Investigations on Reducing Ocular Irritation Associated with Harsh Ingredients by Altering Physicochemical Properties of the Formulation
With the upcoming implementation of the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) in various forms throughout the world and a global movement towards a reduction in animal testing, more emphasis is placed on utilizing the inherent hazards of chemicals for classification and labeling; however, the assessment of the toxicity of chemical mixtures, particularly ocular irritation, can be complex. The ability to formulate mixtures to be less irritating with minor modifications to the physical form would be very beneficial. The present study used the Bovine Cornea Opacity and Permeability (BCOP) assay, which is an OECD-approved in vitro method to assess ocular irritation, to investigate how physical properties (e.g., viscosity) affect ocular irritation. We found that the BCOP in vitro scores of irritating chemicals from several classes, including strong bases, were diminished by altering the viscosity of the aqueous medium or by dosing the solution as a foam. Our data show that a 1% NaOH solution in water produced an in vitro score of 165; however, when the medium was thickened with 1% Carbopol®, the in vitro score dropped to 67.6. A change of this nature is significant, and if this were an EPA-registered antimicrobial cleaner, for example, this reduction in the BCOP score would lower the hazard category. Product form and usage can clearly impact exposure, and the present results suggest that modifications to the physical properties of chemical mixtures can alter their ocular irritation potential; perhaps by affecting exposure to the eye. Although no formal comparisons were performed in animals, the BCOP assay is an OECD-validated method to assess ocular irritation, and studies have shown that the BCOP assay does not under-predict the results of traditional animal tests; thus, there are no obvious reasons to suggest that the present results would not correlate to animals or humans.