. 2013 Dec 28;88(3):701–723. doi: 10.1007/s00204-013-1156-8

Table 2.

Classification rules defined by UN GHS (UN 2013) and EU CLP (EC 2008)

Endpoint	Range scores^a	Category 2^b	Category 1^c
Endpoint	Range scores^a	Reversible effects on the eye/eye irritation	Irreversible effects on the eye/serious damage to eyes
CO	0–4	1 ≤ CO^Maj < 3; and/or	CO^Maj ≥ 3; and/or
IR	0–2	1 ≤ IR^Maj ≤ 1.5; and/or	IR^Maj > 1.5
CR	0–3	CR^Maj ≥ 2; and/or
CC	0–4	CC^Maj ≥ 2

CO^Maj, IR^Maj, CR^Maj, and CC^Maj: correspond to the second highest (for studies with 3 or 4 animals) or the third highest (for studies with 5 or 6 animals) of the mean CO, IR, CR, and CC scores (of gradings at 24, 48, and 72 h). UN GHS criteria (UN 2013) and the ECHA Guidance on the application of the CLP criteria for classification of studies with more than three animals (ECHA, 2012; chapter 3.3.2.3.2.2 In vivo data) were applied (i.e. 2 out of 3, 3 out of 4, 3 out of 5, or 4 out of six animals with a mean score above a classification cut-off)

CO corneal opacity, IR iritis, CR conjunctiva redness, CC conjunctiva chemosis

^aMean scores are calculated from gradings at 24, 48, and 72 h after instillation of the test material and used to determine the classification of the chemical based on CO^Maj, IR^Maj, CR^Maj, and CC^Maj

^bAll effects have to fully reverse within an observation period of normally 21 days. UN GHS provides the option to distinguish this single hazard category into two optional subcategories (not implemented in EU CLP): “Category 2A” (irritant to eyes) when any of the eye effects in any animal is not fully reversible within 7 days of observation (i.e. CO, IR, CR and/or CC > 0 at 7 ≤ day < 21); “Category 2B” (mildly irritant to eyes) when all observed eye effects are fully reversible within 7 days of observation (i.e. CO, IR, CR and CC = 0 at day 7 and beyond)

^cCat 1 also applies when CO = 4 or other severe reactions (e.g. destruction of cornea, discoloration of the cornea by a dye substance, adhesion, pannus, or interference with the function of the iris or other effects that impair sight) are observed at any time point in any rabbit during the observation period, and/or when effects that are not expected to reverse, or have not fully reversed within an observation period of normally 21 days (persistent effects) are observed (i.e. score > 0 on day 21 on any tissue in any animal)