School backpacks and commuter bags: A non-negligible source of human exposure to phthalate monoesters

Limited literature indicated the occurrence of phthalate monoesters within consumer products, although they have been generally recognized as exposure biomarkers or metabolic phthalate diesters. The potentiality of phthalate monoesters as contaminants in consumer products is not yet adequately addressed. To fill this knowledge gap, the present study examined the occurrence of phthalate diesters, alternatives, and monoesters, in school backpacks and commuter bags. Fabrics in 21 of 24 backpacks and 23 of 32 commuter bags simultaneously contained target contaminants. The levels of monoesters (nd-18; median: 1.1 μg g^-1) were three orders of magnitude lower than those of diesters (nd-34000; median: 690 μg g^-1) and alternatives (nd-15000; median: 160 μg g^-1), and were highest in bags with vinyl-based coatings across all texture types and greater on the backside than on the front coatings. Secondary oxidation phthalate monoesters were detected for the first time in the bag products. Commuter bags contained higher levels of the target contaminants than school backpacks. The estimated exposure doses from dermal absorption and hand-to-mouth ingestion of target analytes in rear-coated commuter bags for consumers exceeded those from indoor dusts in the literature. Users of backside-coated commuter bags via inhalation, dermal contact absorption and hand-to-mouth/lip behavior were potentially under threat of non-carcinogenic risk (HQ ≥ 1), while school backpack and front/non-coated commuter bag users experienced insignificant risk. These results indicate that commercial bags, particularly those with softened plastic coatings, could be a non-negligible source of human exposure, and it is advisable to prioritize coating-free products to mitigate potential health risks.