I shot heroin for a number of years, and many many times I would either be in a hurry or just lazy and would shoot up without using a cotton. Even with a cotton, there’s a lot of particulate matter that enters the syringe when you draw. I don’t use heroin now, but I often wonder what the ramifications are of all that matter entering my veins and if it bonded with any plaque from fat in my arteries and if this increases my risk of a heart attack in the future. I know of no studies into this and would like to see something come out and hopefully be able to assuage any worries of mine.