Cobalt(2+) C3/C10 carboxylates salts

Endpoint summary

Description of key information

Skin irritation / corrosion: No adverse effect observed (not irritating)
Eye irritation / corrosion: Adverse effect observed (irritating)

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)

Additional information

Justification for selection of skin irritation / corrosion endpoint:
Salt reaction of cobalt (2+) and C3/C10 carboxylates composition is a combination of cobalt (2+) propionate and neodecanoic acid cobalt salt tested for skin and eye irritation. Conclusions of the studies carried out on these 2 compounds can thus be used as worst case scenario for the Salt reaction of cobalt (2+) and C3/C10 carboxylates.
Reliable in vivo skin irritation study described in Kukulinski (2013) on neodecanoic acid cobalt salt (OECD 404, GLP compliant) and reliable in vitro skin irritation study described in Heppenheimer (2010) on cobalt (2+) propionate (OECD 439, GLP compliant) are considered to be reliable without restrictions. The Salt reaction of cobalt (2+) and C3/C10 carboxylates was thus determined to be not irritating for the skin.

Justification for selection of eye irritation endpoint:
Salt reaction of cobalt (2+) and C3/C10 carboxylates composition is a combination of cobalt (2+) propionate and neodecanoic acid cobalt salt tested for skin and eye irritation. Conclusions of the studies carried out on these 2 compounds can thus be used as worst case scenario for the Salt reaction of cobalt (2+) and C3/C10 carboxylates.
Two reliable in vivo study described by Sanders (2012) and Arcelin (2011) (OECD 405; GLP complaint) are considered to be reliable without restrictions. Based on Arcelin study result considered as worst case scenario, the Salt reaction of cobat (2+) and C3/C10 carboxylates was thus determined to be irritating to the eyes.

Effects on eye irritation: irritating

Justification for classification or non-classification

Skin corrosion:

Two reliable in vitro studies described by Heppenheimer are considered to be reliable without restrictions and will be used for classification.

The overall irritation results in in-vitro human skin model tests (according to OECD 431; GLP compliant) are as follows:

- Neodecanoic acid cobalt salt:

- relative viability 3 min after treatment: 108.1 %

- relative viability 60 min after treatment: 45.7 %

- Cobalt(2+) propionate:

- relative viability 3 min after treatment: 84.4 %

- relative viability 60 min after treatment: 57.9 %

The classification criteria according to Regulation (EC) 1272/2008 as corrosive to skin are not met since the relative viability after 3 and 60 minutes exposure was above 50 % and 15% respectively, hence the 2 substances tested were determined to be not corrosive to the skin. Accordingly the substance salt reaction of Cobalt (2+) and C3/C10 carboxylates does not need to be classified as skin corrosive.

Skin irritation:

Two reliable in vitro studies described by Heppenheimer are available. The mean relative absorbances (% of the negative control, correlating with mean tissue viability) after 15 minutes incubation in the in-vitro human skin model test (EpiSkin, according to OECD 439; GLP compliant) were as follows for the 2 substances tested:

- Neodecanoic acid, cobalt salt: relative viability = 11.7%

- Cobalt(2+) propionate: relative viability = 71.2%

The neodecanoic acid cobalt salt was determined to be a skin irritant since the mean tissue viability was below the threshold for skin irritants of 50.0%, whereas cobalt(2+) propionate was determined not to be a skin irritant.

Testing requirements in other international schemes necessitated an in vivo test for neodecanoic acid cobalt salt (Kukulinski, 2013). Since in vivo test results should take precedence over in vitro test results, the results received from this in vivo test are taken forward for the chemical hazard assessment.

According to Kukulinski (2013) the overall irritation results 24, 48 and 72 hours after application per animal are as follows (according to OECD 404):

- erythema: 1, 2, 1.33

. oedema: 0.67 for all three animals

The classification criteria acc. to regulation (EC) 1272/2008 as irritating to skin are not met, since the values of erythema and oedema were below the threshold of ≥2.3 as well as the effects were fully reversible within 48 hours. 

Accordingly,the salt reaction of Cobalt (2+) and C3/C10 carboxylates will not be classified as skin irritant. 

Eye irritation:

Two reliable in vitro studies described by Heppenheimer are considered to be reliable without restrictions and will be used for classification.

The mean in-vitro scores after 240 minutes incubation results of the in vitro bovine corneal opacity and permeability assay (BCOP, according to OECD TG 437; GLP compliant) were respectively 0.00 for neodecanoic acid cobalt salt and 0.29 for cobalt(2+) propionate. The values were below the threshold for severe eye irritants of 55.1.

The classification criteria according to regulation (EC) 1272/2008 as severe eye irritation are not met, hence no classification required for the 2 substances tested. Accordingly the substance salt reaction of Cobalt (2+) and C3/C10 carboxylates does not need to be classified neither as corrosive nor severely irritating to the eyes.

Two in-vivo studies described by Arcelin (2011) and Sanders (2012) are also considered to be reliable without restrictions and will be also used for classification.

During the Sanders study, neodecanoic acid cobalt salt was applied to one eye of two animals each and the eye irritation was scored according to the Draize scale. The overall irritation results 24, 48 and 72 hours after application per animal are as follows:

- Corneal opacity= 0 for both animals

- Iris light reflex= 0 for both animals

- Conjunctival redness=0.67 and 0.33

- Conjunctival oedema (chemosis) = 0.33 and 0

The classification criteria according to Regulation (EC) 1272/2008 as irritating to eyes are not met for neodecanoic acid cobalt salt, since the values of conjunctival redness and chemosis were below the threshold of ≥ 2 as well as the effect was fully reversible within 48 hours and 72 hours, respectively.

According to Arcelin (2011) the overall irritation results 24, 48 and 72 hours after application of cobalt(2+) propionate per animal are as follows:

- Corneal opacity = 0.00 for all three animals

- Iris light reflex = 0.00 for all three animals

- Conjunctival redness = 1.67, 2.33, 2.00

- Conjunctival oedema = 0.00, 0.33, 0.00

The classification criteria according to Regulation (EC) 1272/2008 as irritating to eyes are met for cobalt(2+) propionate, since conjunctival redness was above the threshold of ≥2 as well as the effect were fully reversible within 7 days. Only in one animal conjunctival redness was not fully reversible within 14 days. The animal was further affected up to at least 14 days after treatment. The ocular findings consisted of scleral and conjunctival reddening as well as discharge (with mucus) and were considered as being a secondary effect (infection).

Thus, in a conservative approach, the salt reaction of Cobalt (2+) and C3/C10 carboxylates will be classified as eye irritant category 2 (H319).

Respiratory irritation:

The justification for classification as respiratory irritant is covered under the endpoint specific target organ toxicity- single exposure: inhalation as given in the acute toxicity section.