title: Exposures to endocrine-disrupting chemicals and age of menarche in adolescent girls in NHANES (2003-2008).
abstract: BACKGROUND
  The observed age of menarche has fallen, which may have important adverse social and health consequences. Increased exposure to endocrine-disrupting compounds (EDCs) has been associated with adverse reproductive outcomes.
  
  
  OBJECTIVE
  Our objective was to assess the relationship between EDC exposure and the age of menarche in adolescent girls.
  
  
  METHODS
  We used data from female participants 12-16 years of age who had completed the reproductive health questionnaire and laboratory examination for the Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey (NHANES) for years 2003-2008 (2005-2008 for analyses of phthalates and parabens). Exposures were assessed based on creatinine-corrected natural log urine concentrations of selected environmental chemicals and metabolites found in at least 75% of samples in our study sample. We used Cox proportional hazards analysis in SAS 9.2 survey procedures to estimate associations after accounting for censored data among participants who had not reached menarche. We evaluated body mass index (BMI; kilograms per meter squared), family income-to-poverty ratio, race/ethnicity, mother's smoking status during pregnancy, and birth weight as potential confounders.
  
  
  RESULTS
  The weighted mean age of menarche was 12.0 years of age. Among 440 girls with both reproductive health and laboratory data, after accounting for BMI and race/ethnicity, we found that 2,5-dichlorophenol (2,5-DCP) and summed environmental phenols (2,5-DCP and 2,4-DCP) were inversely associated with age of menarche [hazard ratios of 1.10; 95% confidence interval (CI): 1.01, 1.19 and 1.09; 95% CI: 1.01, 1.19, respectively]. Other exposures (total parabens, bisphenol A, triclosan, benzophenone-3, total phthalates, and 2,4-DCP) were not significantly associated with age of menarche.
  
  
  CONCLUSIONS
  Our findings suggest an association between 2,5-DCP, a potential EDC, and earlier age of menarche in the general U.S. population.
authors.affiliation: National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia, USA. iyk7@cdc.gov
authors.forename: Danielle E
authors.initials: DE
authors.lastname: Buttke
authors.forename: Kanta
authors.initials: K
authors.lastname: Sircar
authors.forename: Colleen
authors.initials: C
authors.lastname: Martin
mesh_terms: D000293:Adolescent; D000367:Age Factors; D015415:Biomarkers / Q000652:urine; D002648:Child; D002733:Chlorophenols / Q000652:urine*; D002851:Chromatography, High Pressure Liquid; D052244:Endocrine Disruptors / Q000652:urine*; D004781:Environmental Exposure; D004785:Environmental Pollutants / Q000652:urine*; D005260:Female; D006801:Humans; D008572:Menarche; D009749:Nutrition Surveys; D012959:Socioeconomic Factors; D053719:Tandem Mass Spectrometry; D014481:United States
chemical_list: D015415:Biomarkers; D002733:Chlorophenols; D052244:Endocrine Disruptors; D004785:Environmental Pollutants; C056892:2,5-dichlorophenol; C004762:2,4-dichlorophenol