Fig. 4

Shows the combined effect of exposure and 95% confidence intervals using the BKMR model. (A) In the 30–59 years old population, the increasing level of the metal mixture was significantly negatively associated with shortened rTL in the 55th to 75th range; (C) In the ≥ 60-year-old population, the increasing level of the metal mixture was linearly associated with longer rTL in the 25th to 70th range. Upward trends or positive percent change estimates indicate a positive correlation. Downward trends or negative percent change estimates indicate a negative correlation. In the separate effects model, the outcome variable changed with each interquartile spacing increase in individual metal concentrations when the metal concentration levels were at the 25th, 50th, and 75th percentiles, respectively. (B) 30-59years old; (D) ≥ 60 years old. The red line represents the 25th percentile, the green line represents the 50th percentile, and the blue line represents the 75th percentile.Models were adjusted for smoke, drink, sex, age, ethnic, education, overweight and fat.