Statistical analyses
2.3.1. Descriptive analyses
All statistical analyses were performed in SAS (SAS version 9.2; SAS institute, Cary NC). We calculated descriptive statistics for each metabolite including the geometric mean concentration and selected percentiles (10th, 25th, 50th, 75th and 90th percentiles). We also examined the distribution of urinary BDCPP and DPP graphically. Urinary metabolite levels were skewed right. Accordingly, all quantitative analyses were conducted with natural log-transformed urinary BDCPP and DPP measures. We assessed the relationship between urinary BDCPP and DPP concentrations by calculating spearman correlation coefficients.