pH and Reserve Acidity (Alkalinity) in the Toxicological Evaluation of Chemicals: Problems and Solutions
Abstract
In order to identify problems arising in the measurement of pH, reserve acidity (alkalinity) (RAA) and their application for toxicological evaluation of chemicals in terms of skin corrosion/irritation and serious eye damage/eye irritation, the standards developed for these purposes and implemented in the EAEU member states were analyzed. pH of model solutions of acids and bases was determined by the calculation method. When measuring pH, there are limitations associated with the physical state of chemicals, their composition and the functioning of the glass electrode. In some cases, the use pH and RAA for the classification of chemicals is difficult. The concentration of the solution (1%) in which pH of chemicals is often measured does not correspond to the concentration in which chemicals are marketed (100%). The use of the non-additive approach is limited by the lack of data on the concentrations of acids and bases at which their solutions reach extreme pH (≤ 2 or ≥ 11,5). Acids and bases often exhibit their necrotizing effect at concentrations noticeably higher than the limit set by the non-additive approach (1%). RAA values determined by standard method cannot be used for toxicological evaluation of chemicals, and extensive validation of this criterion has not been carried out. In order to optimize the use of pH and RAA for toxicological evaluation of chemicals, it is proposed: to include in the standards the method of measuring pH of gaseous chemicals; to determine the pH of chemicals sequentially in solutions with concentration of 1%, 10%, 100%; to reconsider the feasibility of taking into account the pH of components within the non-additive approach, implementing the use of specific concentration limits; to modify the method of determining RAA and to validate this criterion for mixtures.
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