Comparison of the baseline and follow-up urine mercury measures for treatment and positive amalgam groups. Box and whisker plots showing distributions of urine mercury concentrations for each group (μg/g-creatinine). Corresponding numeric data are provided in Table 3. Boxes extend from the 25th to the 75th percentile, horizontal bars inside the boxes represent the median, whiskers extend to maximum and minimum observations within 1.5 times the length of the interquartile range above and below the 75th and 25th percentiles, respectively, and outliers are represented as circles. Group comparison was performed using the Kruskal-Wallis with Dunn’s multiple-comparison test p < 0.05. A Wilcoxon signed-rank test was used for inter-group comparison and all were statistically significant (p < 0.001). Lower case letters indicates distributions that are not significantly different. Values >10 μg/g-creatinine have been removed for readability. * signifies an extreme outlier: one at 12 μg/g-creatinine in the positive group and two at 11 and 23 μg/g-creatinine in the never amalgam group.