Antimicrobial, preservative, and hazard assessments from eight chemical classes

Authors: Lynn, Lauren; Scholes, Rachel; Kim, Jong Heon; Wilson-Welder, Jennifer; Orts, William; Hart-Cooper, William

Submitted to: ACS Omega
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2024
Publication Date: 4/10/2024
Citation: Lynn, L.E., Scholes, R.C., Kim, J., Wilson-Welder, J.H., Orts, W.J., Hart-Cooper, W.M. 2024. Antimicrobial, preservative, and hazard assessments from eight chemical classes. ACS Omega. 9(16):17869–17877. https://doi.org/10.1021/acsomega.3c08672.
DOI: https://doi.org/10.1021/acsomega.3c08672

Interpretive Summary: Chemical preservatives are under increasing scrutiny for their human and environmental hazards. We describe the hazards and performance of next-generation, low-hazard preservatives and compare them to conventional ingredients.

Technical Abstract: Preservatives for consumer products, such as isothiazolinones and formaldehyde-releasing compounds, provide safety and stability in consumer products. Yet these ingredients also present human and environmental hazards including allergic contact dermatitis and acute aquatic toxicity. The identification of safer alternatives has been stymied by tradeoffs between safety and efficacy. To enable the identification of safer preservatives, substances from eight functional classes were assessed with respect to antimicrobial efficacy and human and environmental hazards. First, 130 substances were evaluated for microbial inhibitory activity against two relevant microorganisms, Aspergillus brasiliensis (filamentous fungi) and Pseudomonas aeruginosa (Gram-negative bacteria). High-performing compounds within each class were assessed for hazard across a broad suite of human and environmental health endpoints. Four promising compounds were selected for further testing based on microbial inhibition, hazard profiles, and cost and availability. These ingredients were tested for microbiocidal activity in model home care formulations using methods adapted from industrial preservative challenge guidelines. Two substances are identified – caprylhydroxamic acid and caprylyl glycol – that provide adequate preservation and improved toxicity profiles compared to existing isothiazolinone and formaldehyde-releasing preservatives. This study highlights tradeoffs between antimicrobial activity and human/environmental toxicity across a broad spectrum of chemical classes and provides insights into promising directions for further preservative development.