More research about the effects of secondhand marijuana smoke is still needed. The known risks of secondhand exposure to tobacco smoke—including risks to the heart or lungs—raise questions about whether secondhand exposure to marijuana smoke causes similar health risks. Secondhand marijuana smoke contains many of the same toxic and cancer-causing chemicals found in tobacco smoke and contains some of those chemicals in higher amounts.
More research is needed to understand how secondhand marijuana exposure may affect children. Secondhand marijuana smoke contains tetrahydrocannabinol (THC), the chemical responsible for most of marijuana’s psychological effects (or the “high”). THC can be passed to infants and children through secondhand smoke, and people exposed to secondhand marijuana smoke can experience psychoactive effects, such as feeling high., Recent studies have found strong associations between reports of having someone in the home who uses marijuana (e.g., a parent, relative, or caretaker) and the child having detectable levels of THC.,
Children exposed to THC are potentially at risk for negative health effects. Other research shows that marijuana use during adolescence can impact the developing teenage brain and cause problems with attention, motivation, and memory, suggesting that secondhand smoke exposure could lead to similar negative health effects in children.
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Source: Can secondhand marijuana smoke affect nonsmokers?