[muwtyhg]

Not all marijuana vaping is done using vape pens containing Propylene Glycol. You can vaporize concentrate, which doesn't include any sort of additive and is tested for pesticides and heavy metals in places like California. PG just helps the concentrate "flow" into the wick of the vape pen. You also don't need to use a vape pen where the heating element is exposed to the airflow of the concentrate, reducing the chance of heavy metals being released.

There are also vaporizers that just pass hot air over marijuana flower.