The magic number of "corrosive" vs. "irritation" appears to be if the damage is reversible after a 4 hr exposure. See pages II-4,5,6 for the formatted version. Included are subsets of corrosives and irritants.

This doesn't address using the "corrosive" definition as it applies to metals (implied by the GHS symbol). It also varies from the definition for "corrosivity" when applied to EPA hazardous waste characterization (pH less than or equal to 2 or greater than or equal to 12.5).

Jeff

Definition Skin corrosion means the production of irreversible damage to the skin following the application of a test substance for up to 4 hours. Criteria Substances and mixtures of this hazard class are assigned to a single harmonized corrosion category. Category1 1. For Substances and Tested Mixtures: • Human experience showing irreversible damage to the skin; • Structure/activity or structure property relationship to a substance or mixture already classified as corrosive; =E2=80=A2 pH extremes of < 2 and > 11.5 including acid/alkali reserve capacity; • Positive results in a valid and accepted in vitro skin corrosion test; or • Animal experience or test data that indicate that the substance/mixture causes irreversible damage to the skin following exposure of up to 4 hours (See Table 3.2.1) 2. If data for a mixture are not available, use bridging principles in 3.2.3.2. 3. If bridging principles do not apply, (a)For mixtures where substances can be added: Classify as corrosive if the sum of the concentrations of corrosive substances in the mixture is > 5% (for substances with additivity); or (b)For mixtures where substances cannot be added: =E2=89=A5 1% corrosive substance. See 3.2.3.3.4. For those authorities wanting more than one designation for corrosivity, up to three subcategories are provided within the corrosive category: Subcategory 1A - =E2=89=A4 3 minutes exposure and =E2=89=A4 1 hour observation; Subcategory 1B - >3 minutes =E2=89=A4 1 hour exposure and =E2=89=A4 14 days observations; and Subcategory 1C - > 1 hour and =E2=89=A4 4 hours exposures and =E2=89=A4 14 days observations.

Definition Skin irritation means the production of reversible damage to the skin following the application of a test substance for up to 4 hours. Criteria Substances and mixtures of this hazard class are assigned to a single irritant category. Category 2 1. For Substances and Tested Mixtures • Human experience or data showing reversible damage to the skin following exposure of up to 4 hours; • Structure/activity or structure property relationship to a substance or mixture already classified as an irritant; • Positive results in a valid and accepted in vitro skin irritation test; or • Animal experience or test data that indicate that the substance/mixture causes reversible damage to the skin following exposure of up to 4 hours , mean value of > 2.3 < 4.0 for erythema/eschar or for oedema , or inflammation that persists to the end of the observation period, in 2 of 3 tested animals (Table3.2.2). 2. If data for a mixture are not available, use bridging principles in 3.2.3.2. 3. If bridging principles do not apply, classify as an irritant if: (a) For mixtures where substances can be added: the sum of concentrations of corrosive substances in the mixture is > 1% but < 5%; the sum of the concentrations of irritant substances (Cat2) is > 10%; or the sum of (10 x the concentrations of corrosive ingredients) + ( the concentrations of irritant ingredients(Cat2)) is > 10%; or (b) For mixtures where substances cannot be added: =E2=89=A5 3% an irritant substance(Cat2). (See 3.2.3.3.4) For those authorities wanting more than one designation for skin irritation, an additional mild irritant category is provided: Category 3 1. For Substances and Tested Mixtures =E2=80=A2 Animal experience or test data that indicates that the substance/mixture causes reversible damage to the skin following exposure of up to 4 hours, mean value of > 1.5 < 2.3 for erythema/eschar in 2 of 3 tested animals (See Table 3.2.2) 2. If data for a mixture are not available and the bridging principles in 3.2.3.2. 3. If bridging principles do not apply, classify as mild irritant if: • For mixtures where substances can be added the sum of the concentrations of irritant substances(Cat2) in the mixture is > 1% but < 10%; • the sum of the concentrations of mild irritant substances(Cat3) is > 10%; • the sum of (10 x the concentrations of corrosive substances) + (the concentrations of irritant substances(Cat2)) is > 1% but < 10%; or • the sum of (10 x the concentrations of corrosive substances) + (the concentrations of irritant substances(Cat2)) + (the concentrations of mild irritant substances (Cat3)) is > 10%.

Jeff Lewin