call poison control in your area..it should be in the front of your phone book
http://www.nlm.nih.gov/medlineplus/ency/article/002702.htm#Expectations%20(prognosis)
This link can give you some info... although it deals in specific poisoning due to accidental ingestion or deliberate suicidal intent.
http://www.hpa.org.uk/Chemicals/compendium/sodium%20hypochlorite/acute.htm
The second may be more appropriate to your needs. There are long term neuropsychological effects that can occur from ingesting bleach over time. Tell him there are better, safer ways to pass drug tests!!!
Oh no! That sounds very scary! I would just google it, I find my life on that website. I wish had more to tell you, but I don't, I actually haven't ever heard of that, I would have thought you would die from doing it, but I guess not. Well, well, I learn something new everyday:)
Good luck to you and your son.