Brominated phenols as emerging environmental contaminants: a review on environmental occurrence, toxicity, transformation and remediation strategies

Brominated aromatic compounds, specifically bromophenols (BPs), occur naturally in marine environments and are extensively used in different industrial processes such as the synthesis of brominated flame retardants (BFRs), pesticides, wood preservatives, and other consumer products. Their extensive demand, usage, and continuous release into the environment have led to their prevalence in water, air, sediments, biota, and humans raising significant ecological and public health risks. Several studies have shown that bromophenols exhibit genotoxic, phytotoxic, neurotoxic, endocrine-disrupting, and oxidative stress-inducing properties in humans, plants, aquatic organisms, and mammals. This review critically examines the available literature on the sources, environmental occurrence, toxicity, and treatment strategies of bromophenols, with a major focus on mono-, di-, and tri-brominated phenols. The review provides detailed information about the conventional and biological treatment strategies used for the removal of phenolic contaminants, their operating conditions, cost, and the formation and toxicity of transformation products. The literature indicates that traditional treatment options like advanced oxidation, electrochemical oxidation, adsorption, ozonation, and photocatalysis have shown considerable pollutant removal efficiencies but are cost-intensive and generate toxic by-products/metabolites. In contrast, bioremediation approaches using bacteria, fungi, and algae offer a promising sustainable alternative, however their efficiency is greatly influenced by different physico-chemical parameters which can limits its validation in real-world settings. Overall, the review highlights that pollutant removal alone does not imply the complete detoxification, it needs to be integrated with toxicity assessment of the metabolites/products formed and process optimization. Future research should combine convention treatment strategies with biological systems and advanced technologies such as omics and metabolic engineering for the efficient removal and detoxification of brominated phenols in contaminated environments.