehyde in the air generally correspond to the large formaldehyde releasing surface. areas of these products. In other words, the more glued wood products we use, the more likely high levels of the gas will be found. The higher the level of the gas in the air, the more likely its presence is to be related to adverse health effects. For example, mobile homes and caravans contain a large amount of glued wood product and have been found to have a higher load factor for formaldehyde than conventional homes.
Formaldehyde has always been found in low concentrations in our environment as a consequence of natural processes, Today, however, formaldehyde is produced industrially in huge quantities. As with many new industrial chemicals, consumers are largely put in the position of being guinea pigs in order to determine the safe levels of exposure. It is usually only when complaints start to be lodged that scientists are dispatched to research the possible cause of the complaints. This has been the case with the use of formaldehyde in pressed wood products. The research was prompted by complaints that linked elevated levels of formaldehyde to a wide range of health complaints.
Dr Peter Dingle of Murdoch University has recently reviewed the scientific literature and warns that:
Formaldehyde is a strong respiratory irritant which causes eye, nose and throat irritation, chronic coughing, asthma, shortness of breath, nausea and vomiting, nose bleeds, headaches and dizziness, as well as skin rashes when contact is on the skin. Other health effects associated with formaldehyde ate a prickling irritation of the throat, headache, excessive thirst, tearing and stinging of the eyes. Formaldehyde also has immunological effects causing sensitisation and allergy, with skin being shown definitely to exhibit allergy and the respiratory tract also possibly being affected this way. A number of studies also show that neuro behavioural effects, such as headache, nausea, memory loss, anorexia and psychological changes, occur upon exposure to formaldehyde.
We also know that formaldehyde has been identified by the International Agency for Research on Cancer (IARC) as a Group 2A substance, "probably carcinogenic to humans'. Similarly, Worksafe Australia has classed formaldehyde as a Category 2 substance, a "probable human carcinogen". Given such warnings, most experts agree that it is prudent to minimise our exposure to formaldehyde.
Perhaps the greatest barrier to minimising exposure to formaldehyde in Australia is the absence of information on emissions for the buyer at the point of sale. While regulations to control the emissions of formaldehyde from wood based products have been introduced overseas, Australia lags behind. In some countries, consumers are notified whether the product they are considering contains formaldehyde and, if it does, whether the amount is within agreed safe limits. In Australia, we have no way of knowing and must trust the industry to self regulate.
Given the wide spread use of formaldehyde in pressed wood products, and a reliance on industry self regulation, the issue of what is a safe amount of formaldehyde to be exposed to is highly contentious and problematic. For example, in Australia the guideline is 100 ppb (parts per billion), the World Health Organization has set a guideline of 82 ppb, while Canada and California have set a guideline of 50 ppb (Godish et al. 1995).
The matter is further complicated by the fact that exposure to formaldehyde mainly occurs when the_ product is first installed. The release of formaldehyde from pressed wood products and other sources is known to decrease exponentially with time, with maximum formaldehyde offgassing in the first months to the first year. Research has found that formaldehyde levels are reduced by approximately half within the first three weeks when the product is installed in a well ventilated area.
It would appear from our review that there are three main options to avoid the harmful effects of exposure to formaldehyde.
Third, make best use
of ventilation. Indoor ventilation is the main agent for the reduction
of formaldehyde levels. if we suspect our newly constructed or renovated
home contains materials containing formaldehyde, open the windows and
get some air through. Consider not moving in until the building has been
thoroughly ventilated. Similarly, if working in an area where formaldehyde
is used, or where formaldehyde offgassing materials are stored in large
quantities, ensure proper ventilation and minimise direct exposure to
gas fumes.
Subterranean termites cause most of the termite damage to timber in Australia (French 1991). The most commonly used protection from subterranean termites has been a soil chemical barrier (e.g., aldrin, dieldrin, chlordane or heptachlor). There is widespread concern that the use of such termiticides contaminates the environment, and may harm species other than the targeted termites (French 1994).
Concerns over the use of toxic, persistent chemicals, such as the organochlorines, has led to many of the chemicals used being banned, leaving the pest control industry reliant on a handful of chemical treatments. This situation illustrates some of the dangers and limitations inherent in chemically based approaches to timber use.
Some thought as to how to protect timber without the use of chemical barriers has lead the CSIRO to develop a non toxic product called Granitgard. The use of this product avoids the need to spray dangerous residual poisons under buildings. Granitgard is like a gravel and forms a non toxic barrier to protect slab, strip footing and stumps. The particles of the product are too small for the, termites to crawl through, too heavy and too large for them to carry, and too hard for them to chew.
Thinking like a termite led the CSIRO to an interesting solution. There are many other ways to avoid the need for dangerous chemical treatments for termite control. For example, another barrier method is TermiMesh, a flexible stainless steel mesh which termites cannot penetrate. For a good reference, Robert Verkerk (1990) has written a book called Building Out Termites. In this book the author explains how to build termite resistant buildings, how to modify existing buildings to make them less likely to be attacked, and how to conduct systematic inspection routines.
Methyl bromide is used in Australia to fumigate imported or exported logs, timber, wood chips and a variety of other wooden products. The fumigation is required under international quarantine regulations and may be carried out as part of a routine system, or may be ordered as the result of the detection of pests. Forest products are fumigated to restrict the spread of these pests and to prevent damage to the wood product itself. Treatments are carried out under tarpaulins, in the holds of ships, or in containers (i.e., under circumstance far from 'air tight').
Methyl bromide was listed as an ozone depleting substance by the Fourth Meeting of the Parties to the Montreal Protocol on Substances that Deplete the Ozone Layer (UNEP 1994). This means that, owing to the serious environmental concerns surrounding the use of methyl bromide, Australians should make every effort to reduce emissions of, and to recover, recycle and reclaim, methyl bromide.
Despite a wide variety of substitute, processes being available, methyl bromide is still extensively used in Australia. As a result, large quantities of methyl bromide are still being released into the atmosphere. Indeed, the 'enclosed space" fumigation of timber has been estimated to result in up to 88 per cent of the methyl bromide used being released into the atmosphere (UNEP 1994). This unacceptably high discharge rate occurs because methyl bromide is absorbed by woody materials during fumigation and then released over time. Other significant discharges occur owing to leaks and intentional venting (UNEP 1994).
Our actions in respect to the fumigation of wood may be contributing to the worsening of ozone depletion and the greenhouse effect. We can avoid participating in this process by choosing wood products that are grown locally. If we maintain the health of our local bioregions and use them for wood production, there will be less need to fumigate our wood. Those working with methyl bromide should keep in mind that the National Occupational Health and Safety Commission has listed it as being hazardous. The inhalation of a concentration of methyl bromide above 100 parts per million *can be fatal" (Occupational Safety and Health Service 1992).
PRESERVATIVE TREATMENTS FOR WOOD
Some timbers are subject to attack by insects and termites and may decay owing to the action of fungi or certain micro organisms. This is especially the case in hot and humid climates, or whenever timber comes into contact with the ground. To overcome these problems a preservative treatment for the timber might be considered. Recent service tests conducted by CSIRO have indicated that treated pine is performing better in ground contact than the most durable hardwood.
There are six main groups of preservatives on the market: creosotes, CCAs, light organic solvent preservatives (LOSPs), brush on coatings, ACQ and a new product called copper azole preservative.
Creosote is a heavy duty timber preservative, traditionally used in industrial applications such as bridge and wharf timbers, electricity poles, railway sleepers and marine pilings. The traditional creosote treatment gave timber a black, oily appearance and a strong tar based odour. This vapour could irritate the eyes and skin.
A new creosote treatment, known as PEC creosote (pigment emulsified creosote), has recently been developed jointly by CSIRO and Koppers. PEC creosote retains the advantages of traditional creosote but, in addition, it is dry to touch, more resistant to leaching out of the timber, and releases less vapour. It is light brown in colour rather than black.
Creosote typically contains over 150 chemicals, some of which are known carcinogens (Occupational Safety and Health Service 1992). Creosote products are banned for domestic use in the United States of America because of suspicions about carcinogenicity and birth defects. Given such concerns, workers applying traditional creosote, or the more recent PEC creosote, should take precautions to avoid both long or shortterm exposure. We also note that little information in currently available as to acceptable methods to dispose of creosote treated wood and for these reasons we can not recommend creosote as a eco friendly timber treatment.
The Good Wood and Paper Guide FRIENDS OF THE EARTH 1999