Product Use Categories, or PUCs, are identifiers assigned to products in ChemExpo, indicating the type of product assigned to each data record based on information provided in the original data source. There are three kinds of PUCs: Formulation, Article, and Industrial/Occupational PUCs, which organize PUCs based on the regulatory guidelines regarding the manufacture and ingredient reporting requirements for the products. The organizational Hierarchy for PUCs consists of three levels: General Category, Product Family, and Product Type. PUCs are organized from general to more specific product types, i.e., ‘Personal care’ is the most general category, while ‘Personal care – dental care – toothpaste’ would be a specific product type. Products are curated to Product Use Categories through various manual and automated (natural language processing-based) assignment methods, referred to as Classification Methods. The level of confidence in the assignment method may vary based on how much detail is provided to the curator at the time of assignment. More information on the development of the PUC categories can be found in Isaacs et al. (2020). See User Guide Section 'Explore Products or Product Use Categories' for more information.