Formulation effect on the dermal bioavailability of isothiazolone biocide

A central tenet of the science of toxicology is that the toxic effect of any material monotonically increases with the amount of the material delivered to the target tissue. This is the so-called dose-response relationship. Previous work is discussed in which a dose-response relationship is established for the induction and elicitation of cutaneous contact allergy from the isothiazolone biocide which is a 3 to 1 mixture of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one. The commercial product name for this mixture is Kathon LX biocide. Given a tissue dose-response, this current work determines and demonstrates a difference in risk from aqueous formulations with and without polymer. A lower delivered dose of biocide goes into the skin from an aqueous-based polymeric emulsion or paint than from an aqueous solution or oil-in-water emulsions without polymer. Thus, the estimate of risk, as a direct result of dose, and the determination of a safe use level of a biocide in any particular formulation matrix need to incorporate this reality.