Sulphamidic acid

Endpoint summary

Description of key information

Sulphamidic acid is irritant to skin and eyes.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Several studies are available investigating effects of sulphamidic acid to skin and eyes.

Therefore, the studies were assessed and used in a weight of evidence approach to assess the corrosion/irritation potential towards skin and eyes:

Skin corrosion/irritation

In six experimental studies using rabbits the potential for skin irritation was investigated. Whereas M.F.S. in 1962 investigated the effect of pure sulphamidic acid (0.5 g applied, moistened with 0.1 ml of water) without coverage, finding a moderate irritation of 2.6 (max. score 10), the effect was clearly stronger to abraded skin. Edwards in 1977 investigated granular and crystalline sulphamidic acid independently, using a DOT (US Department of Transportation) protocol, allowing the distinction of corrosive and non-corrosive material, and found sulphamidic acid being non-corrosive (in both forms, crystalline and granular when applied occlusive), although sulphamidic acid is considered a strong acid.

Leist et al. in 1978 investigated sulphamidic acid for skin corrosion/irritation potential according to EPA guideline OPPTS 870.2500 by applying sulphamidic acid unchanged, dissolved in physiological saline solution and as 15% aqueous solution (all occlusive). Whereas unchanged sulphamidic acid showed a very weak response, the response of skin when sulphamidic acid was applied in physiological saline or 15% aqueous solution, was remarkable stronger but still weak to moderate, typically not leading to classification as a skin irritant.

However, as no concentrated solutions have been tested and the study in 1962 (M.F.S.) was using open application to the skin, skin irritation at higher concentrations is expected. This is supported by public assessments provided by INRS (French Fiche Toxicologique) as well as the harmonised classification according to CLP, both stating sulphamidic acid being an irritant to skin and eyes.

Eye damage/irritation

Three studies investigating the effects of sulphamidic acid to eyes could be identified. Ambrose et al. published in 1943 his investigations in which he applied a 4% aqueous solution (pH = 0.82) to the conjunctival sac of rabbit eyes. At this time, no scoring tables were used for assessment and the results are only reported qualitatively as causing moderate degrees of conjunctivae and edema. When ammonium sulphamate (sulphamidic acid neutralised by ammonia with a pH of 4.82) was applied the same way, no irritation was seen.

In 1962 the Haskell Laboratories (M.F.S.) investigated the effect of sulfamic acid, which was sprinkled to the surface of the eyes (unchanged powder) of one albino rabbit. Within 72 hours corneal opacity, iritic inflammation and conjunctival effects Redness) were observed combined with swelling of lids to partially to half closed. The conclusion was to label the substance for eye irritation following these test results.

Finally, Edwards et al. in 1977 applied 0.1 mL sulphamidic acid (unchanged) to the eyes of two rabbits. One of the rabbits received eye washing after 20 seconds whereas the second one did receive no eye washing. In both animals no iritis was seen. Effects to cornea were reported as minimal injury (non washed) and localized minimal injury (washed). Conjunctivae effects noted were mild to minimal redness and swelling for 3 days.

In summary, all reports are rather old and pre-date OECD guideline protocols. Thus, their reliability is non-assignable as the reports are limited in detail and scoring. However, they do report consistently eye irritating effects of low severity and thus it can be concluded that sulphamidic acid is irritating to eyes.

 

No studies on respiratory irritation are available

 

Disregarded study

Ambrose reported findings for skin irritation/corrosion and was investigating the effects of 4% aqueous sulphamidic acid to rat skin when injected subcutaneously. Whereas sulphamidic acid produced extensive necrosis to rat skin at the site of injection, no irritation, inflammation or necrosis was observed, when a 4% aqueous solution of ammonium sulphamate (neutralized sulphamidic acid of pH 4.82) was applied. Thus, the effect is mainly attributable to the low pH and not untypical for mineral acids when injected subcutaneously. Due to the unrealistic exposure pattern of the test, the study results however are not suitable for classification and risk assessment for workers or consumers. 

 

Results with humans

Ambrose reported upon the effects of 4% aqueous sulphamidic acid (pH 0.82) to human skin when applied to the anterior surface of one arm. Whereas sulphamidic acid produced slight irritation to human skin, no irritation, inflammation or necrosis was observed at the second arm of the human subjects which were treated with 4% aqueous solution of ammonium sulphamate (neutralized sulphamidic acid of pH 4.82) accordingly. Thus, although such a low pH would usually lead to more severe effects, the substance sulphamidic acid at a concentration of 4% (aqueous) apparently only induced slight irritation to human skin.

In summary, the substance sulphamidic acid is considered an irritant to skin and eyes according to CLP (Regulation EC No 1272/2008).

Justification for selection of skin irritation / corrosion endpoint:
weight of evidence approach

Justification for selection of eye irritation endpoint:
weight of evidence approach

Effects on skin irritation/corrosion: irritating

Effects on eye irritation: moderately irritating

Justification for classification or non-classification

The sulfamic acid should be classified as skin irritant 2 and eye irritant 2 according to regulation (EC) NO 1272/2008 of the European Parliament and of the Council of 16 December 2008., Accordingly, the substance is classified Xi, R36/38 according to DSD (Directive 67/548/EEC). Classification for respiratory irritation is not possible due to lack of data.