One might think that paint would be a relatively simple subject regarding its environmental credentials; that either it would be toxic, or not – but nothing could be further from the truth.
The OED defines paint as: ‘A liquid which when spread over a surface dries to leave a thin layer of colour or protective coating’, and as such has been used both decoratively and protectively for millennia.
There is no such thing as a natural paint, apart perhaps from ochre. As time has progressed, we have come to expect more and more from our paints than pure ochre can possibly provide, and therefore modern paint has many ingredients and an impact on both the environment during the manufacturing process, and health during application and use. Unused liquid paint is treated as 'hazardous' and requires appropriate disposal.
Most paint is made from three ingredients:
- Pigments provide colour and opacity.
- The Binder, or ‘vehicle’, holds the pigment to the surface and influences gloss and durability.
- Solvents, or ‘diluents’, keep the pigment and binder liquid for application and control viscosity.
Other possible ingredients are biocides to prevent bacterial growth; filler to thicken paint, impart toughness or texture, or reduce the costs; or additives to prevent 'skin' from forming, improve flow to enable easy application, accelerate/retard drying and prevent foaming, improve the finished appearance, improve pigment stability, or impart antifreeze properties. Paint may also include catalysts, thickeners, stabilizers, emulsifiers, texturisers, adhesion promoters, UV stabilizers, and flatteners (de-glossing agents).
Much of the environmental impact of paint comes from the manufacture of these ingredients and additives and not from the production of the final mix. Each additive also has a level of toxicity that it imparts upon the paint.
Paint is applied to a surface wet, whereupon the solvent evaporates, leaving a permanent film of pigment and binder.
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First and foremost, pigments are used to provide permanent colour, but they also help to control opacity and other aspects of the paint’s finish.
Titanium Dioxide (TiO2) is comprehensively used throughout the paint industry - including in 'eco' paints (it replaced previously well-known, very toxic, white pigments such as Lead Oxide). It is particularly popular because it has a very high opacity, and so can easily cover whatever it is painted over. Chalk and lime are less well used due to their very low opacity, meaning many coats have to be applied.
Titanium Dioxide manufacture is responsible for the greatest environmental impact of paint. Manufacture emissions include CO2, N2O, SO2, NOx CH4 and VOCs, and manufacture wastes include spent acid and metal sulphates – a number of EU directives are seeking to reduce and eliminate the pollution caused. It has a high embodied energy, and raw materials are derived from scarce resources.
There are 'natural' and 'man-made' pigments, although 'natural' pigments do not necessarily have lesser impacts than those that are ‘man-made’. Pigments are also either 'organic' or 'inorganic' – which is not the same thing.
As might be imagined, early organic pigments were derived from plants, however most modern organic pigments are synthesised from coal tar and petroleum distillates. Synthetic organic pigments generally have good colour strength, but low opacity.
The earliest paints of all used pigment obtained from minerals in the earth ground to a fine powder – well-known examples being ochre and sienna. Modern inorganic pigments are usually metallic oxides derived from iron and clay, or synthetics produced from petrochemicals.
The environmental impacts associated with coloured pigments are as various as those for Titanium Dioxide, but not as intense. However, most paints rely on titanium dioxide for opacity, no matter their resulting colour.
The binder provides adhesion to the surface, binds the pigment, and gives the paint its durability. Binders are either oil-based or latex-based.
Oil-based paint requires an oil-based binder - both will oxidize or dry when exposed to air, hardening at the same time.
Vegetable-based 'Natural' oil binders include linseed oil, tung oil and soya oil. Modern oil-based paints contain binders based on modified oils called alkyds - made from vegetable oils and synthetic resins, which dry harder and faster than oils.
Latex-based paints don’t actually contain latex - the polymer binder creates a film that resembles natural latex rubber. When applied, the water evaporates, leaving a continuous film of pigment and latex-based binder bound together. Almost all water-based paints have a latex-based binder.
The two most common types of polymers used in latex paint are 'acrylic', most suitable for exterior use, and 'vinyl acrylic', which is mostly applied internally. Other latex binders include styrene-acrylic and terpolymer.
Most modern emulsions are water-based with added latex for durability – the amount of latex added determines the sheen seen in matt, eggshell, silk, or satin finishes.
The solvent is the liquid that suspends the other constituents to enable application. Once the paint is applied, the solvent evaporates, leaving the pigment and binder combined forming a coat of paint.
Solvents are water or organic. 'White spirit', used in alkyds, and 'mineral turpentine', used as a paint thinner and for cleaning brushes, are the most common organic solvents, both derived from petroleum. Other petroleum-based organic solvents include alkanes (isoparaffins), methyl ethyl ketone (MEK), methylated spirits, xylene, toluene and acetone. 'Gum turpentine and 'citrus oil' are examples of solvents used in paint that are not petroleum-based.
Even paints described as 'water-based' will include small quantities of organic solvents to enable enhanced workability.
There are a whole cocktail of potential additives mixed into paint – here are some of the more usual ones:
Biocides are added to prevent in-can bacterial growth as well as fungal growth on the finish. By their very nature, biocides are toxic and their use is tightly controlled by European legislation. Prior to legislation, biocide formulas were relatively simple but likely to be toxic – mercury for example. Post-legislative formulas are more complex.
Many chemicals are available as biocides, some of which continue to concern health campaigners. Obtaining information about specific formulas is usually difficult however, as manufacturers regard the information as being commercially sensitive. This is compounded by paint manufacturers being generally averse to listing the contents of their products.
Surfactants reduce the surface tension of water, allowing for easier painting. Once commonly used in paint, alkyl phenol ethoxylates (APEs) and perfluorinated surfactants have largely been phased out due to proven endocrine disruption and bioaccumulation respectively. A new generation of surfactants has taken their place, which are believed to be far less toxic.
Driers do exactly what you expect them to – they accelerate the drying of organic solvent-based paint (by catalysing oxidation). Driers are mostly metals, including calcium, cerium, cobalt, manganese, and zirconium. There is concern about the possible health impacts of metal driers, with cobalt particularly associated with lung, heart, and allergy problems due to exposure in production, application and use.
Linseed oil paint is known as a 'drying oil', which dries through exposure to the air without the need for solvents. Linseed oil was commonly used before being replaced by modern alkyd resins and other binders, but is enjoying a revival due to its lack of organic solvents.
Linseed oil paint may well be safer than modern oil-based paint, however it’s not without its own impact on health or the environment – it has a high embodied energy and emits Volatile Organic Compounds (VOCs), albeit in very small amounts.
Limewash is composed of slaked lime (calcium hydroxide), combined with a low proportion of an organic binder such as tallow or linseed oil. The oldest true ‘paint’, limewash cures through a reaction with carbon dioxide in the atmosphere and hardens over a few days to form calcium carbonate in the form of calcite (this reaction is known as carbonation), thereby sequestering CO2!
Limewash is not particularly durable, especially in polluted environments where the coating can degrade rapidly, and it must be applied regularly. Limewash can be coloured with earth pigments to produce a small range of colours. It is a natural biocide.
‘Whitewash’ is limewash with chalk added as a filler to make it more economical.
Health hazards are restricted to irritation on the skin, or to the lungs if inhaled during application.
Silicate Mineral Paints are mineral-based, formulated with potassium silicate (‘water glass’) as the binder, combined with inorganic, alkaline-resistant pigments. The paint soaks into the underlying material where the potassium silicate reacts with the material to form an insoluble microcrystalline silicate bond. Secondary crystallisations also take place between the binder, the colour pigment and carbon dioxide in the atmosphere.
Silicate mineral paints are particularly effective for use on render - providing an alternative coating to limewash. Anecdotal evidence from Europe and Scandinavia claim that silicate paint systems can last in excess of 100 years. Silicate paint is generally very low toxic paint, with little environmental impact except embodied energy, which is slight in itself.
Distemper Paint is an early form of whitewash, with a binding element of glue or oil.
'Soft' distemper is a water-based paint comprising a white base pigment such as powdered chalk, bound with gelatine. The basic mix can be tinted with 'lime-fast' pigments to give a wide range of colours, including blues, greens and various earth tones.
The environmental impact of traditional distemper is minimal and limited to the extraction of raw material and the production of pigments. Some modern distempers have replaced the gelatin binder with synthetic glues such as polyvinyl acetate (PVA), effectively making them vinyl emulsions.
'Clay paint’ is an increasingly popular variant of distemper paint, using clay powder rather than chalk. Clay paints boast of their 'natural' or ‘eco’ credentials, however be aware that contents might include PVA (listed as 'vinegar ester') and methyl cellulose ('cellulose binder') as well as other typical additives.
The downside of distemper is that it is easily rubbed off, and its use should be restricted in areas of high traffic such as corridors.
Volatile Organic Compounds have a high vapour pressure at room temperature, which means that they can vaporise into the atmosphere. The presence of VOCs in paint is significant both in terms of environmental impact and health.
Organic solvents used in paint are the main source of VOCs – for example white spirit contains the 'aromatic hydrocarbons' xylene, methyl benzene and ethyl benzene, all of which are VOCs.
VOCs are also emitted from other components such as some pigments and biocides - leading to a degree of variance even amongst brands (and colours) of paint described as low-VOC.
VOCs are emitted both during application and for extended periods afterwards – indeed one study found that only 50% or less of the VOCs in latex paint are emitted in the first year. In fact there have been many studies and papers that have found strong links between paint and ill-health, including one that found that there was a 'strong' link between the use of household paint and leukaemia, almost certainly attributable to VOCs in solvents.
Contracting leukaemia through VOCs in paint is no doubt pretty extreme, however they certainly increase the risk of childhood asthma, and can produce a number of physical problems such as eye and skin irritation, lung and breathing problems, headaches, nausea, muscle weakness and liver and kidney damage.
It’s not just physical effects that have been proven either: 'Organic Solvent Syndrome' refers to temporary mental derangement through prolonged exposure to organic solvents, and has been understood since the nineteenth century. Although largely accepted in Europe, it is still debated in the UK.
Synthetic solvents aren’t the only ones to blame – the 'natural' solvents gum turpentine and citrus oil (Limonene) have been found to be skin, eye, mucous membrane and upper respiratory tract irritants, and may affect the central nervous system, gastrointestinal and urinary tract.
Given the significant levels of VOCs associated with paint and their potentially harmful effects, legislation and labelling have been developed to limit their use.
The EU’s Volatile Organic Compounds in Paints, Varnishes and Vehicle Refinishing Products Regulations (aka VOC 2010 legislation) is the most important and has the greatest impact on the issue. In order to enforce cuts in VOC emissions, the legislation splits paint function into 12 subcategories and assigns each category its own VOC limit.
There is also a voluntary European eco-label which looks to set limits on the following standards:
. Limited Volatile Organic Content (VOC) and Volatile Aromatic Hydrocarbons (VHS)
· Reduced Sulphur emissions during production
· No use of heavy metals and substances harmful for the environment and health
· User instructions for use including storage, waste management and cleaning of tools
· Limits on the emissions and discharges from the production of titanium dioxide pigment
The paint industry has been forthright in its views of this worthy standard - 'On the whole the paint industry does not intend to use this label'. To date, it is understood that only one manufacturer has attained the eco-label.
The B&Q Paint labelling standard attributes 5 labels from 'Minimal' (0-0.29%) VOC content through to 'Very High' (more than 50%), based on grams per litre of any organic compound ingredient having an initial boiling point less than or equal to 250°C measured at a pressure of 101.3 kPa.
Buying paint is tricky, because as much as you may want to avoid all the nasty VOCs, you also need a paint that does the job – otherwise it would be completely unsustainable!
Alas there are some paints, particularly 'eco' paints, on the market that just don't do what they say on the tin. Failures or inadequacies generally occur with outdoor paints, such as poor durability, including fading, poor adhesion, chalking, and yellowing, or low levels of coverage, necessitating several coats – thus increasing the environmental impact.
But also be aware of greenwash - the paint industry is awash with greenwash. Adding 'Eco' as a prefix has become standard on any tin of paint that has less VOCs than the average 20 years ago and unfortunately in terms of paint it is largely meaningless. Even so-called green manufacturers are guilty of marketing 'Zero VOC' paint, which with few exceptions, contains VOCs – however small in quantity. Likewise, ‘Natural’ is no guide to toxicity or environmental impact.
In a nutshell, it is difficult to find paints that are devoid of VOCs and titanium oxide whilst still performing as you require – this is not helped by the paint industry not listing the ingredients of their paint.
It is best to buy water-based paint with a low titanium oxide content together with low quantities of binder, and avoid paints with high levels of organic solvents - which is becoming increasingly easy due to legislation.
Research your paint preference and study the lists of ingredients where available to compare chemicals to databases of toxins - if ingredients are not published, assume a reluctance by the manufacturer to disclose and avoid that paint!
Another option is to consider using paints with a high recycled paint content, such as Newlife Paints.