Recent testing and studies have showed that the drug can often contain pesticides as well as pathogens, including mold, mildew, E. coli and Salmonella. A study published in the Journal of Toxicology revealed that as much as 70 percent of the pesticides present in marijuana may be inhaled when the drug is smoked. These hazards are in addition to historically high THC levels and lower than normal levels of cannabidol, the chemical thought to give marijuana therapeutic properties.
While marijuana has become legal in several places, legislation regulating its production and safety is still catching up to legalization movements. And because it is still illegal at the federal level, the EPA has not created any regulations relating to which chemicals may be used to grow marijuana or their proper storage and usage. Using more concentrated forms of marijuana, such as hash oil also concentrates any pesticides in them, making the contaminants, often banned for human consumption by the EPA, that much more potent.