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Though very uncommon, one of the dangers of smoking marijuana is the possibility that it has been laced with another, more dangerous substance such as cocaine, crack, meth, PCP, or even embalming fluid(formaldehyde). Dealers have been known to sell joints, blunts, or cigarettes dipped in embalming fluid and laced with PCP. Though reports of laced marijuana are infrequent, and most lacing of marijuana is done at user-level, it is important to remember that with unregulated drugs such as marijuana, the user has no way of knowing what other types of substances have been added.
99.9% dealers you will see are out to make a profit in selling 'drugs'. You will notice the more drugs you buy the more money it costs right? Well yes of course, so why would such a dealer lace some cheap cannabis (for example, 2g of middies for $10) that was only $10 worths with something as 'Cocaine' that can be up to averaged price of $65?! Now that doesn't make sense does it? So again, in shorter terms.. 99.9% dealers don't waste $55 in profit JUST to lace your bud.
Alright, now that we got done with the theory of lacing bud which is majority of our blades problems and usually the issues turns out that it isn't even laced! But if perhaps you still think so we will go through in a inspection to see if our bud is laced.
First thing you want to do is smell the bud, does it smell more distinct then normal or does it smell the same, *Take in mind that different cannabis strains of course have different smells*.
If it doesn't smell like any kind of bud what so ever and smell's more 'chemically' then let's move on to looking closer on the buds. Usually 3/4 of the time, visually you wouldn't be able to tell if it was laced. But for this part just look at it to see if it appears as normal, you don't want to be seeing things such as, crazy madness of snowy buds that falls usually when shaked and if the color seems as normal as what you usually buy.
When individual users lace marijuana, they may sprinkle powdered cocaine or crack into a joint or blunt, combining the stimulant effects of cocaine with the depressant and hallucinogenic effects of cannabis. This can be very dangerous, especially for a person with not tolerance to cocaine. Users have also been known to snowcap bowlfuls of marijuana with powdered opium or heroin, in addition to cocaine and crack. Again, combining other drugs with marijuana can be extremely dangerous. You have a greater chance of getting laced weed, if you buy pre-rolled joints or blunts..there's no way for you to see if there is a powdery substance inside.
Smoking a joint that has been dipped in embalming fluid or formaldehyde has effects similar to those of a joint laced with PCP - a drug that causes hallucinations, euphoria, and often times, panic or rage. Having a negative reaction is even more likely if the user is expecting only the normal marijuana high. In addition to these psychological dangers, marijuana that has been laced is also extremely unhealthy. Formaldehyde is a known carcinogen linked to nasal and lung cancer, with possible links to brain cancer and leukemia, and should not be smoked or ingested in any way. Laced marijuana is also refered to as "Wet Weed"
Part of this article taken from http://www.cesar.umd.edu/cesar/drugs/marijuana.asp
in the last month, there has been 3 deaths of teenagers who smoked weed that was coated in a fine powdered glass.... 
