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Chloroxylenol (PCMX) at ≥0.4 mg/L induces ocular malformations and visual impairments, and at ≥1.2 mg/L disrupts circadian rhythms and sleep/wake behaviors in zebrafish larvae, with melatonin intervention alleviating sleep deficits.

Exposure to PCMX at concentrations ≥0.4 mg/L caused ocular malformations and suppressed photoreceptor development via disrupted thyroid hormone signaling in zebrafish larvae. At 2 and 2.8 mg/L, it impaired image-forming vision and visuomotor responses, while at ≥1.2 mg/L it disrupted circadian clock gene expression and induced daytime hyperactivity and insomnia-like sleep fragmentation, which were alleviated by melatonin treatment.

Last updated: Jul 15, 2026•0 RCTs•📖 Read as article →

Evidence Score

Evidence Score24/100
Human RCT☆☆☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. Chloroxylenol impairs the visual system, induces visually-mediated behavioral abnormalities and circadian rhythm disorders in zebrafish (Danio rerio).

observational

Man X, Bao Y, Feng X · Comparative biochemistry and physiology. Toxicology & pharmacology : CBP (2026)

Participants: N/A
Duration: Not specified in abstract
Intervention: PCMX exposure at 0.4, 1.2, 2, and 2.8 mg/L; melatonin intervention for sleep/wake deficits
Outcome: Ocular morphology, retinal development, visual-mediated behaviors (image-forming and non-image-forming vision), circadian rhythmic expression of melanopsin and core clock genes, sleep/wake behaviors
Effect Size: N/A
Population: Zebrafish (Danio rerio) larvae

Result:

PubMed: 42442645DOI: 10.1016/j.cbpc.2026.110616

Mechanism Graph

PCMX suppresses expression of key genes regulating photoreceptor proliferation and differentiation
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PCMX disrupts thyroid hormone signaling
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This inhibits photoreceptor development and causes retinal pathology
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Result: Impaired image-forming vision and visual-mediated behaviors; additionally, PCMX disrupts melanopsin gene rhythmicity and core clock gene expression, leading to circadian rhythm disorders and abnormal sleep/wake behaviors

Limitations

  • ⚠Study conducted in zebrafish larvae, limiting direct generalizability to humans or other mammals
  • ⚠No long-term exposure or recovery data provided; effects beyond larval stage not assessed

Frequently Asked Questions

What concentration of PCMX caused visual impairments in zebrafish?▼

Ocular malformations were observed at concentrations ≥0.4 mg/L, while impairments in image-forming vision and visuomotor responses occurred at 2 and 2.8 mg/L.

Did melatonin help with PCMX-induced sleep problems?▼

Yes, melatonin intervention effectively alleviated the sleep/wake behavioral deficits, including daytime hyperactivity and insomnia-like sleep fragmentation.

How does PCMX affect circadian rhythms?▼

At concentrations ≥1.2 mg/L, PCMX disrupted the rhythmic expression of core clock genes and melanopsin family genes in the non-image-forming visual system, leading to circadian rhythm disorders.

What is the ecological relevance of this study?▼

PCMX is frequently detected in aquatic environments, and this study shows it can impair vision, behavior, and circadian rhythms in zebrafish, indicating potential ecological risks to aquatic organisms.

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References

  1. 1.Man X, Bao Y, Feng X. "Chloroxylenol impairs the visual system, induces visually-mediated behavioral abnormalities and circadian rhythm disorders in zebrafish (Danio rerio).." Comparative biochemistry and physiology. Toxicology & pharmacology : CBP, 2026. PMID: 42442645 DOI: 10.1016/j.cbpc.2026.110616
Disclaimer: This content is for educational purposes only and is not medical advice. Evidence scores reflect the quality and quantity of available research, not clinical recommendations. Always consult a healthcare professional before starting any supplement or intervention.