Sodium carbonate

Endpoint summary

Description of key information

Several reliable skin irritation studies and 2 reliable eye irritation studies are available.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Skin

Non-human information

The non-human information on skin irritation of sodium carbonate has been described already on page 12 and 13 of the OECD SIDS dossier (2002). Please find hereafter the text:

In a study performed according to EPA 16 CFR 1500.3 guidelines, the skin irritation potential of sodium carbonate monohydrate was examined in 6 New Zealand White rabbits (Rinehart, 1978c). Each rabbit had two patches clipped for hair, one abraded and one left intact. An amount of 0.5 g was applied as an 1 g/ml aqueous slurry, and covered by an occlusive patch for 24 hrs. It is not reported whether the area was cleaned when the patches were removed. The average erythema and oedema score was 0, and the Primary Dermal Irritation Index 0. A skin irritation study was performed with six New Zealand White rabbits (Chibanguza, 1985a). A quantity of 0.5 g sodium carbonate was applied to intact and abraded skin (6.25 cm2) and covered with an occlusive bandage for 4 hours. After this period the skin was washed. Thirty min, sixty min, 24, 48 and 72 hours after exposure no signs of erythema or oedema were observed. The method used in this study was comparable to OECD guideline 404.

In addition to the two valid guideline studies mentioned before, another skin irritation test was done which was not documented in sufficient detail. An aqueous solution of sodium carbonate (50% w/v) was applied to the skin (intact and abraded) of six rabbits and six guinea pigs for 4 hours (Nixon et al., 1975). The animals were examined at 4, 24 and 48 hours after application of the solution for erythema and oedema. The abraded skin of the rabbits had slight erythema and oedema, and those of the guinea pigs were negligibly affected. There were no signs of erythema or oedema in the intact skins.

Six New Zealand rabbits were exposed to sodium carbonate monohydrate to assess the dermal LD50(Rinehart, 1978b). Thirty percent of the body surface area was exposed to 2,000 mg/kg bw, administered as an aqueous slurry with concentration 1,000 mg/ml. Three animals had abraded skin and 3 animals had non-abraded skin. After 24 hrs of occluded exposure, the test area was wiped clean. Well-defined to severe erythema and slight to severe oedema were observed in all six animals 24 hours after compound administration.

 

Human information

The human information on skin irritation of sodium carbonate has been described already on page 13 of the OECD SIDS dossier (2002). Please find hereafter the text:

A human patch (skin irritation) test with 98% sodium carbonate was performed using 26 human volunteers and exposing them for 15, 30 or 60 minutes through to 2, 3 and 4 hours (York et al., 1996). The patch test involved the application of 0.2 g on to a plain Hill Top Chamber and treated sites were assessed 24, 48 and 72 hours after patch removal. The results showed no reactivity among the volunteers and therefore these solutions of sodium carbonate were not classified as irritant based on the human patch test.

An aqueous solution of sodium carbonate (50% w/v) was applied to the skin (intact and abraded) of six human volunteers for 4 hours (Nixon et al., 1975). The volunteers were examined at 4, 24 and 48 hours after application of the solution for erythema and oedema. Categorisation of irritancy to human skin was based on the Primary Irritation Index (PII). The abraded skin had erythema and oedema (mean score > 2) with two subjects having a maximum grade than 4. There were no signs of erythema or oedema in the intact skins (mean PII >1.0).

 

Eye
Non-human information

The non-human information on eye irritation of sodium carbonate has been described already on page 13 and 14 of the OECD SIDS dossier (2002). Please find hereafter the text:

The ocular irritation potential of sodium carbonate monohydrate was assessed in a study performed on 9 New Zealand rabbits (Rinehart, 1978d). A volume of 0.1 ml was instilled in one eye of each animal. After approximately 4 seconds the treated eyes of 3 rabbits were rinsed with 30 ml distilled water, while the remaining rabbit's eyes were not irrigated during the 14 days observation period. Among the animals with unwashed eyes, 2 suffered ruptured eyes and the remaining 4 still had signs of irritation at the termination of the study. One of the animals with washed eyes had signs of irritation at the termination of the study, while the exposed eye appeared normal in the remaining 2 animals from day 2 and 14, respectively. According to the scoring system employed by the authors of the study the responses were either positive or negative. 6/6 animals with unwashed eyes had a positive cornea score, iris score, conjunctivitis (redness and chemosis) score. Among the animals with washed eyes 1/3 rabbits had a positive cornea score, iris score and conjunctivitis

(redness and chemosis) score. Based on the results sodium carbonate was considered irritating for the eyes. The scoring system complied with the EPA 16 CFR 1500.42 guideline. It is to be noted that this scoring system is not comparable to the CLP criteria and hence, this study cannot be used for classification purposes.

An eye irritation study was performed with six New Zealand White rabbits (Chibanguza, 1985b). Ocular irritancy was tested by instilling 0.1 g sodium carbonate into the left eye (conjunctival sac) of each animal, the right eye served as the untreated control. After 1 hour, 24, 48 and 72 hours the eyes were examined for observations of the conjunctivae, cornea and iris. Ocular irritation was scored according to the scale by Draize. The mean Draize intensity score was for conjunctival redness 1.67, for conjunctival chemosis 1.38 and for the iris 0.25. The method used in this study was comparable to OECD guideline 405.

Ocular irritation of sodium carbonate was evaluated in two groups of at least six New Zealand albino rabbits (male and female) based on the methodology of Draize (Murphy et al., 1982). Sodium carbonate (0.1 ml) was administered to the right eye directly on the central portion of the cornea, the left eye served as the untreated control. The eyes of the first group of rabbits were rinsed for 2 minutes, 30 seconds after instillation (rinsed eyes), the eyes tested in the second group were not rinsed after instillation (unrinsed eyes). Control and treated eyes were scored at 1 h and 1, 2, 3 and 7 days after exposure according to the scale of Draize. Corneal opacities were produced in unrinsed eyes within 1 h after exposure to sodium carbonate and the severest effect was noted by day 3 (mean Draize intensity score 3.8), the severity was maintained through day 7. In rinsed eyes, corneal opacities were observed on day 2 (mean Draize intensity score 0.8) and had disappeared by day 7. Iritis was observed in unrinsed eyes at 1 h after exposure to sodium carbonate and a mean draize score of 2 was reported on days 1, 2, 3 and 7. In rinsed eyes, iritis was observed at 1 hr after exposure (mean Draize intensity score 1.0) and had disappeared by day 3 after exposure. Sodium carbonate produced conjunctivitis which lasted through day 7 in all animals tested. It also produced pannus in 6/12 unrinsed eyes and keratoconus in 2/12 unrinsed eyes. The method used in this study was mainly comparable to OECD guideline 405. Based on the results of the test sodium carbonate was considered highly irritating.

Summary and discussion of irritation

Skin: Several reliable skin irritation studies are available for sodium carbonate. The study by Chibanguza (1985) is identified as the key study. It is performed comparable to OECD guideline 404. This study did not reveal signs of erythema or oedema. Likewise, in the supporting studies, no or very slight irritation effects were observed. Based on these findings it can be concluded that sodium carbonate has no or a low skin irritation potential.

Eye:The available eye irritation tests revealed different results. Studies using a dose of 0.1 ml sodium carbonate monohydrate and sodium carbonate (anhydrous) resulted in a classification of irritating and highly irritating, respectively. Based on these results sodium carbonate was considered irritating for the eyes. The scoring system complied with the EPA 16 CFR 1500.42 guideline. It is to be noted that this scoring system is not comparable to the CLP criteria and hence, this study cannot be used for classification purposes.

However, based on the key study with a dose of 0.1 g sodium carbonate it was not classified as an ocular irritant.

In conclusion: based on the overall results and in line with the harmonized classification, sodium carbonate is considered irritating to the eyes.

 

Corrosivity

The results of the irritation studies indicate that sodium carbonate is non-corrosive.

Justification for classification or non-classification

Based on the available data, sodium carbonate has to be classified as eye irritant in accordance with EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No.1272/2008 (Eye Irrit. 2).