Parabens are recognized as emerging contaminants. Used in the pharmaceutical and cosmetic industries, they present significant ecological risks to aquatic ecosystems. This study evaluated the effects of two parabens—methyl 4-hydroxybenzoate (methylparaben) and propyl 4-hydroxybenzoate (propylparaben)—both individually and as a mixture on daphnids. Through a series of controlled exposure experiments, phenotypic endpoints, including mortality, feeding behaviour, and enzymatic activity, were measured. The results demonstrate that propyl paraben and the mixture of propyl and methyl paraben exhibit greater toxic potential compared to methyl paraben alone. We observed a dose-dependent impact on key enzymes, indicating significant metabolic disruption. These findings underscore the necessity of utilizing model systems to investigate the complex interactions and cumulative impacts of pollutant mixtures in aquatic environments. Furthermore, this study provides critical insights regarding the underlying toxicity mechanisms of parabens, highlighting the need for comprehensive water quality monitoring and risk assessment frameworks to address the challenges posed by emerging contaminants.

Humanity faces the great challenges arising from pollution and climate change which evidently lead to the irreversible effects observed on the planet. It is now more important than ever to monitor and safeguard the ecosystem as it has been highlighted by governments and scientists. Conventional approaches for water pollution rely on the detection of chemicals in the environment. However, these descriptive observations when compared against water quality standards used as metrics for pollution are unable to predict pollution early or capture the extent of its impact. This weakness is reflected in the legislation and the thresholds for emerging pollutants such as pharmaceuticals and nanomaterials. To bridge the gap and to understand the underlying mechanisms for toxicity, research in the field of molecular ecotoxicology shifts more and more towards the integration of model systems, in silico approaches and molecular information as endpoints. Focusing on the freshwater ecosystem, daphnids are key species employed in risk assessment which are characterised as highly responsive to pollutants and physical stressors. The translation of molecular information describing the physiology of these organisms provides novel and sensitive metrics for pollution assessment.