Registration Dossier

Administrative data

Description of key information

According to the CLP Regulation Annex VI Table 3.1, the concentration limit for corrosivity of NaOH is considered to be 2%. Up to the most recent ATP, this has not been changed. Therefore, 2% is taken forward to the risk characterisation as concentration limit for corrosivity.

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

Four reports were available on skin irritation studies with rabbits. BASF (1978a) reported that a concentration of 0.95% was mildly irritating, while Kynoch et al. (1977a) reported that 1% was slightly irritating. According to BASF (1978b) a concentration of 4.9% was moderately irritating, while Kynoch et al. (1977b) reported that a concentration of 5% was irritating for 5 of 6 animals but corrosive for 1 of 6 animals. The corrosivity potential of NaOH was confirmed by an in vitro study (Stobbe et al., 2003).

Studies with human volunteers revealed that concentrations of 0.5 and 1 % were irritating (York et al., 1996; Dykes et al., 1995; York et al., 1996). A study with Caucasian volunteers showed that 2% NaOH was highly irritating (Fluhr et al., 2004).

Eye

Reliable eye irriation studies have been reported using rabbits as test species.

Several authors reported that low concentrations of NaOH did not result in eye irritation. According to Morgan et al. (1987) concentrations of 0.004; 0.04 and 0.2% NaOH are not irritating to the eye of rabbits. Murphy et al. (1982) found neither conjunctivitis nor iritis at concentrations of 0.1 and 0.2%. Jacobs (1992) observed no irritation at 1%.

Irritation of the eyes of rabbits was reported at NaOH concentrations of 0.4; 0.5; 0.95; 1; 2 and 3% (Jabobs, 1992; Morgan et al., 1987; Murphy et al., 1982; Reer et al., 1976). Corrosive effects were found at 1.2; 8 and 10% NaOH (Morgan et al., 1987; Reer et al., 1976; Wentworth et al., 1993).


Effects on skin irritation/corrosion: corrosive

Effects on eye irritation: irritating

Justification for classification or non-classification

- According to the CLP Regulation No 1272/2008 Annex VI Table 3.1, the concentration limit for corrosivity to the skin of NaOH is considered to be 2%

- According to the CLP Regulation No 1272/2008 Annex VI Table 3.1, NaOH is a skin corrosive category 1A at a concentration ≥ 5%

- According to the CLP Regulation No 1272/2008 Annex VI Table 3.1, the concentration range for eye/skin irritation is 0.5 % ≤ C < 2 %