Association between nonylphenol exposure and development of secondary sexual characteristics

Previous studies have reported that p-nonylphenol (NP) can advance the age at vaginal opening in prepubertal rats. A significant exposure levels of NP was found in Taiwanese population even from the prenatal stage. The purposes of this study are to examine the urinary NP concentration of pubertal students in Taiwan and to explore its association with the development of secondary sexual characteristics. 786 pubertal students were recruited. The NP was determined using solid-phase extraction and high-performance liquid chromatography with fluorescent detection. A self-administered questionnaire was used to collect the data on occurrence of secondary sexual characteristics in the subjects. About 30% of the urine samples were positively detected. The NP concentrations ranged from ND to 178.25 μg g-1 cr. Fifteen percent of the Taiwanese girls between 10.5 and 10.9 years old reported having undergone menarche, which was higher than the white girls (4.6%) and the black girls (8%). There was no significant difference of urinary NP levels between groups of having and not having secondary sexual characteristics because body mass index (BMI) had significant effects on sexual development. After adjusting the effect of age and BMI, the menarcheal age remained inversely correlated with the increase of urinary NP levels. Nonylphenol exposure could disturb pubertal development and the pubertal girls seem more sensitive than pubertal boys to the exposure of endocrine disruption chemicals (EDCs). The effects of early maturation as well as the health implications need further study.