Prediction of eye irritation potential of liquid and granular laundry detergent formulas using the bovine corneal opacity and permeability (BCOP) assay

Evaluation of eye irritation potential is a routine part of consumer product testing. Increasingly, companies are using in vitro methods to perform these assessments. We have used the bovine corneal opacity and permeability (BCOP) assay for the prediction of eye irritation of liquid and granular laundry detergent formulas. The BCOP assay was selected because it can distinguish between moderate and severe irritants as required to evaluate these classes of formulations. Corneas were maintained in short-term culture and the exposure conditions were optimized using marketed product upper-end benchmark formulas for each product class. The primary endpoint was the loss of epithelium as measured by the change in permeability of the cornea to fluorescein and was complemented by histological evaluation of depth of injury. The opacity endpoint was not used, as the surfactants in these products do not induce opacity in proportion to the depth of injury induced. Liquid laundry detergents were diluted to 25% and exposed to the corneas for 20 min while the granular detergents were diluted to 10% and exposed for 30 min. These conditions were selected for each product type to induce OD490 values in the midrange (between 0.5 and 0.6 absorbance units) and so increased or decreased irritation potential in the test formulas could readily be observed. Seventeen liquid and eleven granular laundry detergents were tested and the OD490 values ranged from 0.278 to 2.193 for the liquid detergents and 0.267 to 0.856 for the granular detergents. Histological changes in the epithelium and stroma were consistent with the OD490 values. These data suggest that the OD490 provides an effective measure of epithelial cell loss (degree of cell lysis) and thus irritation potential for these surfactant-based formulas. The upper-end benchmark set a known upper range for acceptable irritation for the product class. Those formulas inducing lower OD490 values may be considered to fall within the acceptable range while those inducing greater OD490 values should receive further evaluation and perhaps reformulation.