Fig. 1From: The contribution of secondhand tobacco smoke to blood lead levels in US children and adolescents: a cross-sectional analysis of NHANES 2015–2018Log-scale scatter plot of serum cotinine and blood lead levels as continuous variables for all subjects (beta coefficient = 0.05, R-square = 0.11, p < 0.05). The bold line indicates a regression line, and the gray shade represents 95% confidence intervalsBack to article page