Pigments & Toxicology

01 Overview of Pigment-Related Legislation

To meet product safety and environmental requirements, plastics and plastic products must comply with regulations across countries and regions, particularly concerning chemical substance controls. Among these, chemical specifications for colorants (pigments) receive significant attention. Depending on the region and product type, relevant requirements may target the pigments themselves, the plastic materials, or encompass general provisions.

The effects of chemicals on mucous membranes such as skin and eyes are assessed through animal contact tests in laboratories and classified based on irritation or corrosion severity. Research indicates that the vast majority of organic pigments are non-irritating to skin and mucous membranes; among 192 commonly used organic pigments, only 6 exhibited mild irritation in experimental animals.

Organic pigments show no toxicity in repeated exposure tests and are excluded from substances requiring the R48 label (repeated exposure causes serious harm) under EU regulations.

Inorganic pigments often contain heavy metals (defined as having a density >4.5 g/mL). Except for aluminum powder, carbon black, and ultramarine blue/violet, most contain heavy metals. Testing indicates that, apart from chromium and cadmium-based pigments, most inorganic pigments are harmless in terms of toxicology and ecology.

02 Toxicology and Ecology of Pigments

Pigments are poorly soluble in water and common solvents. Their ecological impact primarily stems from emissions of exhaust gases and wastewater during production.

·Waste Gas: Organic pigment dust pollution requires airborne concentrations below 6 mg/m³ and must undergo purification before discharge. Production personnel must wear protective equipment.

· Wastewater: Production effluent may contain carcinogens such as aromatic amines and nitrites, necessitating physical and biological treatment to render it non-toxic to fish.

Extensive investigations confirm that the toxicology and ecology of dyes encompass nine aspects:

2.1 Acute Toxicity

Refers to toxicity resulting from a single exposure. Tests on mice with 108 organic pigments showed their LD₅₀ values all exceeded 5000 mg/kg, higher than table salt (approximately 3000 mg/kg). The EU defines substances with an LD₅₀ below 2000 mg/kg as toxic. ETAD testing of over 4,400 dyes and pigments revealed that only about 8% exhibit acute toxicity, primarily cationic dyes, metal complex dyes, and products containing auxiliaries. Currently, 13 acutely toxic pigments are banned (Table 1), including 6 basic pigments, 2 acid pigments, 1 direct pigment, 3 ice-dye bases, and 1 phthalocyanine.

Table 1: Currently Banned Acute Toxicity Pigments on the Market

Serial Number	Pigment	Serial Number	Pigment
1	Basic Yellow 21	8	Acid Orange 165
2	Basic Red 12	9	Direct Orange 62
3	Basic Violet 16	10	Ice Dye Base 20
4	Basic Blue 3	11	Ice Dye Base 24
5	Basic Blue 7	12	Ice Dye Base 41
6	Basic Blue 81	13	Ingrain Blue 2:2
7	Acid Orange 156

These acutely toxic pigments exhibit the following characteristics: water-soluble pigments constitute the vast majority; they readily dissolve in polar solvents such as ethanol; and their molecular structures contain strong electron-donating substituents like amino groups or substituted amino groups.

2.2 Repeated Exposure Toxicity

In repeated exposure tests using sublethal doses on animals, most dyes and pigments showed no organ toxicity at doses not exceeding 1000 mg/kg.

2.3 Irritation

Refers to irritation effects on skin and mucous membranes. ETAD testing of 68 dyes and pigments found approximately 30% to cause eye or skin irritation, partly attributable to additives.

2.4 Allergenicity

Certain pigments may cause skin or respiratory allergies. Allergenic pigments in textiles must be controlled below 0.006%. ETAD identified 27 allergenic pigments (Table 2), including 26 disperse dyes and 1 acid dye; the Oeko-Tex Standard 100 lists 20. Their common characteristics include: predominantly azo or anthraquinone structures, relatively low molecular weight (230 – 400), presence of strong electron-donating groups such as hydroxyl or amino, and solubility in organic solvents.

Table 2 Currently Known Allergenic Pigments

Serial Number	Pigment	Serial Number	Pigment
1	C.I. Disperse Yellow 1	15	C.I. Disperse Blue 1
2	C.I. Disperse Yellow 3	16	C.I. Disperse Blue 3
3	C.I. Disperse Yellow 9	17	C.I. Disperse Blue 7
4	C.I. Disperse Yellow 39	18	C.I. Disperse Blue 26
5	C.I. Disperse Yellow 49	19	C.I. Disperse Blue 35
6	C.I. Disperse Orange 1	20	C.I. Disperse Blue 85
7	C.I. Disperse Orange 3	21	C.I. Disperse Blue 102
8	C.I. Disperse Orange 13	22	C.I. Disperse Blue 106
9	C.I. Disperse Orange 37	23	C.I. Disperse Blue 124
10	C.I. Disperse Orange 76	24	C.I. Disperse Brown 1
11	C.I. Disperse Red 1	25	C.I. Disperse Black 1
12	C.I. Disperse Red 11	26	C.I. Disperse Black 2
13	C.I. Disperse Red 15	27	C.I. Acid Black 48
14	C.I. Disperse Red 17

2.5 Mutagenicity

Genotoxicity is assessed through tests such as the Ames assay. Over two-thirds of more than 200 dyes exhibit no mutagenicity, while only one of 36 organic pigments demonstrates genotoxicity. Impurities may also contribute to mutagenic effects.

Table 3 lists the mutagenicity of 25 organic pigments tested using the Ames method, revealing only minor mutagenic effects in a few specific organic pigment varieties.

Table 3: Mutagenicity Test Results of Organic Pigments Using the Ames Assay

Pigments	Dye Index Structure Number	Results	Pigments	Dye Index Structure Number	Results
C.I.Pigment Yellow 1	11680	Negative	C.I. Pigment Red 49:2	15630:2	Negative
C.I.Pigment Yellow 12	21090	Negative	C.I. Pigment Red 53:1	15585 1	Negative
C.I.Pigment Yellow 74	11741	Negative	C.I. Pigment Red 57:1	15850 1	Negative
C.I.Pigment Orange 5	12075	Weak positive	C.I. Pigment Red 63:1	158801	Negative
C.I.Pigment Orange 13	21110	Negative	C.1. Pigment Blue 15	74160	Negative
C.I.Pigment Red 1	12070	Weak positive	C1. Pigment Blue 15:1	74160.1	Negative
C.I.Pigment Red 4	12085	Negative	C1. Pigment Blue 1512	74160 2	Negative
C.I.Pigment Red 22	12815	Negative	C1. Pigment Blue 15:3	74160-3	Negative
C.I.Pigment Red 23	12355	Negative	C1. Pigment Blue 15:4	74160 4	Negative
C.I.Pigment Red 48:1	15865-1	Negative	C.1. Pigment Green 7	74260	Negative
C.I.Pigment Red 48:2	15865 2	Negative	C.1. Pigment Green 36	74265	Negative
C.I.Pigment Red 49	15630	Negative	C.1. Pigment Violet 19	73900	Negative
C.I.Pigment Red 49:1	15630:1	Negative

2.6 Chronic Toxicity and Carcinogenicity

Certain dyes may decompose to release carcinogenic aromatic amines or exhibit direct carcinogenicity. ETAD identified 143 dyes potentially decomposing into carcinogenic amines, with 11 classified as direct carcinogens—most featuring azo structures or amino substituents. Pigments like copper phthalocyanine may adsorb to serum proteins and accumulate, affecting blood composition.

2.7 Aquatic Toxicity and Biodegradability

ETAD testing indicates that 59% of dyes and pigments exhibit low fish toxicity (LD50 > 100 mg/L), while only 2% demonstrate high toxicity (LD50 < 1 mg/L). In bacterial toxicity tests, a small number of dyes inhibit bacterial growth.

2.8 Irritation to Skin and Mucous Membranes

Among 192 organic pigments, only a very small number exhibit irritation to the skin and mucous membranes of experimental animals, including the effects of additives.

2.9 Impurities in Pigments

· Trace aromatic amines: Countries impose limits on their content; for example, food packaging materials require levels below 50μg/g.

· Trace Heavy Metals: U.S. DCMA research indicates organic pigment heavy metal levels comply with regulations.

· Polychlorinated Biphenyls (PCBs): Strictly restricted in Europe and the U.S., may be present in certain azo pigments or pigments produced using chlorinated solvents.

In summary, organic pigments exhibit no acute toxicity, repeated-dose toxicity, significant mutagenicity, or carcinogenicity under conventional conditions. Germany’s 1994 ban applies only to dyes, not organic pigments. However, attention must still be paid to harmful aromatic amines in production auxiliaries, additives, and raw materials. Additionally, monitor varieties prone to decomposing harmful substances at high temperatures (e.g., bichlorobenzidine-based pigments) and byproducts like dioxins that may form during wastewater treatment.