As you said, atherosclerosis is a pathology in which our capillary vessels are affected by different external factors that generate a constriction in many arteries so it's become difficult for our body to correctly drive blood along all our organs.
The constant exposure to toxic gases, like one's presents in the smoking process, (e.g. carbon monoxide (CO), and polycyclic hydrocarbons) causes an accumulation of material within the arteries, (that settles or sediment themselves on the inner walls of these capillary vessels) composed mainly of fats and cholesterol, which inhibiting a good blood flow.