Objectives: Animal studies had revealed that young mice exposed to p-nonylphenol (NP), a kind of alkyphenols, might develop motor hyperactivity at adolescence, probably by inhibiting the growth of dopaminergic neurons. This study aimed at clarifying the association between p-nonylphenol (NP) exposure and the clinical symptoms of attention-deficit hyperactivity disorder (ADHD) in children.

Methods: From July, 2012 to June, 2013, all children newly diagnosed as ADHD in Taipei City Hospital, Zhong-Xiao branch and Yang-Ming branch, were invited to join this study. The diagnosis of ADHD was  based on the criteria of DSM-IV-TR. The severity of clinical symptoms of ADHD was quantified by SNAP-IV rating scales, including parent-rating and teacher-rating versions. Blood lead level and urinary NP concentration were analyzed for each participant.

Results: In total, 35 children with ADHD and 33 normal children as control subjects were enrolled in this study. The average blood lead levels in both groups were similar (1.4±0.6 v.s 1.3±0.6μg/dL, p=0.49). However, children with ADHD had significantly higher urinary NP concentration than normal controls (5.0±2.3 v.s 3.7±2.2 ppb, p=0.02). Although there was no significant correlation found between urinary NP concentration and total SNAP-IV rating scales, a trend association still could be observed between urinary NP levels and hyperactivity/impulsivity scores in teacher-rating SNAP-IV scales (Spearman r=0.29, p=0.09, n=21)

Conclusions: Significantly elevated urinary NP levels were found in children with ADHD and probably associated with more severe hyperactivity/impulsivity symptoms. These results implied that exposure to NP may be associated with ADHD, especially hyperactivity/impulsivity symptoms.