There are two primary sources of damage from inhaled tobacco smoke. The smoke itself is made up of polycyclic aromatic hydrocarbons like anthracene. These mole

There are two primary sources of damage from inhaled tobacco smoke. The smoke itself is made up of polycyclic aromatic hydrocarbons like anthracene. These molecules are carcinogenic on their own, and activate the bodies' inflammation response causing additional damage. In this regard, both marijuana and tobacco will have very similar detrimental effects. However, some of the compounds found in marijuana, like cannabidiol, are anti-inflammatory agents (targeting the CB2 receptor), which helps prevent some of the damage that would otherwise be caused by the smoke (but not all of it). The other source of damage is radioisotopes absorbed from the soil. The tobacco plant tends to absorb radioactive elements like polonium more readily than many other plants. These radioisotopes are deposited on the lining of the lungs, where they undergo decay, causing cellular damage. Marijuana may or may not be similar to tobacco in this respect, but I have not done much research on that.