what percentage of the world smokes cigarettes Visualizing Smoking Population Countries World's Highest Smoking Rates -

Both nicotine and smoke-related toxins, such as PAHs, have complex pharmacodynamic effects in cancer treatment, with interactions between apoptosis, tumour angiogenesis, host immune function and chemosensitivity [42]

27 LiY.YuanK.CaiC.FengD.YinJ.BiY.et al (2015)

When someone smokes a cigarette, most of the smoke doesnt go into their lungs

Just a guess for this female mannerism: insecure, afraid to lose that cigarette

What Are the Consequences of Illegal Vaping and Tampering with Fire Protection Equipment

While this doesnt mean fresh odours cannot attach, it does mean that existing smells are not worsening if fresh smoke is experienced