2-(1,3-dihydro-3-oxo-2H-indol-2-ylidene)-1,2-dihydro-3H-indol-3-one

Toxicological Summary

Workers - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Workers - Hazard via dermal route

Systemic effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

Workers - Hazard for the eyes

Local effects

Hazard assessment conclusion:

no hazard identified

Additional information - workers

As up to 1% aniline can be contained in the Indigo registered, the substance has to be classified for this possible aniline content despite the fact that no adverse effects were noted up to the highest dose levels tested with Indigo containing up to 3% aniline and methylaniline as a sum, or Indigo with aniline and methylaniline each below 1%. Due to the fact that no adverse effects were noted in all studies conducted with Indigo complying to the sameness criteria as agreed on in the SIEF, no DNELs can be derived from these studies and consequentially, any possible risk arising from the test substance has to be assessed qualitatively.

In the production of Indigo aniline is recognized as a substance with an occupational exposure level that has to be monitored. The Senatskommission der Deutschen Forschungsgemeinschaft (DFG) zur Prüfung gesundheitsschädlicher Arbeitsstoffe defined the maximum workplace concentration (MAK) to be 7.7 mg/m³ (MAK- und BAT-Werte-Liste 2014).Technical measures as well as personal protective equipment are in place to ensure that the workers' exposure to aniline is efficiently controlled. Monitoring on exposure levels is in place and demonstrates that MAK-values are by far not exceeded. Respective data is available at the DyStar production site. According to current knowledge, a health risk due to exposure to aniline therefore can be excluded.

Indigo dyeing is a combination of a continuous and exhaustion dyeing process and the remaining dyeing bath after the dyeing process is not released into the environment but stored to be used in the next dyeing campaign. The standard dyeing machines have 3 to 12 dye-boxes containing between 200 to 1500 L dye-bath each. Dyeing is done at room temperature using dyeing liquors containing max. 0.6% Indigo in its reduced soluble form (Leuco Indigo). During the dyeing process, Indigo is constantly kept at the pre-defined concentration of max. 0.6% in these dye-boxes. Indigo is only soluble in its reduced form at a strong alkaline pH. To avoid contact of the dye-bath with oxygen and hence oxidise the Leuco Indigo to the insoluble Indigo form, these dye-boxes are usually kept in a closed system with an inert gas (e.g. nitrogen) atmosphere. Assuming a concentration of 1% aniline in the used Indigo batch, this would lead to an aniline concentration of max. 0.006% in the dye-bath. Due to the low application temperature and its low vapour pressure at room temperature (0.4 hPa, 20°C; 1.33 hPa at 35°C) aniline is mainly solubilized and does not vaporize (< 1%) into the ambient atmosphere [Lyons et al. Mechanisms and pathways of aniline elimination from aquatic environments, Appl Environ Microbiol. 48(3): 491–496, 1984]. In industrial settings usually there are general ventilation system installed with exhaust fans directly above the dyeing machine. By these, the air is drawn away from the workers' breathing zone. Such installations have proven to be effective and sufficient to exclude a health risk due to worker exposure to aniline. Maximum workplace concentration of 7.7 mg/m³ are by far not exceeded. Furthermore, all workers have to wear suitable personal protection, such as overalls/lab coats, gloves and goggles, as dyeing is done in an alkaline environment.

During the dyeing process, a distinct amount of aniline attaches to the yarn surface and is washed-off during the washing process. After this step, the yarn is automatically conveyed to an airing passage where the Leuco Indigo is transformed to its insoluble pigment form, which is blue. The vast majority of the aniline remains in the wash water after washing the dyed yarn and remains in the effluent after recycling the Indigo and is rapidly biodegraded in the wastewater treatment plant to CO₂ [Lyons et al. 1984].

General Population - Hazard via inhalation route

Systemic effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

General Population - Hazard via dermal route

Systemic effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

Local effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

General Population - Hazard via oral route

Systemic effects

Long term exposure

Hazard assessment conclusion:

no hazard identified

Acute/short term exposure

Hazard assessment conclusion:

no hazard identified

DNEL related information

General Population - Hazard for the eyes

Local effects

Hazard assessment conclusion:

no hazard identified

Additional information - General Population

Indigo as defined by the sameness criteria did not show any adverse systemic or local effects either during short-term or long-term exposure. Hence, there is no hazard for the consumer during use of the respective articles.