Environmental occurrence, ecological risks, and microbial interactions of p-chloro-m-xylenol: An emerging ubiquitous antimicrobial agent

Abstract

p-Chloro-m-xylenol (PCMX), a halogenated phenolic antimicrobial agent, has gained global prominence in disinfectants and personal care products. This review synthesizes current knowledge on PCMX's environmental occurrence, ecological impacts, and microbial transformation mechanisms. Environmental monitoring reveals pervasive contamination (ng/L to mg/L) across wastewater systems and surface waters, with seasonal and regional variability linked to consumption patterns and treatment inefficiencies. Ecotoxicological assessments demonstrate acute toxicity to aquatic organisms and chronic effects, such as developmental abnormalities, endocrine disruption, and neurobehavioral impairments. Emerging evidence highlights PCMX's role in promoting antibiotic resistance gene dissemination via enhanced horizontal gene transfer. Critically, microbial degradation studies identify Rhodococcus species as key degraders, employing pathways involving dechlorination to 2,6-dimethylhydroquinone or hydroxylation to 4-chloro-3,5-dimethylcatechol. Mechanistic insights reveal a flavin-dependent monooxygenase (CxyA) catalyzing initial transformation, though genetic regulation and roles of associated enzymes (e.g., CYP450) require further elucidation. This review establishes PCMX as a nonnegligible emerging contaminant, emphasizing the need for coordinated monitoring strategies, refined ecological risk assessment frameworks, and innovative bioremediation approaches to mitigate its environmental impacts.