Solvent Orange 2 is a synthetic azo dye primarily used in industrial applications such as coloring plastics, waxes, oils, and some inks. It is classified as a Category 2 carcinogen by the European Union and as a Group 2B carcinogen by the International Agency for Research on Cancer (IARC), meaning it is "possibly carcinogenic to humans." A significant concern regarding Solvent Orange 2 is its ability to release hazardous aromatic amines, such as o-Toluidine, through the cleavage of the azo bond. These aromatic amines are classified as EU22 hazardous substances and are recognized carcinogens. Solvent Orange 2 is also included in the Screening Assessment for Aromatic Azo and Benzidine-based Substance Grouping Certain Azo Solvent Dyes, as noted in Section 7.2.2 of Environment Canada’s assessment.
Chemical Composition and Structure
Solvent Orange 2 is an azo dye composed of an azo bond (-N=N-) connecting two aromatic rings. Its chemical structure includes functional groups that can degrade into aromatic amines, specifically o-Toluidine, a known carcinogen. The presence of the azo bond gives the dye its bright orange color, but also poses a significant safety risk due to the potential degradation of the compound into dangerous by-products.
Physical Properties
Solvent Orange 2 appears as a bright orange crystalline powder. It is soluble in organic solvents such as oils and waxes but insoluble in water. It has good light and heat stability, making it suitable for various industrial applications where resistance to harsh environmental conditions is required.
Production Process
It is produced via an azo coupling reaction, where aromatic amines are treated with nitrous acid to form a diazonium salt, which is then coupled with another aromatic compound to form the azo bond. During production, strict control is necessary to prevent the release of hazardous aromatic amines, such as o-Toluidine, which pose a significant health risk.
Applications
Plastics and Waxes Coloring: Solvent Orange 2 is used to color synthetic materials such as plastics and waxes due to its high solubility in organic solvents and stability to light.
Industrial Inks: The dye is also used in industrial inks and coatings where a vivid and durable color is needed.
Oils and Lubricants: Solvent Orange 2 is used in some applications to color solvent-based oils and lubricants.
Health and Safety Concerns
Carcinogenicity
Solvent Orange 2 is classified as a Category 2 carcinogen by the European Union and as a Group 2B carcinogen by IARC, meaning it is "possibly carcinogenic to humans." The primary concern is its ability to degrade into hazardous aromatic amines such as o-Toluidine, through the cleavage of the azo bond. o-Toluidine is a well-known carcinogen, particularly associated with bladder cancer. This makes Solvent Orange 2 a highly controlled substance in industrial settings and banned in many consumer products.
Toxicity
In addition to its carcinogenic potential, Solvent Orange 2 can cause acute toxicity if ingested, inhaled, or absorbed through the skin. Prolonged exposure may lead to skin and respiratory irritation, as well as an increased risk of cancer. For this reason, strict safety measures are necessary in industrial processes involving this dye, with protocols aimed at minimizing worker exposure.
Environmental and Safety Considerations
Solvent Orange 2 is not biodegradable and can accumulate in the environment, particularly in aquatic ecosystems. Its ability to degrade into toxic aromatic amines presents a significant environmental health risk. Regulatory frameworks enforce strict waste management and disposal protocols to prevent environmental contamination. Companies using this dye must adhere to stringent regulations to protect the environment and public health.
Regulatory Status
Due to its classification as a possible carcinogen, the use of Solvent Orange 2 is heavily regulated in the European Union and many other countries. It is banned in cosmetics, food products, and textiles intended for consumers. However, it continues to be used in certain industrial applications where strict safety measures are enforced.
Applications Under Strict Control
Manufacturing: Despite the carcinogenic risk, Solvent Orange 2 is still used in some industrial applications for coloring plastics and waxes.
Research and Analytical Use: In some research contexts, it is used under controlled conditions where strict safety protocols are applied.
Safety
The problem with azo dyes (monoazo or diazo) is photocatalytic degradation leading to oxidation and the subsequent formation of impurities such as aromatic amines, some of which have carcinogenic activity. (Chung KT, Stevens SE Jr, Cerniglia CE. The reduction of azo dyes by the intestinal microflora. Crit Rev Microbiol. 1992;18(3):175-90. doi: 10.3109/10408419209114557. )
Overall, the study cited in Bibliography finds that available health effects data for this substance are limited. Oil Orange SS induced chromosomal damages in vivo and gene mutations in bacteria with metabolic activation and intestinal tumours in mice via oral administration, indicating carcinogenicity and genotoxicity are the main health concerns for Oil Orange SS.
Molecular Formula C17H14N2O
Molecular Weight 262.30 g/mol
CAS 2646-17-5
UNII E939MCU4ID
EC Number 220-162-8
CHEMBL1976978
CHEBI:82364
DTXSID6025808
Synonyms:
Solvent Orange 2
Orange OT
Oil Orange SS
Fat Orange RR
Bibliografia__________________________________________________________________________
Screening Assessment Aromatic Azo and Benzidine-based Substance GroupingCertain Azo Solvent Dyes. Environment and Climate Change Canada Health Canada May 2016
Synopsis. Pursuant to sections 68 or 74 of the Canadian Environmental Protection Act, 1999 (CEPA 1999), the Ministers of the Environment and of Health have conducted a screening assessment on 22 Azo Solvent Dyes. These substances constitute a subgroup of the Aromatic Azo and Benzidine-based Substance Grouping being assessed as part of the Groupings Initiative of Canada’s Chemicals Management Plan (CMP) based on structural similarity and applications. Substances in this grouping were identified as priorities for assessment as they met the categorization criteria under subsection 73(1) of CEPA 1999 and/or were considered as a priority based on other human health concerns. The Chemical Abstracts Service Registry Number (CAS RN)1, Domestic Substances List (DSL) name, and Colour Index (C.I) name or common name of the 22 substances are presented in the following table.....
Solvent Orange 2 
