Unlike a dye, which is soluble, the pigment is simply suspended in the liquid and gradually falls to the bottom, like sand in the sea. Additives can be added to the dispersion to give it special properties.
Let us discover the composition of these three components.
1. Composition of a colorant dispersion
1.1 Colorant component
This property is entirely due to the pigment, which has colorant properties due to its high concentration of colorant units, or chromophores. The tinting strength of a pigment depends on its chromophore concentration.
Les pigments peuvent être d’origine:
- These pigments are quite rare, since plants mainly produce dyes (chlorophyll, annatto, carotene, achiote, indigo, etc.). Pigments of plant origin are natural.
- Red derived from the murex (a shellfish) was used by the Romans to dye emperors’ togas. Use of the shellfish (protected) is now prohibited. However, carminic acid or carmine, a pigment of animal origin (cochineal), is still used (and permitted by law) in permanent makeup and tattooing products. These are natural organic pigments.
- Mineral (mineral or inorganic pigments). Many of these are metal oxides. They provide better coverage and last longer in the skin than other pigments. Some have a very stable colour (titanium dioxide, chromium oxide, manganese), while others are sensitive to oxidation and can change colour (iron oxides), and others are pH sensitive (ultramarine, Prussian blue). Mineral pigments were synthetic (oxides obtained by induced metal oxidization), but since organic ingredients have become important, they are sourced naturally with increasing frequency (pigments are extracted, obtained by physical means). Mineral pigments can therefore be either natural or synthetic.
- Organic pigments are a recent invention, appearing in the mid-19th century with the development of organic chemistry and the dye industry. They are complex molecules that contain at least one carbon atom. Even carbon black (black pigment CI 77266) is not derived from the ore, but is obtained through the incomplete combustion of organic matter in blast furnaces. Organic pigments are actually quite rare: they are more often dyes (soluble) which are made insoluble through setting with an aluminium oxide lacquer. They offer less coverage than minerals and last less time in the skin. To compensate, they are mixed with other, more stable products (mica, quartz, PMMA), linked in a polymer or combined with mineral pigments such as titanium oxide (white pigment CI 77891). Their colours are stable. Organic pigments are all synthetic, with some exceptions (cochineal, kermes).
1.2 Dispersant component
This can be oil-based (mineral or vegetable oil) but is normally water-based: water, glycerine, propylene glycol, ethyl alcohol or isopropyl alcohol.
- Water does not add to the quality of the product and should be avoided as a dispersant. It may be found in small quantities when a water-based additive (pH modifier) is added.
- Glycol ethers, used as a dispersant, are divided into 2 families: propylene glycols, which can be used, and ethylene glycols, which should not be.
- Glycerine is a biocompatible thickening agent.
- Alcohol, in addition to its disinfectant properties, improves setting in skin. It should be used in small quantities as it is slightly irritating.
- Too numerous to list, they are supposed to add additional properties to the final product.
- Some are prohibited (preservatives, fixing agents), while others are debatable (polymers, ethoxylated derivatives), and others have positive properties: pH modifiers, healing products or anti-free radicals.
2. The safety of a colorant dispersion
All of the components could be hazardous to human health.
2.1 The pigments
The pigment size is not often taken into consideration, however:
- An overly large granulometry (diameter of the pigment particles) can cause chronic intolerance (foreign body granuloma). Low-end mineral pigments pose this hazard.
- Overly small granulometry (nanoparticles), in addition to its poor performance in skin, may pose a hazard to the organism and is highly debatable (mandatory declaration 6 months before a cosmetic product is placed on the market, for example). Organic pigments pose this hazard.
- To prevent the disappearance of organic pigments, some manufacturers use tinted PMMA (polymethyl methacrylate). This is prohibited.
- Other coatings and complexations are harmless (mica, fluorphlogopite and quartz) as long as they do not exceed the maximum impurity level (especially tin) and their granulometry is not too high.
2.1.3 Mineral origin
- Some mineral pigments are prohibited: cinnabar (mercury sulphide), a potential carcinogen and photosensitizer, cadmium green and yellow, which are photosensitizing, etc.
- Some pigments must be free of toxic ions: chromates for chromium oxides, cyanide for Prussian blue.
- Finally, all mineral pigments may contain impurities that could have a toxic effect. Luckily, there is a maximum level set by the law which guarantees product safety: table 3 of ResAP(2008)1. In comparison, the levels permitted for food colourings are much higher (and we consume them every day) than the maximum levels permitted for pigmentation. Thus, dietary iron oxide can contain up to 20 ppm (parts per million or mg/kg) of lead, while there must be less than 2 ppm for tattooing. Dietary cadmium can have levels up to 5 ppm, and must be less than 0.2 ppm for micropigmentation, etc. The only legal ambiguity concerns the maximum admissible level of nickel. Both French and European law requires “a level as low as technically possible”. Requests for clarification made to the ANSM and the DGCCRF have received such varying responses as “It is like the permitted arsenic level” (they do not have the same toxicity) and “no level has been set, you are responsible for demonstrating the safety of the nickel level in your products”. As a conservative estimate, health organizations believe that a level of 0.5 ppm (using the extractive method) is sufficiently low to have no health consequences. The nickel level permitted for dietary iron oxides is 200 ppm, or 400 times more than the level acceptable for tattooing! In any case, while nickel can be allergenic, it is not carcinogenic at such low doses and with one-time application, and there is a lot more nickel in the steel of the needles than in the pigments: nearly all stainless steels, including surgical steel, are made of an iron and nickel alloy.
- Mineral pigments are not sources of aromatic amines (strictly prohibited), nor of PAHs or benzo(a)pyrene, with very low authorized levels.
- Natural mineral colorants are authorized in Organic products
2.1.4 Organic origin
- Some organics are prohibited: Table 2 of ResAP(2008)1.
- The authorized organics must not contain carcinogenic aromatic amines: Table 1 of ResAP(2008)1. Aromatic amines are a known cause of occupational illnesses and urinary tract cancer. Azoic pigments (50% of organic pigments) may contain aromatic amines or release them under a laser beam, as they are formed by association with aromatic amines. But these are not the only organic pigments that might contain aromatic amines (a test report is required to disprove this). The simplest aromatic nucleus is benzene, which can attach to an amino radical (-NH2) to form a colorant, aniline. The aromatic derivatives are specifically released by the by-products of burning diesel.
- Other organic pigments may exceed the very low authorized levels of PAH (polycyclic aromatic hydrocarbon) or benzo(a)pyrene. This is the case for carbon, which is obtained through the incomplete combustion of organic components.
- Organics can contain heavy metals, but less frequently than minerals.
- All organic pigments (except natural carminic acid from the cochineal) are prohibited in Bio products.
2.2 The dispersant
- Most of the usual products are harmless: water, propylene glycol (mainly its Bio equivalent); or have positive properties (glycerine is a moisturizer).
- Other ingredients must be avoided or used with precaution, such as polymers.
- Nearly all fixing agents are prohibited.
- Some are useful: pH modifiers, antiseptics (alcohols, though they can be irritating), vitamins, antioxidants…
- Others, such as preservatives, are prohibited – all of them, not just parabens, phenoxyethanol and isothiazolinone.
2.4 The contenair
- Depending on the vial’s quality (PVC, for example) and the composition of the tattooing product, there may be an interaction causing the breakdown of the plastic or of the product’s organic compounds, leading to toxicity.
- A container-content test must be performed by the manufacturer.
2.5 The sterilization method
- Insufficient or poorly controlled irradiation can be dangerous by failing to sterilize the product or shortening the duration of sterility (after opening or when the product is stored for a long time).
- Normal or excessive sterilization may alter the plastic vial, the pump or the product and create toxic metabolites due to breakdown.
- Sterilizing a product contaminated during manufacturing may produce bacterial endotoxins (pyrogens). Manufacture in a clean room (with a controlled atmosphere) is strongly recommended.
2.6 Storage conditions
Poor storage conditions (temperature, humidity, microbial environment) or poor disinfection of the pump after use can also affect the product’s quality or the preservation of sterility.
The very strict laws on tattooing products on both the European (ResAP(2008)1) and French levels (Order of 06 March 2013) guarantee safety for consumers using products produced by a manufacturer who complies with the law and cares about consumers’ health. There is no risk involved with using either organic or mineral pigments, as long as they comply with the law (an analysis report for the raw materials or the finished product should be enough to reassure the user). It is even recommended to use both types of pigments in order to benefit from each type’s unique properties and their synergy and to cancel out their non-qualitative effects.
It is the professional’s responsibility to ensure the product’s compliance (labelling, analysis reports) and to use the product according to the manufacturer’s instructions: storage conditions, use-by date, period after opening.
With everybody’s involvement, we can ensure your clients’ safety.
Dr JP TIZIANO
Research and Development DirectorLaboratoires BIOTIC Phocea
A French designer and manufacturer of medical devices