Subject: How are free radicals produced?

 I recently read about free radicals in a 'special topics' article in my
chemistry textbok. I understand what they are (somewhat) and i also learned
that they are unhealthy to the body. I know they can affect the skin, cause
fats to oxidate, and do other undesirable things to our bodies.   Now my
question is, i'm not exactly sure how a free radical is produced but i'm
wondering if it could be formed from or there are some that exists in THC.
The intoxicating chemical in marijuana. I'll admit I have friends who do 
this
occasionally, and i've tried it once but I keep telling them it's not safe.
They have a whole argument from websites that says it is a weak drug without
permanent effects and there is no proof that it's harmful but I know it's 
not
something safe or a casual thing taken lightly. If their were free radicals
that exists in this chemical than it probably would cause harm to areas
around the brain that it's located in. Could you please enlighten me on the
subject. And maybe i can help some others too. Thanks

Re: How are free radicals produced?