Generally speaking "weed usage" introduces far fewer carcinogens compared to "cigarette usage" - but lots of things are bad for you including alcohol and, especially, sugar.
Not a carcinogen: sugar.
Sugar demonization is out of control. Many people eat an unhealthy amount of it, but any level of tobacco or alcohol consumption harms health.
And sugar needs to be vilified more if anything. I would bet healthcare spending on issues related to excess sugar/carbohydrate consumption (aka being overweight) dwarf anything else.
That's not because simple sugars are inherently bad for you but rather because many people don't realize just how much of it fruit juices contain. Related to this, an older family member was warned by a doctor for various reasons to cut back on fruit intake (not juice, but fruit itself).
So it's possible to consider it as even worse than some carcinogens.
I never buy juice unless it's roughly 80-100% plus in vitamin c and it contains 0 added sugars. I'm often shocked how many "juices" are literally de-carbonized soda with a healthy looking image.