Chemical ingredients in personal care products and their hormetic effects on freshwater photobacteria

Personal care products (PCPs), including skin lotions, toners, and make-up waters, are ubiquitous in daily life. Prior research has demonstrated hormesis, a biphasic dose-response phenomenon, in these PCPs on the freshwater photobacterium Vibrio qinghaiensis sp. -Q67 (Q67). Given that PCPs contain various active chemical components, their hormetic effects are intricately linked to these ingredients. However, studies focusing on the concentration-response relationships of individual PCP chemical ingredients are scarce. Building upon our previous work, we analyzed the ingredients of 6 PCPs and employed Q67 as a model organism to investigate the concentration-response relationships of these ingredients. Our analysis of 6 representative PCPs revealed 49 chemical ingredients, categorized into 10 moisturizers, 5 preservatives, 5 emulsifiers, 5 emollients, 20 ingredients with known efficacy, and 4 with unknown efficacy. Among these 49 chemical ingredients, 30 water-soluble ones were suitable for toxicity testing. At 0.25 h, 23 chemical ingredients exhibited S-shaped concentration-response curves (CRCs) with EC50 values spanning from 6.943E-5 g/mL [lactic acid (LAA)] to 1.032 g/mL [sorbitol (SBO)], while 2 [PEG-7 glyceryl cocoate (PGC) and Tween 80 (TW80)] showed hormesis with J-shaped CRCs, and 5 [adenosine (ADE), dexpanthenol (DEX), E4C, E6C, serine (SER)] lacked discernible CRCs. At 12 h, 13 chemical ingredients displayed S-shaped CRCs with EC50 values ranging from 4.402E-5 g/mL (E6C) to 1.961E-1 g/mL [dicaprylyl carbonate (DIC)], while 16 showed J-shaped CRCs, with EC50, zero effective concentration point (ZEP), ECmin, and Emin values indicating a consistent variation range spanning 4 orders of magnitude. These findings underscore the importance of considering individual chemical ingredients in assessing the risks associated with PCPs.