WHY IT MATTERS: If you or someone in your household has asthma or another respiratory condition, exposure to secondhand marijuana smoke in shared spaces like homes or vehicles can trigger serious symptoms even without directly using cannabis. CLINICAL OVERVIEW: Secondhand marijuana smoke contains fine particulate matter that can trigger respiratory inflammation and exacerbate conditions like asthma, making exposure a legitimate public health concern beyond the individual user. Unlike the common assumption that cannabis smoke is less harmful than tobacco smoke, the combustion process produces many of the same irritants and carcinogens regardless of the plant material being burned.