MIKE TAIBBI:

He is also concerned about marijuana-impaired driving.

For example, in Washington state, in its first year of legal marijuana sales, the percentage of drivers involved in fatal crashes who had marijuana in their system more than doubled from 8 percent in 2013 to 17 percent in 2014, that according to triple-A and the state's traffic safety commission.

But researchers are hesitant to draw any conclusions, because there's no clear method for collecting this data and no reliable test for when drivers become impaired from using marijuana. Marijuana can stay in your bloodstream for weeks.

Los Angeles police officer Kamaron Sardar says police are still searching for a tool like a breathalyzer to measure marijuana use and impairment. The LAPD is testing this oral fluid device.