2,2'-azobis[2-methylpropionamidine] dihydrochloride

Sensitisation data (human)

Administrative data

Endpoint:

sensitisation data (humans)

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Remarks:

Publication on clinical observation and patch test with AAPH in 8 patients exposed to AAPH and 6 healthy volunteers only, no quantitative information on the purity.

Data source

Reference

Reference Type:

publication

Title:

Contact dermatitis due to 2,2'-azobis(2-amidinopropane) dihydrochloride: an outbreak in production workers.

Author:

Takiwaki H, Arase S, Nakayama H.

Year:

1998

Bibliographic source:

Contact Dermatitis 39; 4-7

Materials and methods

Type of sensitisation studied:

skin

Study type:

other: patch test in production worker and healthy volunteers

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Patch tests were carried out with AAPH 1% and 5% aq. (in addition to several other test substances, which are not relevant to report here) on 8 male workers (aged 43-51 years) engaged in AAPH production, who complained of itchy eruptions on their hands and other locations lasting for a few months. Patch tests for AAPH were also performed on 6 healthy volunteers who had never been exposed to AAPH.
The miniplaster with which allergens were discoverd was used as the patch testing device to reduce the distress to the patients. Patches remained on the back for 2 days and were read at 2, 3, 7 and 14 days using ICDRG scores.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

2,2'-azobis[2-methylpropionamidine] dihydrochloride

EC Number:

221-070-0

EC Name:

2,2'-azobis[2-methylpropionamidine] dihydrochloride

Cas Number:

2997-92-4

Molecular formula:

C8H18N6.2ClH

IUPAC Name:

2,2'-diazene-1,2-diylbis(2-methylpropanimidamide) dihydrochloride

Details on test material:

- Name of test material (as cited in study report): AAPH

Method

Type of population:

other: production workers

Ethical approval:

not specified

Subjects:

production workers involved in AAPH production,
8 workers with signs of contact dermatitis

Clinical history:

production workers with itchy eruption on the skin:
none of them had any history of hand eczema or atopic dermatitis. Workers were obliged to wear rubber gloves whilst working.
On physical examination, the following laboratory tests were performed: complete blood count and differential cell count, automated blood chemistry analysis, IgE Radio Immuno Sorbent Test (RIST) and Radio Immuno Assay Test (RAST) for various allergens, erythrocyte sedimentation rate, and urinalysis.

Controls:

6 healthy volunteers who had never been exposed to AAPH.

Route of administration:

dermal

Details on study design:

Patch tests were carried out with AAPH 1% and 5% aq (in addition to several other test substnces, which are not relevant to report here) on 8 male production workers (aged 43-51 years), who showed itchy eruptions on their hands and other locations lasting for a few months. Patch tests for AAPH was also performed on 6 healthy volunteers who had never been exposed to AAPH.
The Miniplaster, with which allergens were discovered, was used as the patch testing device to reduce the distress to the patients. Patches remained on the back for 2 days and were read at 2, 3, 7 and 14 days using ICDRG scores.

Results and discussion

Results of examinations:

All patients showed positive reactions to both 1% and 5% AAPH at 2 and 3 days, while all control subjects showed negative results. No flare-up reaction was found at the test sites in all control subjects at 7 and 14 days. The results of patch tests at 3 days are summarized in Table 1.

The diagnosis of allergic contact dermatitis due to AAPH was made for all patients. The company discontinued the manufacture of AAPH, and the workplace was carefully cleaned with plenty of water. All working clothes, gloves, and rubber boots used by the production workers were discarded. All patients were treated with topical corticosteroids and oral antihistamines. On follow-up, it was found that, although the severity of the lessions was far milder, most patients still suffered occasional recurrences of hand dermatitis during the following 1-2 years. In 1 patient, dark brown, 1-2 mm diameter, sparse hyperpigmented macules developed on the palms after the eczematous lesions disappeared.

Any other information on results incl. tables

Table 1: Results of patch tests at 3 days

Patient No.		1	2	3	4	5	6	7	8	9-14 (control)
Age		46	51	44	43	46	44	49	49	37-56
AAPH	1% aq.	++	+	++	++	++	+	++	++	all -
AAPH	5% aq.	++	++	++	++	++	++	++	++	all -
TMTD	1% pet.	-	-	-	-	-	-	-	-
formaldehyde	5% aq.	-	-	?+	-	-	-	-	-
urushiol	0.01% pet.	-	-	+	+	++	++	++	+
NiSO4	5% aq.	+	-	+	++	-	-	-	-	NT
HgCl2	0.05% aq.	+	-	-	-	-	-	-	-
CoCl2	2% aq.	+	-	++	+	-	-	-	-
K2Cr2O7	0.5% aq.	+	-	?+	-	-	-	+	-
PPD	2% pet.	-	-	-	-	-	-	-	+

 

Discussion

 

All patients were engaged in the final production process of this chemical, and none of the workers who were exposed to either the raw materials or the intermediates formed during the chemical's synthesis complained of dermatitis similar to that seen in our patients. All patients showed strong positive reactions to AAPH on patch testing, and their dermatitis improved after the production of AAPH was discontinued. According to the manufacturer, the final product was highly purified and the concentrations of contaminants, if any, were considered to be quite low. Therfore, it is most likely that AAPH itself was the causative agent of the contact dermatitis in these patients, although allergy to other materials used in the production process or possible contaminants in the final product s cannot be strictly ruled out. From our investigations in this plant, contamination of protective rubber gloves, during scraping-out of products from the tanks for purification, was suspected as being causative of this occupational contact dermatitis. The reactions to AAPH were negative in all control subjects, indicating that this chemical probably acted as an allergen rather than as an irritant. This was also supported by the clinical observation that most patients suffered occasional eruptions for as long as 1-2 years after production of AAPH had been discontinued. The recurrence of skin lesions may be due, at least in part, to contact with AAPH remaining in very small amounts in the workplace despite several rounds of cleaning.

Concerning the results of patch testing for materials other than AAPH, many patients showed positive reactions to urushiol, nickel, and cobalt. It is not surprising that 6 out of 8 patients were allergic to urushiol, because there are numerous urushi plants in the woods and forests in this part of Japan, and the rate of positive reaction to urushiol in standard patch testing is reported to be about 80% for patients with dermatitis in this region. There were no urushi plants in the factory yard, however, and Japanese lacquer made from urushi had not been used in this plant. The reason why so many patients showed a positive response to metal allergens such as nickel is unclear. Some of the positive or weakly positive reactions in case nos. 1 and 3 may be due to the "excited skin syndrome", as both patients showed positive responses to many allergens. Metal-containing chemicals were not used in the synthesis of AAPH. However, as all patients had been engaged in the production of various chemicals before the manufacturer started to produce AAPH, they might have been sensitized to these allergens through their previous work.

Applicant's summary and conclusion

Conclusions:

In 8 workers of a chemical plant with itchy eruptions on the skin, a patch test with 1% and 5% of the substance showed positive reactions at day 2 and 3 in all patients, while control subjects showed negative results. The diagnosis of allergic contact dermatitis due to the substance was made for all workers.

Executive summary:

2,2’-azobis(2-amidinopropane) dihydrochloride (AAPH) is an azo compound which has been used as a radical chain initiator. The purpose of this study was to confirm contact sensitivity to AAPH in individuals, who were engaged in the production of AAPH, and presented with prolonged eczematous eruptions, mainly on exposed areas. Patch testing was carried out with AAPH (1 and 5 % aq.) on 8 patients and 6 healthy volunteers who had never been exposed to this chemical. All patients showec a strong positive patch test reaction to this agent, while all control subjects showed negative results. Because this chemical has recently been used for studies on the oxidation of biological material, not only production workers in the chemical industry but also medical researchers should avoid prolonged exposure to this agent.

 

2,2’-azobis(2-amidinopropane) dihydrochloride (AAPH) is a water-soluble radical chain initiator, which has been used not only in the chemical industry but also in the field of experimental medicine and biochemistry. In 1994, workers who were engaged in the production of AAPH in a chemical plant complained of itchy eczematous eruptions, mainly on exposed areas such as the hands and forearms. As a result of patch tests in these patients and control subjects, AAPH was confirmed to be the causative agent of this outbreak of contact dermatitis. As far as we are aware, this is the 1^streport of contact allergy to AAPH, except for an unpublished document.