Health - Different Drug Toxicity Levels?

[TripsBalls]

Swim is interested in figuring out the toxicity levels of different drugs.
ie. how harmful some drugs are in comparison to others.

Swim would like to know which drugs pose the most threat to Swims health.

Swim only takes certain drugs on a regular basis these days and he would like to know which of those is more toxic in relative to each other.

The drugs are: Heroin, Alcohol and Tobbaco.

Swim only uses these once or twice a week, he finds that the alcohol and tobbaco is more negative on his body than heroin.

Any opinions, or info on drug toxicity would be much appreciated.