The facts on o-Toluidine

Estimates of current numbers of workers exposed to ortho-toluidine (o-toluidine) in the EU are not available. In 2011, based on data from 2006/2007, 5.500 workers were estimated to be exposed, of which 3.100 were in manufacture of chemicals, chemical products and man-made fibres or manufacture of rubber products.

Exposure occurs mainly by inhalation and dermal absorption; no direct skin contact is necessary. Uptake by ingestion and eye contact may also occur.

o-Toluidine is classified as a harmonized entry under the CLP Regulation in Carcinogenicity Category 1B (presumed carcinogenic potential for humans based largely on evidence in experimental animals). In humans, o-toluidine may cause urinary bladder cancer. Penetration through the skin may contribute to the overall body burden.

Where risks occur

Exposures to o-toluidine have been much higher historically but can still occur today in several occupational settings, particularly in the chemical industry during the manufacture, processing, sampling, or transfer of o-toluidine or in its use as an intermediate, especially in dye production, and in the manufacture of plant protection products. Other exposure situations might occur due to the release from azo dyes or colorants used in textiles, printing inks, plastics, lubricants, and mineral oil products; release from additives during thermal processes such as vulcanization; thermal decomposition of organic binders, especially in casting processes; handling or heating of coal-tar containing materials; laboratory and research activities.

More about the substance

o-Toluidine is produced industrially by nitration of toluene to give a mixture of nitrotoluenes; it is the most important of the three isomeric toluidines. It is a colourless liquid although commercial samples are often yellowish. o-Toluidine is an intermediate in the biodegradation of o-nitrotoluene and thus detected at former munition sites. o-Toluidine is formed during pyrolysis.
No direct consumer use is known for o-toluidine since it is banned from cosmetics by the EU Cosmetics Regulation. The use of azo dyes that release o-toluidine during degradation is not permitted for textiles and other consumer articles in the EU. Thus, an exposure of consumers and of the environment due to releases from consumer products appears to be negligible.

For o-toluidine, an EU-wide binding occupational exposure limit value of 0.5 mg/m³ in the air is in place.

Health risks that may occur

o-Toluidine is well absorbed after inhalation and via the skin. Oral exposure is not relevant at the workplace.
There are no reports on effects following acute exposure, but based on experimental animal data, an acute irritant effect on eyes and skin is assumed.

Urinary bladder cancer is considered the relevant health effect in humans. In some member states, this is a recognised occupational disease associated with former exposure to o-toluidine.

The latency period between exposure and appearance of o-toluidine-related bladder cancer varies strongly but is typically considered to be within 15 to 40 years.

What you can do

Substitution should be considered in applications where feasible. To avoid adverse health effects, it is of utmost importance to reduce exposure below the binding occupational exposure or health-based limit value. In industrial processes, examples of technical control measures are enclosed systems, general exhaust and local exhaust ventilation. Even when working with closed systems, exposure can occur, e. g. during sampling tasks or maintenance. Measurements and control measures are of relevance there. Other recommended work practices include providing employees with hazard information and training, and general working hygiene standards for chemical handling areas. Workers in maintenance and cleaning should be trained as well. It is recommended to involve an occupational physician. Be aware that the exposure assessment should be supported with biomonitoring, if applicable under national legislation, because o-toluidine is well absorbed via the skin. Workers need to be aware of the effects of exposure. Personal protective equipment should only be used as a last resort, after introducing the possible engineering solutions.

References: ECHA, IOM, SCOEL