Fig. 3.

Ratio of viral RNA in EBA with to without mask controlling for cough, age, sex, BMI, and SARS-CoV-2 variants. a) Fine aerosol, b) Coarse aerosol, c) Total aerosol. The solid diamonds denote the effect estimates, and the error bars show the 95% confidence interval of each estimate. We estimated the ratio of masked to unmasked EBA viral load by aerosol size using linear mixed effect models for censored responses (R package ‘lmec’, version 1.0²⁴), controlling for numbers of coughs during the 30-min sampling period, age, sex, BMI, SARS-CoV-2 variants, and random effects of participants and samples within the participant. In a post-hoc test, the difference between N95 and cloth mask in coarse EBA was confirmed to be statistically significant despite a slight overlap in confidence intervals in the lower panel.