Common VOCs in paints, primers and varnishes include benzene, formaldehyde, kerosene, ammonia, toluene, and xylene, all of which are known carcinogens and neurotoxins. Exposure to VOCs can irritate your eyes, nose, throat and skin and are proven to increase allergies, asthma, and respiratory problems, central nervous system symptoms (such as headache, rapid heartbeat) and even weaken the immune system. They can also be harmful to the liver and kidneys. In addition, it is now known that it is possible for two or more ‘less harmful’ VOC’s to combine to create a more powerful toxin.
Research last year in the journal Thorax showed that exposure to VOCs increase the risk of childhood asthma. Swedish research published in the Journal of Occupational and Environmental Medicine in 2002 shows that people in the painting trades or who work in paint manufacturing may have an increased risk of various cancers. For men the risk was greater for bladder and lung cancer, for women cancers of the oesophagus, larynx and oral cavity were more common.
In terms of its environmental impact, for every ton of paint produced, the resulting waste can be anything up to 30 tons. Once in the soil or air, this waste can be persistent and toxic.
Household paints contain carrier oils, dispersion agents, viscosity adjusters, thickeners, surface tension adjusters, plasticisers and preservatives and many contain synthetic colours. Some contain antifungal agents such as arsenic disulfide, phenol, formaldehyde, and quaternary ammonium compounds.
Modern emulsions are water-based, with vinyl or acrylic resins added to make them more hardwearing. The amount of resin determines the varying degrees of sheen seen in matt, eggshell, silk and satin finishes. Gloss paints are oilbased and include resins to give them a hardwearing quality.
Acetone: Solvent. Can cause eye, nose and throat irritation, headache, dizziness, dermatitis.
Ammonia: Preservative. Can cause eye, skin and respiratory irritant, and trigger asthma.
Benzene: Solvent. Can cause skin, eye and upper respiratory tract irritation. Neurological symptoms from inhalation include drowsiness, dizziness, headaches, immune system damage, blood disorders; carcinogenic.
Ethylene glycol: Solvent. Can cause central nervous system depression; ingestion causes kidney damage.
Formaldehyde: Preservative. Irritates the eyes, nose and throat; allergic skin reactions; breathing difficulties; carcinogenic.
Methyl alcohol: Solvent. Eye, skin, mucous membrane irritation. Overexposure can provoke headache, drowsiness, nausea, vomiting and blurred vision.
Phenol: Biocide. Can cause mouth, eye, nose and throat irritation; dermatitis, headache, dizziness, muscle ache and pain, tremors and twitches.
Kerosene: Solvent. Can cause eye, skin and respiratory system irritation; dermatitis; anaesthetic; toxic to aquatic life
Ethylene acrylate: Film former, polymer. Can cause irritation to the eyes, respiratory system and skin; potential carcinogen
Propylene glycol: Solvent. Inhalation and skin contact can cause dermatitis with erythema, oedema, and weeping
Quaternary ammonium compounds: Biocide. Can cause skin, eye and nose irritation
Trichloroethylene: Solvent. Central nervous system effects including sleepiness, fatigue, headache, confusion, and feelings of euphoria. Damage to the liver, kidneys, immune and endocrine systems
Vinyl Acetate – Acrylic Copolymer: Film former. Can cause eye, nose and throat irritation, lung damage; convulsions have been observed in rodents inhaling high levels.
Safer alternatives exist. Some contain no chemical solvents, while other, more widely available commercial brands just contain a lower percentage of VOCs than conventional paints. Eco-friendly paints make use of ingredients such as turpentine or d-limonene as alternatives to white spirit. Instead of plastic binders they may use linseed oil and casein and chalk and clay may replace fillers such as titanium dioxide. Colours are often derived from natural earth and mineral pigments.
Additives Affect and Enhance Many Paint Properties
- Thickeners and Rheology Modifiers provide adequate viscosity (thickness) so the paint may be applied properly, and impact how thick the paint goes on and how well it flows out when applied. Modern rheology modifiers help latex paints resist spattering when applied by roller, flow out smoothly, and reduce spoilage (resulting in a putrid odor and/or loss of viscosity).
- Surfactants (specialized soaps) stabilize the paint so it won’t separate or become too thick to use, keep pigments dispersed for maximum gloss and hiding, help “wet” the surface being painted so paint won’t move about during application, and provide compatibility with tinting colorants.
- Biocides, used in latex paints, are available in two types: a preservative to keep bacteria from growing in the paint, and a mildewcide to discourage mildew from growing on the surface of the paint after application.
- Defoamers break bubbles as they are formed in the paint.
- Co-solvents, which are additional liquids other than water, enhance brushing properties, help liquid paint resist damage if frozen, and aid the binder in forming a good film.
Different types and grades of paint provide different application and resistance properties, depending upon the kinds and levels of ingredients used to create the paint. In turn, the properties of a paint determine the general quality of the coating.
Pigments, which are finely ground particles or powders that are dispersed in paints, provide color and hiding; some are used to impart bulk at relatively low cost. There are two primary categories of pigments: prime and extenders. Prime pigments provide whiteness and color, and are the main source of hiding capability. Titanium dioxide (TiO2), the predominant white pigment, provides exceptional whiteness by scattering light; provides whiteness and hiding in flat or glossy paint, whether wet, dry, or rewetted; is relatively expensive; requires the use of an appropriate extender to ensure proper spacing of particles to avoid crowding and loss of hiding; and has more chalking tendency in exterior paints than most color and extender pigments. In contrast, color pigments – either organic or inorganic – provide color by selective absorption of light. Color pigments are compounded into liquid dispersions called colorants, which are added at the point of sale to tint bases, and to white paints designed for tinting. In the factory, color pigments are used as dry powders and in liquid colorant form to make pre-packaged color paints. Extender pigments (also known as “extenders”) provide bulk at relatively low cost. They add much less hiding than TiO2, and impact many properties, including sheen, scrub resistance, exterior color retention, and others. Commonly used extenders include clay, silica and silicates, diatomaceous silica, calcium carbonate, talc, and zinc oxide.
The binder provides adhesion, integrity, and toughness to the dry paint film by binding the pigment together. The binder affects application properties like flow, leveling and film build, and gloss development. Oil-based binders generally refer to both oil and alkyd coatings. Some coatings, particularly exterior primers, are made with combinations of oils and alkyds to achieve appropriate flexibility. Latex-based binders are generally found in most water-based (or latex) paints. Two types of latex binders are most commonly used in North America: 100-percent acrylic and vinyl acrylic (also called PVA, for polyvinyl acetate).
The liquid portion of the paint (also referred to as the “carrier”) provides desired consistency and makes it possible to apply the pigment and binder to the surface being painted. For most oil-based and alkyd paints, the liquid component is paint thinner; the liquid in shellac-based primers/varnishes is denatured alcohol; lacquer thinner is used for clear and pigmented lacquers; and water is primarily used in latex paints.
Pigments and the binder are what are left on a surface when the paint dries and the liquid portion evaporates. Together they are called the solids portion of the paint (pigments + binder = solids). The coating (i.e. paint, stain, primer) consists of the solids and the liquid (solids + liquid = coating). A paint with higher solids content will provide a thicker dry paint film for a given square-footage per gallon, which results in better hiding and durability, compared to a paint with lower solids content.