Butyric acid

Endpoint summary

Description of key information

In two primary skin irritation tests according or similar to OECD test guideline 404, butyric acid was demonstrated to be corrosive on basis of EU regulations.
In a primary eye irritation test comparable to OECD test guideline 405, butyric acid was demonstrated to be corrosive on basis of EU regulations.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (corrosive)

Eye irritation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (irritating)

Additional information

Skin irritation

 

Two valid studies are available to assess the skin irritating potential of butyric acid.

 

Hoechst AG, Rupprich 1983 (key study)

 

In a valid GLP OECD 404 study, 3 rabbits were exposed dermally to a single dose of 0.5 mL of undiluted butyric acid for a period of one hour .Butyric acid was corrosive as evidenced by skin lesions, severe hardening and discoloring which persisted until the end of the 14 day observation period (Hoechst AG, 1983).

 

Celanese, Ebbens 1972

 

In a primary skin irritation test (DOT test), six adult albino New Zealand rabbits were dermally exposed to 0.5 mL of butyric acid for 1 hour. Irritation was scored at 1, 24 and 72 hours by a grading system similar to Draize/OECD TG 404. The animals showed deep chemical burns over the entire site at all observation time points. Observation was terminated after 72 hours (Celanese, 1972).

 

Based on present EU regulations, butyric acid is corrosive as evidenced by deep skin lesions at all observation time points, which were not reversible.

 

Eye irritation

 

One valid study is available to assess the eye irritating potential of butyric acid.

 

BASF AG 1978

 

In a primary eye irritation test, 50 µL of butyric acid (purity 99%) was instilled into the conjunctival sac of one eye each of two male Vienna White rabbits. Animals then were observed for 8 days. The original irritation readings were converted to the Draize score at a later date. Readings were taken 24 h, 48 h, and 8 d after application of test substance.

 

The treated eyes showed severe opacity and chemosis, which persisted until the end of the observation period (8 d) with no tendency to subside.

 

In this study, butyric acid was tested to be corrosive to the eye (irreversible effects on the eye - Category 1) based on the irreversibility of the effects observed.

 

This pre-guideline study bears some deviations from present test guidelines (amount of test substance, observation period, time of irritation score readings). Nevertheless, the data are assessed to be sufficiently valid to represent the eye damaging potential of butyric acid, as the correct amount of test substance would result in even more pronounced effects. Using available results conforms to the tiered testing and evaluation strategy for eye irritation/corrosion and further testing can be avoided.

Effects on skin irritation/corrosion: corrosive

Effects on eye irritation: corrosive

Justification for classification or non-classification

Due to the irreversible corrosive effects of butyric acid to the skin and the eye of rabbits, it has to be classified as skin corrosive Category 1 and as causing irreversible effects on the eye (Category 1).