In the 1990's, people are becoming more concerned about the effects on health and the environment caused by the various building products used in the home and workplace. For example, many will be aware of the allergic (and more serious) responses caused by outgassing of formaldehyde from the the synthetic resins used in composite boards (particle/chip board, plywood, etc), carpets, glues, insulation foams, paints, and cleaning products.
Others will be aware of the intractable wastes and pollution spills associated with the petrochemical (and petroleum) industry - from which most of the organic chemicals used in the manufacture of these building products are derived.
Paint is one such product used by nearly everyone at some time in their life but about which they know very little. This is not surprising because paint containers often display labels which do not disclose any information about their contents, but advise the user to work in 'well ventilated areas' or that the product may be poisonous.
Research conducted overseas, and recently confirmed in Australia 1 has shown that inside the home or office, air pollution can be much greater than on a busy urban street. This has given rise to the term 'sick building syndrome' 2 and those affected by it report a variety of symptoms, including headaches, nose, throat and lung irritation, eye irritation, feelings of disorientation and fatigue. Up to 300 different chemicals may be released from building materials and are thus present in the house or office's atmosphere.
Paints and varnishes are primary contributors to this interior air pollution, with the greatest effects lasting up to two months after application but continuing for periods of up to five years 1. Often do-it-yourself painters may feel sick or suffer headaches from fresh paint, but for those who work with paint for a living, the medical evidence is far more serious. For example, a World Health organisation report 3 released in 1989 revealed that professional painters had a 40 percent higher than normal chance of contracting lung cancer, a higher risk of nervous system disorders, and that female painters were likely to suffer frequent miscarriages. It was also found that painters were more prone to producing children with birth defects, had a higher than average chance of developing brain tumours, cancers of the stomach, lymph gland, larynx, kidney, prostate or liver. Medical journals contain many case studies which support these findings, and when compared with the known and suspected reactions to chemicals found in paints, there are remarkable similarities. More will be said about this later in the article, but first a brief history and update on the industry is required.
Originally, paints were quite simple mixtures of binder (glue), and pigment with a solvent like water sometimes added. Binders such as beeswax, egg yolk, plant gums or flour were mixed with ground pigments of ochres, clay or charcoal to provide paints which were used to decorate caves. The Egyptian and Greek cultures perfected encaustic (wax + pigment) painting which was used to decorate temples and other important buildings. Later, as the the technology of domestic building progressed, lime-washes were much used. Paints required mostly white pigments, and the first strongly opaque white pigment was obtained when methods were found to supply sufficient quantities of lead carbonate. When this was mixed in raw or boiled linseed oil, it became a paint which could be coated onto many different surfaces and this expanded the range of paint applications on buildings. Simple formulas of this kind continued to appear in chemical formulae texts until the 1930's 4. (Australian houses painted prior to to the 1950's are highly likely to contain lead/linseed oil paints.) As the danger of lead contamination became more apparent, paint manufacturers were forced to convert to using zinc oxide, and later titanium dioxide, both of which are non-toxic. During the same period, simple binders like linseed oil were quite quickly replaced by synthetic resins derived from petroleum.
Prior to World War II, painting was still very much an activity resticted to the professional painter and paints were used more sparingly. However, with the advent of plastics technology, abundant petroleum, and the growth of the post-war consumer society, paint companies were able to offer low-cost products and quickly became skilful at developing markets that were previously nonexistent (ie, the home handyman market). Sales and new uses for paint continued to increase and today' world market is worth about $US35 billion. Western Europe, USA, Canada and Japan represent 85 percent of the market, while the rest of the word represents only 15 percent 5. ICI (Imperial Chemical Industries) is currently the world's biggest paint company and in Australia distributes under the trade names Dulux, Berger, Hadrian and British Paints.
Although some rather remarkable technological advances have been made by the paint industry, it would be fair to say that consideration of effects on inhabitants, workers and the environment has not been part of the techno-evolutionary process. The focus has generally been on product durability, economic competitiveness and expansion of the market. Today, paint companies are being forced by governments and consumer pressure to take the environment (both interior and exterior) into consideration. This is seen by some as the 'bane' of the paint industry 5, and in the future, we may see Australian factories moving offshore into South East Asia, where pollution legislation and worker occupational standards are either more lax or nonexistent.
It is very difficult, even for a chemist, to make sense of today's paint formulas 4. Most of the ingredients which may include plasticisers, antifoaming agents, synthetic polymers, fungicides, bactericides, organic solvents, etc, are now identified by trade names which reveal little of their real nature. It is best to resort to surface coating manuals and textbooks 5. The binders now include alkyd resins, vinyl acetate and methyl methacrylate (acrylics), styrene-butadiene resins, urea formaldehyde, melamine formaldehyde (amino resins), epoxy resins and polyurethanes. Of these, the most commonly encountered products contain alkyd resins, acrylics, polyurethanes and epoxy resins: Alkyds are in part made from vegetable oil by an esterification reaction. These are most often used in enamel (oil-based) paints which are thinned with turps.
Acrylics and styrene-butadiene polymers are mainly used in water-based paints for interior and exterior use.
Polyurethane and epoxy resins are mostly used in varnishes and floor finishes. Because of the fact that enamel paints, polyurethane varnishes (organic solvent-based), and epoxy varnishes are not water-soluble, they usually contain some aromatic hydrocarbon solvents like xylene or toluene. Turps, which is often used to thin these products also contains about 25 percent aromatic hydrocarbons. The toxicology of aromatic hydrocarbons has been well studied and the effects on the human body include headache, convulsions, central nervous system damage, respiratory irritation, dizziness, kidney and liver damage, fatigue, hallucinations, dermatitis, carcinogenesis, teratogenesis, and mutagenesis 5. (The complete list is far too long to include here - those interested should consult the references). Paint companies have been directed by governments and medical bodies to move away from using these types of solvents, although products containing them are still quite widely available on hardware shop shelves.
Acrylic water-based or latex finishes are slowly replacing these products since they are considered safer. However, the term 'water-based' is not entirely true, since these paints require co-solvents like ethylene glycol, or a glycol ether substitute to work properly. Glycol ethers are known as teratogens (cause birth defects) and are banned from use in many countries (5, 7). They can still be added to Australian paints. Ethylene glycol causes skeletal malformation in rats, albuminuria, tremors, cyanosis, anuria and the presence of oxalic acid in the urine (6, 8, 9). Apart from solvents, methyl methacrylate may be released from acrylic paints and cause eye and mucous membrane irritation and drowsiness. These are linked with anorexia and are also suspected of causing carcinogenesis and mutagenesis (4).
Polyurethanes are made from isocyanates, the chemicals associated with the world's worst chemical accident in India in 1984 (the Bhopal disaster, which involved the accidental release into the atmosphere of methyl isocyanate from a Union Carbide factory). They cause lung irritation or lung damage and are sensitising chemicals, meaning that after sufficient exposure, one can become highly sensitive in an allergic way, reacting to even very small doses of the chemicals (5, 10). They may released as monomers from both water-based and organic solvent-based polyurethane varnishes. The combination of volatile aromatics and the release of isocyanates makes polyurethanes one of the most hazardous interior-use products on the market. (It is especially important that women in pregnancy avoid the fumes of such products.)
Other materials that paints may contain include organic and inorganic pigments which have varying degrees of toxicity. Cadmium, lead, chrome and nickel-containing pigments may still be added to some paints. In addition, unidentified fungicides, bactericides and algicides may also be present. Zinc chromate which is added to metal primers has now been found to be strongly carcinogenic and will no longer be produced. It is however still available on shop shelves.
Paint companies will argue that in 'well ventilated areas' airborne concentrations are harmless, but often such ventilation is not achievable, particularly in air-conditioned buildings or older buildings with small windows. Another important consideration is that there has been little investigation into the synergistic effects of the range of airborne chemicals which may be present in the interior atmosphere. A final point is that many materials added to paints which were said to be safe originally are now banned. This process continues today.
From the point of view of the greater environment, it must also be considered that these products contain plastic polymers and solvents with very slow rates of biodegradability. (Try putting a dried-out lump of of paint in the compost heap!) Even acrylic paints should not be washed down the drain, for this is an environmentally irresponsible action. Paints and solvents that contain aromatic hydrocarbons are strongly ecotoxic and should not be allowed to enter any water systems.
For those who suffer from chemical sensitivities or who would just prefer to avoid using the conventional products, there may be some good news, in that some alternatives are now available. In Australia, the brand names Livos and Bio Products 11 are becoming better known. These companies, among others, supply a full range of paints and varnishes that are made from renewable resources (natural oils, tree resins, waxes and cellulose) and mineral pigments which, as mentioned earlier, are claimed to be non-toxic and environmentally benign.
1. Peter Dingle, Lecturer in Toxicology and Poisons, Murdoch Uni, WA.
2. Healthy Home & Healthy Office
3. World Health Organisation report
4. The Chemical Formulary
5. Surface Coatings
6. Pesticides and Human Health
7. Regulation of Priority Carcinogens & Reproductive Developmental Toxicants
8. Developmental stages of the CD rat skeleton after maternal exposure to ethylene glycol
9. Biochemical Toxicology of Environmental Agents
10. A Case of Hypersensitivity Pneumonitis due to Isocyanate Exposure
11. See under Non Toxic Paints