Are Pigment safe?
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To meet product safety, environmental protection, and health requirements, materials and products using pigments must comply with regulatory requirements in countries and regions around the world. The most important and concerning of these are requirements for chemical substance control, particularly the chemical requirements for colorants, which are important additives in product materials. These requirements cover a wide range of consumer products, including toys, textile materials and accessories (such as zippers and buttons), cosmetics (such as nail polish and lipstick), electronic and electrical products, food containers and food contact materials or products, and automotive materials.
- Acute Toxicity of Chemicals
The most commonly used metric for measuring acute toxicity is the LD50 (lethal dose). LD50 stands for the median lethal dose. A simple definition is the dose required to cause death in 50% of a group of test animals, such as rats. The LD50 is expressed in mg/kg body weight. Lower LD50 values indicate a more potent poison; higher LD50 values indicate a less toxic poison. The European Union defines three acute toxicity categories (rat oral) for substances.
LD50 ≤ 25 mg/kg; extremely toxic
LD50 = 25-200 mg/kg; toxic
LD50 = 200-2000 mg/kg; harmful
Regarding the acute toxicity of colorants, a monograph reviewed 194 pigments and found that the majority had oral LD50 values greater than 5000 mg/kg, with no reported values below 2000 mg/kg. Considering that the oral LD50 value of table salt (NaCl) is 3000 mg/kg, this would be equivalent to an average-weight person ingesting 350g of pigment, which is unlikely. Therefore, the conclusion is that colorants generally have low acute toxicity. Pigments are typically excreted through the gastrointestinal tract, not through the urine.
- Impurities in Organic Pigments
Organic pigments are widely used as colorants in plastic consumer products, cosmetics, toys, and food packaging. Therefore, in addition to the toxicological and ecological properties of the pure pigments, the potential for trace impurities generated during production must be considered, potentially impacting their use in these consumer products. Possible impurities are listed below.
(1) Certain heavy metal compounds Some organic pigments (C.I. Pigment Red 48:1) use heavy metal salts (barium) as pigments and are therefore not recommended for use in food packaging materials and toys.
(2) Aromatic amines Aromatic amines are only allowed to appear in very low amounts as components of pigment synthesis in organic pigments. For use in food contact packaging materials, the upper limit has been clearly defined: Aromatic primary amines: <500ppm (mg/kg, total amount); 4-aminobiphenyl, benzidine, 2-naphthylamine, 2-methyl-4-chloroaniline: <10ppm (mg/kg, total amount).
(3) Polychlorinated biphenyls Polychlorinated biphenyls (PCBs) are mainly harmful because their persistent residues in the environment are more harmful than to humans. In the EU, chemicals containing 50ppm or more of polychlorinated biphenyls (PCBs) or PCTs are classified as polychlorinated biphenyls.
(4) Dioxins Pigment Violet 23 is prepared by condensing tetrachlorobenzoquinone with N-ethylcarbazole. During the synthesis process, a small amount of dioxins is inevitably formed.
- Safety of Bischlorobiphenyl Pigments
Yellow-orange organic pigments synthesized from 3,3-bischlorobenzidine (DCB) are important azo pigments. DCB pigments are a key component of plastic coloring due to their vibrant color, high tinting strength, and affordability. Examples include Pigment Yellow 13, 14, 17, 81, and 83, and Pigment Orange 13 and 34.
Concerns persist about whether DCB series pigments used in chemical fiber non-woven textile materials, clothing zippers and button accessories, and food packaging materials meet the safety requirements of domestic and international ecological and environmental regulations.
Bischlorobenzidine is a probable carcinogen. The International Agency for Research on Cancer (IARC) classifies compounds into three categories based on their carcinogenicity: 1 – Carcinogenic to humans; 2A – Probably carcinogenic to humans; and 2B – Possibly carcinogenic to humans.
Bischlorobenzidine is a Category 2B carcinogen, and its carcinogenicity primarily occurs through the formation of adducts with nucleotides (DNA), leading to DNA mutagenesis. Polychlorinated biphenyls (PCBs) are highly bioaccumulative and difficult to biodegrade, significantly damaging the human endocrine system. Consequently, strict international regulations exist. The European Union prohibits the use of products containing PCBs exceeding 10 mg/kg; the United States prohibits the production, processing, sale, and use of products containing PCBs exceeding 25 mg/kg. The International Association for Research and Testing of Textile Ecology (Oske-Tex Standard 100 Special Technical Conditions for General Machines) stipulates that the content of 24 aromatic amines shall not exceed 20 mg/kg, and DCB is listed among them, see Table 1.
Table 1. Oeko-Tex Standard 100 lists 24 aromatic amines
| Serial number | name | CAS Number | Serial number | name | CAS Number |
| 1 | 4-Aminoaniline | 92-67-1 | 13 | 3,3-Dimethyl-4,4-diaminodiphenylmethane | 838-88-0 |
| 2 | Benzidine | 92-87-5 | 14 | 2-Methoxy-5-methylaniline | 120-71-8 |
| 3 | 2-Methyl-4-benzidine | 95-69-2 | 15 | 4,4-Methylenebis(o-chloroaniline) | 101-14-4 |
| 4 | 2-Naphthylamine | 91-59-8 | 16 | 4,4-Diaminodiphenyl ether | 101-80-4 |
| 5 | o-Aminoazotoluene | 97-56-3 | 17 | 4,4-Diaminodiphenyl sulfide | 139-65-1 |
| 6 | 2-Amino-4-nitrotoluidine | 99-55-8 | 18 | o-Benzylamine | 95-53-4 |
| 7 | p-Chloroaniline | 106-47-8 | 19 | 2,4-Diaminotoluene | 95-80-7 |
| 8 | 2,4-Diaminoanisole | 615-05-4 | 20 | 2,4,5-Trimethylaniline | 137-17-7 |
| 9 | 4,4-Diaminodiphenylmethane | 101-77-9 | 21 | o-Anisidine | 90-04-0 |
| 10 | 3,3-Dichloroaniline | 91-94-1 | 22 | 2,4-Dimethylaniline | 95-68-1 |
| 11 | 3,3-Dimethoxybenzidine | 119-90-4 | 23 | 2,6-Dimethylaniline | 87-62-7 |
| 12 | 3,3-Dimethylbenzidine | 119-93-7 | 24 | p-Aminoazobenzene | 1960-9-3 |
Note:
Category 1: Aromatic amines that are carcinogenic to humans (4 types, 1 to 4);
Category 2: Aromatic amines that are carcinogenic to animals and may be carcinogenic to humans (20 types, 5 to 24).
- Heavy Metals in Inorganic Pigments
With the exception of titanium dioxide, carbon black, and ultramarine, all inorganic pigments contain heavy metals. Like other substances, heavy metals are considered hazardous to humans and the environment when present above certain concentrations. The presence of other heavy metals depends on the type and form of the heavy metal.
4.1 Chromium Heavy Metal
Chromium oxides contain either trivalent or hexavalent chromium, and their effects vary significantly. Hexavalent chromium compounds (chromates) have a strong tendency to transform into trivalent chromium compounds, releasing oxygen, resulting in strong oxidizing and toxic effects on organisms. They are up to 1,000 times more toxic to humans, animals, and plants than trivalent chromium compounds.
- Lead chromate pigments: Lead chromate pigments contain lead and hexavalent chromium, both of which have chronic hazards. Lead chromate is a low-solubility lead compound. Dissolved lead is found in hydrochloric acid and gastric acid at concentrations that lead to lead accumulation in the body. Ingestion of high levels of lead can disrupt hemoglobin synthesis. As a precautionary measure, the European Union has classified lead chromate as a Category 3 carcinogen (suspected carcinogenic potential).
- Chromium Oxide Pigment Green Chromium oxide pigment green contains only trivalent chromium. Under natural conditions, no free chromium particles are released from the chromium oxide pigment green. Even under strong acid conditions (pH = 1-2), only a small amount (mg/kg) of chromium (III) is released. Chromium (III) oxide can only be oxidized to chromium (VI) when heated, especially under alkaline conditions.
4.2 Cadmium Heavy Metal
Cadmium pigments are compounds with low solubility, but are soluble in dilute acid (at concentrations equivalent to gastric acid). Long-term oral ingestion of cadmium pigments can cause accumulation in the body. The European Commission has classified cadmium sulfide as a Class III carcinogen, but cadmium pigments are not included.
CHROMÉCLAIR offers Base coats, Top coats, solid color gel polish without HEMA, and hema free cat eye gel polish.
Their website also features nail art tutorials, such as:
How to Do the Amber Gold Foil Nail Art at Home?
How to do retro 3D floral nail art at home?