Is your marijuana safe? Lack of data makes it hard to know in the long term

 Is your marijuana safe? Lack of data makes it hard to know in the long term

Regulators had to work with limited existing information on the possible risks of pesticides and contaminants in marijuana.

When Colorado and other states began legalizing marijuana more than a decade ago, they faced a problem: how to guarantee a safe product, with little data about the long-term risks of pesticides and o…