120 An Evaluation of Uncertainty Within Control Banding Tools used for Occupational Exposure Assessment of Nanoforms and Nano-Enabled Products

Abstract

The use of control banding tools to aid in diminishing risks to nanomaterial exposure play an important part in early-stage risk assessment. With the inclusive nature of these tools, comes a certain amount of uncertainty with their findings, and uncertainty evaluation is an aspect which has scope for improvement in the current tools. The European Chemicals Agency provide three types of uncertainty to be assessed for chemical safety: Model uncertainty which relates to simplifications the model makes, Parameter uncertainty which relates to individual model parameters and Scenario uncertainty which is user dependent. To define possible improvements, the SAbyNA project has made investigations into Parameter uncertainty, and have used the Theory of Scales of Measurement, developed by Stevens. The identification of the measurement scale leads to the understanding of the permissible statistics (e.g., standard deviation) that can be performed with the data. To facilitate the assessment of the scale and the statistics, a check list was produced. Several control banding tools were analysed, and these tools employ ordinal scoring scales, which means that calculating average values and confidence intervals is not permissible. As evaluating the uncertainty in results greatly helps the exposure assessment, because it would describe the “quality” of the data and allow definitive comparisons among each other, it is recommended to improve the quantitative exposure estimation through sampling methods to get more measurements, which are beneficial for the uncertainty evaluation and for which the uncertainty can be evaluated according to the Guide to the expression of uncertainty in measurement.