Hexachloroiridic acid

Sensitisation data (human)

Administrative data

Endpoint:

sensitisation data (humans)

Type of information:

other: Occupational, observation

Adequacy of study:

key study

Study period:

Observation reported from 1984-1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Case report on only one individual.

Data source

Reference

Reference Type:

publication

Title:

Contact urticaria with anaphylactic reactions caused by occupational exposure to iridium salt

Author:

Bergman A, Svedberg U and Nilsson E

Year:

1995

Bibliographic source:

Contact Dermatitis 32, 14-17

Materials and methods

Type of sensitisation studied:

respiratory

skin

Study type:

case report

Principles of method if other than guideline:

Patch testing performed on an individual with occupational respiratory and skin symptoms.

GLP compliance:

no

Remarks:

GLP not relevant to this type of study

Test material

Test material information

Constituent 1

Reference substance name:

Hexachloroiridic acid

EC Number:

241-012-8

EC Name:

Hexachloroiridic acid

Cas Number:

16941-92-7

Molecular formula:

Cl6Ir.2H

IUPAC Name:

hexachloroiridium(2-);hydron

Test material form:

other: 25% stock solution was diluted with deionised water containing NaCl and NaHCO3, final pH 7.5-8.0

Details on test material:

- Name of test material (as cited in study report): Iridium chloride
- Molecular formula (if other than submission substance): H2IrCl6
- Substance type: Technical product
- Physical state: In solution
- Analytical purity: no data
- Impurities (identity and concentrations): Measurements for 29 elemental impurities in the stock solution used for testing are reported, including those for rhodium, palladium, osmium and platinum. All are less that 200 ppm, except platinum (present at 310 ppm). "Insolubles" content of <1000 ppm.
- Composition of test material, percentage of components: no data
- Lot/batch No.: no data
- Expiration date of the lot/batch: no data
- Stability under test conditions: no data
- Storage condition of test material: no data

Method

Type of population:

occupational

Ethical approval:

not specified

Subjects:

- Number of subjects exposed: 1
- Sex: male
- Age: 26
- Race: "white"

Clinical history:

- History of allergy or causistics for study subject: no previous "medical record" [presumably no previous clinical history], no personal or family history of atopy, non-smoker.
- Symptoms, onset and progress of the disease: After 3 years of work, the patient developed a congested nose, rhinitis, a tendency to nasal ulceration, dyspnea [shortness of breath], a dry cough and eye irritation while at work. After around 2 years, the respiratory symptoms became worse to the extent that sporting activities were not possible in the evenings after work days (physical exercise without respiratory problems could be performed on non-working days). Occasional development of urticaria on the wrists around 5 minutes after direct skin contact with coating solutions [see below, under "Exposure history"] then began to occur, and periodically, urticaria also appeared at various friction sites such as the waist and ankles; this receded within hours after cessation of exposure.
- Exposure history: Employment as a process operator in an electrochemical factory manufacturing titanium anodes, which were coated in various metal salts of the platinum group dissolved in hydrochloric acid. The coating solution was sprayed onto the anodes automatically. The workplace had "insufficient ventilation" and poor enclosure of the process equipment, and so aerosols were able to spread into the working zone of the operators. Operators' skin could be exposed to the coating solution during repair of the supply lines to the spray mechanism. The major air contaminants were thought to be hydrochloric acid and "metal salts".
- Aggravating factors both in home and workplace: None reported.
- Family history: No family history of atopy.
- Medical history (for respiratory hypersensitivity): None
- Any other allergic or airway disorders: None
- Smoking history: Non-smoker

Controls:

14 workers at the same factory expsoed to salts of the platinum group metals (5 reported a tendency to occasional work-related nasal ulceration, 4 reported uncharacteristic skin symptoms (not contact urticaria), 3 reported varying degrees of nasal congestion and occasional work-related respiratory symptoms, 9 reported no symptoms). None exhibited skin reactions when prick-tested with an iridium salt [presumably hexachloroiridic acid]; 2 with the "most pronounced symptoms" underwent scratch tests with an iridium salt [presumably hexachloroiridic acid] - again no skin reactions were seen.

Route of administration:

dermal

Details on study design:

TYPE OF TEST(S) USED: prick test; also a skin test to the highest test concentration

ADMINISTRATION
- Type of application: by pricking and to the skin (without pricking) for the highest test concentration only
- Vehicle / solvent: water with sodium chloride and sodium bicarbonate buffer to result in a pH of 7.5-8.0
- Concentrations: 0.26 ng/ml to 0.5 mg/ml
- Volume applied: No data
- Testing/scoring schedule: After 15 minutes
- Removal of test substance: no data

EXAMINATIONS
- Grading/Scoring system: observation; measurement of weal and flare where appropriate

Results and discussion

Results of examinations:

SYMPTOMS
- Frequency, level, duration of symptoms observed: The highest prick test concentration produced a weal (4 mm) and flare (30 mm); the next concentration down (0.05 mg/ml) produced erythema (10 mm); lower concentrations produced no reaction. The skin test (without pricking) produced 4 "follicaular urtications" surrounded by a flare (20 mm).

RESULT OF CASE REPORT: The prick/skin-test reactions and occupational symptoms were considered indicative of allergy (possibly Type I hypersensitivity) to hexachloroiridic acid. Symptoms disappeared upon cessation of employment in the factory.

OTHER RESULTS: Hypersensitivity to the platinum impurity in the iridium-based test solution was discounted by skin prick tests with diammonium hexachloroplatinate solution - platinum concentrations were >1000 times that in the iridium test solution that had previously produced a reaction indicative of sensitisation. No reaction was seen.

Applicant's summary and conclusion

Conclusions:

A published paper describes a case of hypersensitivity to hexachloroiridic acid (in the absence of sensitisation to platinum), following occpational exposure.

Executive summary:

A published paper describes an individual exhibiting occupationally-related respiratory and skin symptoms. He had been employed for several years as a process operator in an electrochemical factory manufacturing titanium anodes and was exposed to airborne aerosols of metal salts of the platinum group and hydrochloric acid. Prick and skin testing with various concentrations of hexachloroiridic acid indicated hypersensitivity (in the absence of sensitisation to platinum).

Cessation of employment resulted in the disappearance of symptoms. The investigators diagnosed probable Type I allergy to this iridium salt.