The issue is, despite marijuana being legal in over 20 states, only a handful have implemented measures to ensure product quality.

For instance, in California, laboratory testing is completely optional. And that's bad news, warns Jeffrey Raber, who holds a Ph.D in chemistry and runs a marijuana testing lab called The Werc Shop.

According to Dr. Raber, pesticides are present in about 10% of samples that are sent to The Werc Shop. While mandatory lab testing would be the ideal solution, Dr. Raber recently set out to determine just how much risk pesticides really pose.

His study, published in the Journal of Toxicology, shows that using a filtered smoking device can drastically reduce the conversion of pesticides into inhalable smoke.

Dr. Raber and his team used a McFinn's Triple Filtered Water Pipe for the study, which filters smoke through both cotton and carbon layers.

Unfiltered pipes and bongs, however, appear to offer far less protection against pesticides.

While research has yet to identify the specific health effects of smoking contaminated marijuana, Dr. Raber believes that patients with compromised immune systems are most at risk. 

Source: Times-Standard via LeafScience