What does "low exposure" mean? Exposure considerations in the testing of notified new substances

In the notification procedure for new substances, the need to conduct further toxicity tests may arise if the outcome of a qualitative or quantitative risk assessment indicates relevant risks. Sometimes a quantitative assessment is not possible (e.g., if a no observed adverse effect level [NOAEL] is not available). A different approach is required for such substances. An approach based on the correlation of the classification of the substance (the possible outcome of testing) with the assumed tolerable exposure levels is presented here. It relates to the hazard band model developed by the Health and Safety Executive (HSE) of the United Kingdom. To aid decision-making, the assumed tolerable exposure level is compared with the estimated workplace exposure level by means of calculating the quotient of these two figures. The quotient is called the assumed margin of safety (AMOS). A quotient higher than 1 means that testing may be deferred. The approach is described for a powdery substance used as a pigment in the coloration of plastics and rubber. Depending on the exposure situation, the need for further testing to determine the repeated dose toxicity of the substance is discussed.