Surfactants in Personal Care Products: Detrimental Effects of Sodium Lauryl Sulfate on Freshwater Fish and Amphibians Embryos

In Personal Care Products (PCPs), sodium lauryl sulfate (SLS) is one of the main surfactants used in their formulation as an emulsifying cleaning agent. Introduced in the second half of the 20th century, SLS increased its presence in PCPs after the COVID-19 pandemic with a demand of over $28.8 billion in 2023. The rising demand caused an increase in the accumulation of SLS in the aquatic environment leading it to be regarded as a pseudo-persistent agent with an amount detected in freshwater bodies between 1.15 and 24 mg/L that may cause adverse effects on the communities. Even though the SLS-based products of daily personal use (such as toothpaste, cosmetics, shampoos, detergents, and many others) are still frequently used, most studies on the risk to ecosystems and non-target species were conducted before 2010. Therefore, the present study aimed to investigate the effects of SLS on three freshwater vertebrates. Applying embryotoxicity tests to the embryos of two fish (Cyprinus carpio, Danio rerio) and one amphibian species (Xenopus laevis), the possible harm caused by SLS exposure and the differences in action on different model organisms were evaluated. Embryos were exposed to six concentrations of SLS (0.1, 0.5, 1, 5, 10, and 15 mg/L) and one control group for 96h. During the experimental phase, the embryotoxicity endpoints of mortality, hatching rate, and occurrence of malformations were monitored every 24h. Additionally, the heartbeat rate alteration was evaluated after 48h of exposure for the fish organisms and after 52h for the frogs due to the transparency of the eggs. The results obtained from the analyses highlight a high sensitivity of D. rerio and X. laevis when exposed to environmental concentrations of SLS. Specifically, the results showed significant mortality of these two species in higher concentrations, alteration in hatching rate, and presence of many malformations on the body of the animals. Such effects were, however, not detected, in C. carpio embryos. In contrast, the results obtained for the heartbeat rate analyses showed significant differences in C. carpio and D. rerio embryos compared to the control. Such changes were not observed in X. laevis embryos. Such outcomes draw attention to the importance of conducting ecotoxicological analyses on multiple model organisms better to understand the real effects on the aquatic environment. Continued investigation will allow for a more comprehensive understanding of SLS’s mechanisms of action and its interaction with biological systems, ultimately informing the development of safer formulations and mitigation techniques.