Occupational airborne allergic contact dermatitis from 2-aminothiophenol

ARTICLE

2-Aminothiophenol (also known as 2-aminobenzenethiol or p-mercaptoaniline) (CAS 137-07-5) is an aromatic hydrocarbon used as a chemical intermediate for chemical and biomedical research, and for the synthesis of various drugs.

We report a case of occupational contact dermatitis in a chemical technician, who works in a plant which produces intermediate pharmaceutical substances.

Case report and methods

A 36-year-old non atopic man, employed as a technician for the last 12 years in a plant producing intermediate pharmaceutical products, developed recurrent episodes of eczema of the face, with improvement of the symptoms when away from work.

The onset of the dermatitis had developed 15 days after accidental exposure to vapors of 2-aminothiophenol coming from the heating chambers, which had been opened by the technician when he was wearing no personal protective devices except gloves. The clinical manifestations featured a severe eczematous dermatitis with diffuse, symmetrical involvement of the face, including the eyelids, sub-mental region and retroauricular folds.

Recurrences of the dermatitis occurred after inspection visits in the plant department and when drainage procedures of containers with residual 2-aminothiophenol were carried out.

Patch tests were performed with the SIDAPA (Italian Society of Allergological Occupational and Environmental Dermatology) standard series and samples of chemicals to which the patient could have been exposed in the working environment. Readings were made on D2 and D4 and yielded a positive reaction only to 2-aminothiophenol 0.1% and 0.01% eth. Ten controls tested with aminothiophenol 0.1% eth. gave negative results.

The patient was moved to a different job position in the plant, leading to complete recovery of the dermatitis.

Discussion

Our case report describes a chemical technician working for a pharmaceutical company in the production of intermediate substances such as hydroxythiazepinone; the latter is synthesized using 2-aminothiophenol as a reaction intermediate. The patient showed the classic picture of occupational airborne allergic contact dermatitis [1] following accidental exposure to 2-aminothiophenol vapors when wearing no protective devices.

In the literature, 2 cases of allergic reaction to 2-aminothiophenol have been observed. The first case featured a systemic contact dermatitis that appeared in a chemistry student after inhalation of the vapors of 2-aminothiophenol. The student had become sensitized to this substance after it spilled on his pants during a chemical reaction [2]. In the second case, recurrent airborne contact dermatitis arose in a development technician who used 2-aminothiophenol for a chemical process [3].

In our case the onset of airborne contact dermatitis was facilitated by the particular circumstances of the exposure to the chemical agent.

2-Aminothiophenol is usually in a condensed state at room temperature; to make it fluid it is placed in melting chambers at a temperature of nearly 30° C. The opening of the melting chambers originated a brief exposure to high levels of the vapors. This observation suggests that sensitization may be initiated by exposure to high concentrations of 2-aminothiophenol during spills. The recurrences were most likely related to the small amounts of vapor occasionally present at the worksite.

This study demonstrates the importance of performing patch testing with substances used at work when investigating subjects with work related dermatitis, especially airborne dermatitis. In order to identify the causal agent, detailed information on the different substances used in the industrial processing procedures is essential, together with the related risk, source of occupational exposure and any occurrence of episodes of intense exposure.

Article accepted on 23/7/02

REFERENCES

1. Lachapelle JM. Occupational airborne skin diseases. In: Kanerva L, Elsner P, Wahlberg JE, Maibach HI, eds. Handbook of occupational dermatology. Springer-Verlag, Berlin, Heidelberg, New York 2000; 193-9.

2. Ducatman AM, Rigby M. Systemic contact dermatitis after inhalation of 2-aminothiophenol. Contact Dermatitis 1988; 18: 57-8.

3. Sommer S, Wilkinson SM, Quinlan R. Exposure-pattern dermatitis due to 2-aminothiophenol and 2-aminophenyldisulfide. Contact Dermatitis 1999; 41: 173-4.