Painting & drawing blog
ARE SOME PAINTS POISONOUS?
Exploring the toxicity of paint pigments, binders and spirits
Health and Safety is rarely an exciting topic, but there are some fairly jaw-dropping stories about the dangerous effects of the paints used by artists in previous centuries. Lead white paint is thought to have poisoned artists from Michelangelo to Van Gogh, whilst the infamous, arsenic-containing Scheele’s Green which was so poisonous it was apparently deployed to kill rats in Parisian sewers and may have played a part in the death of Napoleon after it was used to paint his walls! It appears that painting was once a genuinely hazardous occupation.
Detail from Wheat Field Behind Saint-Paul Hospital with a Reaper by Vincent Van Gogh, 1889
CC0 1.0 Public Domain. Photo credit: Museum Folkwang
Before the availability of paint tubes painters had to grind pigments themselves or purchase them in powdered form, creating the conditions for toxic pigments to be inhaled. For centuries contemporary commentators observed a set of mysterious symptoms affecting painters in both mind and body which came to be known as ‘Painter’s Colic’. We now recognise these symptoms as having largely been the effects of lead poisoning.
Although by the mid-nineteenth century lead paint was coming under suspicion as the cause of the malady, it would be years more before lead was was fully abandoned in favour of other white pigments such as titanium and zinc. Poor Van Gogh was obviously none the wiser: he used both Lead White and Chrome Yellow (lead chromate) colours frequently and apparently had a habit of licking his brushes.
Whether the effects of lead poisoning could have caused the mental deterioration that culminated in Van Gogh’s suicide is something that can only be speculated about today. Certainly the potentially lethal toxicity of lead is now fully acknowledged and paint made from lead is now banned in most places in the world as a house paint, although exemptions allow it to be sold as an artist’s colour. In the EU however it must be sold in child-proof containers rather than a tube and kept behind the counter.
Although many paint colours are still made from pigments derived from other heavy metals (including cadmium, chromium, cobalt, copper, lead, manganese and zinc) I had always assumed that these would be safe to use provided I didn’t lick my brushes, because the pigments are not handled in the form of a powder or a spray that can be inhaled. Instead we purchase them within a tube and suspended in a medium – usually linseed or safflower for oil paint, a polymer emulsion for acrylics and gum arabic or a synthetic binder for watercolours.
I reasoned that if there were real health considerations with these inorganic pigments, they would be sold under similar restrictions to lead white, or not sold at all. However I did pause for thought when I read about the controversy that raged recently over the EU’s consideration of a proposal to ban all paint made from cadmium, and I also noticed that some of my paint tubes carried warnings intended for the US market, such as the admonishment that cadmium was ‘known to cause cancer by means of inhalation’. However I really couldn’t imagine how I could inhale a dangerous amount of cadmium fumes from a tiny bit of liquid watercolour paint.
My tube of cadmium yellow watercolour paint with a scary warning in the back
It was only when I was expecting my son that I really began to wonder whether my oil paints and the solvents I used to thin and clean up after them were completely safe. Looking back I wonder why it didn’t concern me more that I’d always get a headache when using artists’ white spirit in an unventilated room!
When I looked into the question, I found that whilst information on the health effects of solvents used to dilute oil paint is fairly compelling, hard data on the specific effects of different paint pigments is nearly impossible to acquire. This is because the only research that has been done concerns people handling them within factories or mines who are exposed to much larger doses via airborne exposure of pure pigment particles.
So what exactly is the risk from these traditional heavy-metal pigments which still form a considerable part of an artist’s palette? And in the case of oil painting where the paint is traditionally diluted and cleaned with solvent-based spirits rather than water, should these substances should be avoided and what are the alternatives?
THE SAFETY OF PAINT PIGMENTS
What does your paint actually contain?
Trying to work out what is actually in your tube of paint isn’t straightforward. Manufacturers choose a marketing name for each paint colour they produce, which does not tell you which pigment or pigments are actually contained within it. It’s easy to assume that the colour name on a paint tube and the name of the pigment inside are one and the same, but this is often not the case.
Paint companies will also frequently will name a paint shade after an old pigment that’s now become more or less obsolete due to lightfastness or toxicity concerns, even when the actual pigment used to approximate the old colour is totally different.
A good example of this is vermilion. Vermilion paint was originally made from a mercuric mineral called cinnebar, and later from a synthetically created mercuric sulphide compound. They are both toxic and as a result true vermilion is now rarely sold, although the Michael Harding company does still produce vermilion paint from the original Chinese cinnebar, complete with cautionary warnings about its potentially toxic effects.
Many other paint companies sell a colour they call ‘Vermilion’ but none of these is likely to contain cinnebar or synthetic mercury. Instead manufacturers approximate a vermilion-like colour by substituting one or more different pigments. When a manufacturer imitates a historical single-pigment colour in this way the result is known as a ‘hue’ colour, and they are supposed to label the paint as such.
For example, Winsor & Newton sell a ‘Vermilion Hue’ colour within their Winton oil paint range. This is correctly labelled as the colour contains no true vermilion, but is instead made from a mix of three different pigments. Other companies however fail to include the ‘hue’ description. Royal Talens’ ‘Van Gogh’ range includes a colour that they call ‘Vermilion’ but which is actually made from pyrazolone orange and lithol rubine. Old Holland’s ‘Vermilion’ is really pyrazolo-quinazolone scarlet. I think it’s fairly obvious why Old Holland don’t think ‘pyrazolo-quinazolone scarlet’ is a useful marketing name: it doesn’t exactly trip off the tongue! But you can see how difficult it is even to identify which paint brands contain potentially toxic pigments.
The only place you’ll be able to find out which pigment any paint colour is made from is through a tiny code starting with the letter P (for ‘pigment’) which will be printed somewhere on the tube (you can also usually find a list of pigment codes on the manufacturer’s website). The code for true synthetic vermilion – for example – is ‘PR106’.
This code relates to a universal naming system regulated jointly by the British-based Society of Dyers and Colourists and the American Association of Textile Chemists and Colorists. It allocates every pigment with both a code and an official pigment name. Although these associations advise that best practise would be for the manufacturer to print the full name of the pigment as well as the index code, in reality this doesn’t often happen and only a small minority of brands (like these top quality Michael Harding oil paints for example) will clearly write both pigment names and index numbers on the tube.
Having located your pigment number/s you can use this website to look them up and find out which pigments are in your paint and what source they are derived from. Orange colours will begin with ‘PO’, reds with ‘PR’, greens with ‘PG’, and so on. Natural organic pigments start with ‘N’ rather than ‘P’.
In both Europe and the USA paints must conform to standardized labeling systems alerting the consumer to any health or environmental hazards contained within. In the EU, they must conform to a regulation known as the ‘CLP’ which requires any ‘hazards’ to be indicated on packaging with a warning sign like one of these diamond shaped pictograms. You can find an explanation of the full meaning of these signs here.
The exclamation mark sign is a ‘warning’ mark which alerts you of a hazard to health if the paint is swallowed. It also warns that the product may cause eye, skin or respiratory irritation.
The sign with the figure indicates a ‘danger’ and lets you know that the hazardous content may be a carcinogen or might damage fertility. It may also cause breathing difficulties, organ damage or damage to an unborn child and may also be fatal if aspirated.
In fact, you’re much more likely to see either of these health-related warnings on a solvent-containing product such as white spirit than on a paint tube, although I have noticed the CLP ‘environmental hazard’ pictogram on a tube of Zinc White paint.
On the back of tubes of paint in both the US and Europe you’ll commonly find a little black seal relating to the American ‘ACMI’ (Art & Creative Materials Institute) and inside this seal will be either a large ‘AP’ (Approved Product’) or ‘CL’ (Cautionary Labeling). The ‘Approved Product’ designation certifies that the paint is non-toxic to both children and adults. If there’s a CL label instead then in the label will also contain a specific written warning. This warning is likely to be that the paint may be harmful if swallowed.
Underneath the seals above you’ll notice a statement that the paint ‘Conforms to ASTM D 4236’. This relates to the American Society for Testing and Materials’ ‘Standard Practice for labelling Art Materials for Chronic Health Hazards’ which is a set of voluntary but universally adopted guidelines regarding health and safety labelling. It will typically be declared on every paint tube that might be sold in America, whether produced by a US manufacturer or one based elsewhere.
This declaration doesn’t mean that the paint necessarily poses any health hazard, it just means that any hazard will be clearly listed on the label. If there is considered to be a hazard, this will be stated in written form (for example ‘Do not spray apply’). Finally, you may also see statements that conform to California’s strict regulatory laws such as ‘This product contains cadmium, a chemical known to the State of California to cause cancer by means of inhalation’
The evidence for heavy metal toxicity in paint
It’s noticeable that US regulatory bodies will give warnings about heavy metallic pigments that European ones often don’t seem to consider necessary, making it hard for the consumer to know how seriously to take concerns over various pigments.
With white paint made from lead the health concerns are universal and have long been accepted. You’re not likely to buy lead paint by accident and most companies stick to safer white pigments like titanium and zinc.
Vermilion too has also been more or less phased out due to both toxicity and cost concerns, with Michael Harding being the only UK manufacturer I can find using true vermilion pigment. It’s still hard to assess whether there was any real risk to painters from long term use of vermilion. There’s no doubt that the cinnebar mineral was responsible for the deaths of many who mined for it in centuries gone by and who inhaled a large quantity of it in powered form and and suffered from mercury poisoning as a result.
However this is very different to using the pigment suspended within an oil or acrylic medium, and there’s no data I can find showing that modern vermilion paint has ever caused adverse health effects. It simply hasn’t been studied or tested and so there’s no way to know. Similarly although there is evidence that potters using powdered cobalt may have suffered from cobalt poisoning, there’s no evidence that painting with cobalt paint has ever caused an artist to experience poisoning from the pigment.
Both cobalt and cadmium paints are still commonly sold, although some Japanese and American producers actively avoid them because of health concerns. For example Daniel Smith paints contain only cadmium ‘hues’. In the UK, Winsor & Newton have rechristened the Cadmium hue colours within their professional oil painting range as ‘Cadmium-free’. However they continue to sell the true cadmium paints alongside the hues for those who want to buy them.
As for the EU discussion over cadmium safety, the proposal was originally raised by Sweden out of concerns that cadmium was entering the water supply via artists rinsing their brushes in the sink. The idea that there are enough artists using pure, expensive cadmium paint to cause more than a trace amount of cadmium in water seemed improbable, especially when compared to the amount leaking from discarded nickel cadmium batteries. Sure enough after several years of discussion, the EU rejected the proposal to ban cadmium from artists’ paint.
On the subject of the risk posed by cadmium Winsor & Newton note that ‘The level of soluble cadmium in the pigments is so low that no hazard warnings are needed and they pose no greater risk after swallowing or breathing in than other pigment types. Cadmium pigments are restricted for certain applications but this restriction does not apply to artists’ colours’.
The debate will likely continue. Some artists are concerned that it’s precisely the complete lack of testing or available studies that mean we should play it safe and avoid certain pigments when there are other alternatives on offer. Others take the view that the stringent labelling on products intended for the US market is driven by the greater degree of litigation on that side of the Atlantic and that the warnings are a cover-all for very unlikely events such as a child getting hold of and consuming a large quantity of paint.
As Bruce MacEvoy points out: “ASTM guidelines require paints to be labeled toxic, or potential health hazards, if “in the opinion of a toxicologist” the pigment in the paint might produce “a chronic adverse health effect” as a result of any “reasonable foreseeable use or misuse” of the paints.” However as he further points out these guidelines do not state what would qualify as a chronic health effect, and precisely how this might be tested for by a toxicologist.
What about other pigment sources?
Not all paints use pigments from these inorganic mineral sources of course. Synthetic organic pigments (those ones with names that do not trip off the tongue, like pyrazolo-quinazolone!) have been studied only in a very limited way and long term exposure to them in tube paint form has certainly not been examined. However they are not known to have any adverse health effects.
Common sense advice
Winsor & Newton’s general health and safety information page contains the following disclaimer:
“Winsor & Newton Artists’ Materials do not present any major hazard when used with care and common sense. It should, however, be emphasised that as with other chemical products, high standards of general hygiene should be adhered to, both during and after use of these products and warnings given on individual products should be followed. Prolonged contact with the skin and ingestion (or swallowing) of the product should be avoided. This includes avoiding practices such as applying colour with the fingers or pointing brushes in the mouth.”
Following these sensible guidelines out of an abundance of caution I’m personally happy to continue to use any easily available paint colour. With some of them I wouldn’t handle raw pigment in powder form to mix my own paints, but I think that with tube paint any health risks are probably dwarfed by those posed by the many chemicals people use around the house such as harsh cleaners, house paints, new synthetic carpets and so on. For pregnant women who naturally feel worried about taking any risks, wearing gloves and working with the window open may alleviate concern.
SPIRITS USED FOR OIL PAINTING
It’s generally acknowledged that when it comes to health and safety in painting, the paints themselves are not really the problem. The pigments are not going to harm you unless in pure powdered form, and with oil painting the linseed, safflower, poppy or walnut oils that they are safely bound with are absolutely harmless. However there is quite a significant health problem posed by oil painting, and it concerns the solvents that you use to dilute your paint and clean your brushes, palette and hands afterwards.
Because oil paints however are insoluble in water they can only be thinned or removed by some type of solvent, or some type of oil. The traditional way to work in oil paint is to paint underlayers thinned largely with a solvent like white spirit and then to add increasing amounts of oil to every subsequent layer. This method obeys the ‘fat over lean’ rule of oil painting whereby you avoid a large oil content in your underlayers.
Some people avoid the use of solvents by adding only extra oil to thin their paint. The problem with this is that you can’t so easily achieve the thin, matte washes of colour typical of an underlayer, and have to be very careful to still observe the fat over lean rule so that your upper layers don’t crack as they dry.
Photo credit: jacksonsart.com
The problem with turps and white spirit
Whilst oil dries slowly via a process of oxidisation, solvents evaporate quickly and release toxins into the air. For centuries, turpentine was the traditional solvent used by artists to thin their oil paint. Turpentine is a solvent obtained by distilling resin from living trees and like all solvents it emits Volatile Organic Compounds (VOCs) as it dries. Turpentine is still available and some artists still prefer it for diluting their paint, but there’s no question that it can cause negative health effects including skin and eye irritation, nausea and headaches with quite a small amount of exposure. Long-term, large scale exposure has been quite convincingly linked to organ damage and neurological damage as well as an increased cancer risk.
Now that turps have fallen out of favour most painters use ‘artists’ white spirit’ which is a purified version of the regular white spirit used around the home. White spirit use also frequently causes headaches and nausea. In terms of long term adverse health effects, very lengthy usage (13 years plus of continuous and significant exposure) has been associated with chronic nervous system effects whilst white spirit has also been implicated in Chronic Toxic Encephalopathy amongst house painters. Legal limits are set by most countries for a level of exposure to white spirit of 8 hours per work day. Personally speaking white spirit always gives me a headache if I’m working in an unventilated room, and even if my exposure is much less than 8 hours every a day I just don’t think that this can be a good thing.
How to minimize your exposure when working with spirits
- Always ventilate the room you are working in. When painting with solvents I keep the window open except on very cold days, in which case I employ an air filter unit called an ‘Airbubbl’ made by Airlabs which filters out a lot of the VOCs from the air and removes much of the smell.
- Keep your spirits either in the container that they came in, or in a glass jar. I don’t pour them into anything else because I can’t be sure that the solvent couldn’t break it down.
- Keep a lid on your jar of solvents when you can, and always cover it overnight.
- Don’t paint in the room that you sleep in.
- Wash your hands well if you get solvents on your skin.
Odorless mineral spirits (OMS) and citrus-derived turpentine
To avoid the unpleasant smell of solvents there are a number of odorless or low-odor products such as ‘Sansodor’, a slow-evaporating, product made by Winsor & Newton which can be substituted for mineral spirits. It’s important to be clear that Sansodor is still a solvent-based product, and is classified with the H304 warning: ‘May be fatal if swallowed and enters airways.’
Whether it’s really significantly better for your health than white spirit just because it evaporates more slowly is unclear, and Winsor & Newton does not make this specific claim. However it’s much more pleasant to work with however as it barely smells and I find that it doesn’t give me headaches. ‘Gamsol’ made by Gamblin is another option. Gamblin claims that ‘Gamsol is a petroleum distillate but all the aromatic solvents have been refined out of it, less than .005% remains. Aromatic solvents are the most harmful types of petroleum solvents’.
Photo credit: jacksonsart.com
Recently a number of solvents made from citrus plants have come onto the market, including ‘Zest-it’ solvent made by J and T Blackman and ‘Citrus Turpentine’ made by Wallace Seymour. Citrus based solvents are closer to turpentine than the petroleum based white spirit and are low-odor and supposedly less toxic. They can be used for thinning oil paint as well as as cleaning it.
Another product worth considering is Winsor & Newton’s popular ‘Liquin’ range. These are mediums designed for diluting paint which are more viscose than spirits, but not as glossy as oils. Liquin does still contain solvents but as with Sansador and Gamsol they are slower to evaporate and their aromatic particles have been largely removed.
Any medium or solvent you add to your paint may cause a slight yellowing and may change the consistency of your paint, so you may have to experiment with these various products until you find one that you like.
Oil painting without any solvents
If you really want to avoid any solvent-containing products when oil painting, there are a few ways that you can do this.
- As mentioned, some people use oil (commonly walnut oil) to thin their paint for the lower layers. As long as each layer you apply has MORE oil than the first one, this will still obey the ‘fat over lean’ edict and your painting shouldn’t crack as it dries. You can read about the fat over lean rule in this article on oil painting techniques. It might help to allow as long as possible for your under layer to dry before painting on top.
- Another option would be to paint fairly thickly and in one layer (‘alla prima’) because then you’d only need a little additional oil to loosen your paint and it wouldn’t get overly glossy. Alternatively you could also use an impasto medium to extend your paint and help it flow.
- You could switch to water-mixable oil paints. Because water-mixable oils are soluble in water you can thin your lower layers with water instead of spirits, as long as you also add a little oil to prevent the paint becoming over-thinned and ‘unbound’. Water soluble oil paints work either via the inclusion of an additive which allows water molecules to bind with the oil content in the paint, or by modifying a single molecule of that oil binder to allow it to form a solution with water. You can read more here about using water-mixable oil paint.
- You could paint your lower layers in thinned acrylic paint. This is quite a common practice with some artists. So long as you always use oil paint over acrylic and not the other way around, mixing acrylics and oils is fine.
When it comes to cleaning up after an oil painting session, it really is possible to dispense with solvents altogether. Some people use detergent (washing-up liquid) which works quite effectively to remove oil paint from brushes and hands, but this could leave a residue on the brushes that might contaminate future paint applications. It’s also pretty drying on the hands.
The US company General Pencil make two popular products called ‘The Master’s Soap and Brush Cleaner’ and ‘The Master’s Brush Cleaner and Preserver’ which work very well. Their ingredients are a proprietary secret but are non-toxic and vegetable oil-based. Da Vinci also makes a ‘Professional Brush soap’ derived from vegetable oils. Any oil-based product can remove oil paint and a number of olive oil soaps are marketed to artists for brush and hand cleaning. You could also pick up an olive oil soap in a health food store, or use pure walnut oil.
For the serious oil painter who does a lot of brush cleaning, Jacksons make big tubs of ‘Marseille Soap Pellets’ which are made from palm, coconut and soya oils. You mix them with water to create the amount and consistency that you want. It’s also worth mentioning Weber’s ‘Odorless Turpenoid’ products which get great reviews for washing brushes. Turpenoid is an petrolium-based but odorless turpentine substitute containing no harmful aromatic compounds.