There is potential for increased sinus infections, bronchitis, and it aggravates allergies. This is also taken from the Mayo Clinic website:
How risky is secondhand smoke?
Secondhand smoke causes or contributes to serious health problems, including:
Lung disease. Exposure to secondhand smoke can aggravate respiratory conditions — especially for people who have asthma or chronic obstructive pulmonary disease (COPD).
Heart disease. Secondhand smoke damages blood vessels and interferes with circulation, which increases the risk of heart disease and heart attack. A new Mayo Clinic study suggests that secondhand smoke also increases the risk of sudden cardiac death.
Cancer. Secondhand smoke is a known risk factor for lung cancer. In addition, secondhand smoke contains benzene — which increases the risk of leukemia.