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Urinary trichlorophenol levels and increased risk of attention deficit hyperactivity disorder among US school-aged children
  1. Xiaohui Xu1,
  2. Wendy N Nembhard2,
  3. Haidong Kan3,
  4. Greg Kearney4,
  5. Zhi-Jiang Zhang5,
  6. Evelyn O Talbott6
  1. 1Department of Epidemiology and Biostatistics, College of Public Health and Health Professions, University of Florida, Gainesville, Florida, USA
  2. 2Department of Epidemiology and Biostatistics, College of Public Health, University of South Florida, Tampa, Florida, USA
  3. 3Department of Environmental Health, School of Public Health, Fudan University, Shanghai, China
  4. 4National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
  5. 5Department of Epidemiology, School of Public Health, Shanghai Jiao Tong University, Shanghai, China
  6. 6Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, USA
  1. Correspondence to Xiaohui Xu, 101 S Newell Drive, Room 3119, Gainesville, FL 32610-0182, USA; xhxu{at}


Background Trichlorophenols (TCPs) are organochlorine compounds which are ubiquitous in the environment and well known for their carcinogenic effects. However, little is known about their neurotoxicity in humans.

Objectives Our goal was to examine the association between body burden of TCPs (ie, 2,4,5-TCP and 2,4,6-TCP) and attention deficit hyperactivity disorder (ADHD).

Methods We calculated ORs and 95% CIs from logistic regression analyses using data from the 1999–2004 National Health and Nutrition Examination Survey (NHANES) to evaluate the association between urinary TCPs and parent-reported ADHD among 2546 children aged 6–15 years.

Results Children with low levels (<3.58 μg/g) and high levels (≥3.58 μg/g) of urinary 2,4,6-TCP had a higher risk of parent-reported ADHD compared to children with levels below the limit of detection (OR 1.54, 95% CI 0.97 to 2.43 and OR 1.77, 95% CI 1.18 to 2.66, respectively; p for trend=0.006) after adjusting for covariates. No association was found between urinary 2,4,5-TCP and parent-reported ADHD.

Conclusion Exposure to TCP may increase the risk of behavioural impairment in children. The potential neurotoxicity of these chemicals should be considered in public health efforts to reduce environmental exposures/contamination, especially in countries where organochlorine pesticides are still commonly used.

  • 2,4,6-Trichlorophenol, organochlorine chemicals
  • Neurotoxicity, attention deficit hyperactivity disorder, pesticide
  • epidemiology
  • paediatrics

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  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the University of Florida IRB.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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