Baseline characteristics of nonsmoker^* hospitality workers who completed follow-up at 12 months.

*Defined as workers who reported they were former or never smokers in the baseline and follow-up interviews, and had salivary cotinine concentrations <20 ng/ml. (Workers who changed smoking status between surveys were considered smokers and hence excluded from this analysis.) †p-values for comparison of medians (Wilcoxon's test for independent samples) and categorical variables (Fisher's exact test). ‡Any of the following: breathless while wheezing, woken up with a feeling of chest tightness, attack of shortness of breath at rest, woken by attack of shortness of breath, usually cough first thing in the morning in winter, usually cough during the day or night during winter, usually bring up phlegm during day or night in winter, had asthma attack. IQR: interquartile range