Fig. 3: Trans-3’-hydroxycotinine multivariable linear regression model.

Standard regression coefficients (point) and their 95% confidence intervals (line) are displayed for each variable in a model predicting log-transformed urinary trans-3’-hydroxycotinine concentration. Variables related to secondhand smoke are shown in red, variables not related to smoking in blue, and variables related to household characteristics in gray. Note that the ingestion of breast milk is an indirect source of nicotine from secondhand or thirdhand smoke, or dietary nicotine sources. Intervals with a point estimate of the regression coefficients that are displayed as a circle are based on bivariate analysis between each predictor and urinary trans-3’-hydroxycotinine concentration while estimates displayed with a triangle reflect estimates from a multivariable model.