The 4/20 marijuana holiday, which drew thousands to a smoke-filled public party in San Francisco, ignited in California as pot advocates ramp up a major legalization campaign amid a renewed debate on the mental health risks of heavy cannabis use.

The unofficial National Weed Day lit up Hippie Hill in Golden Gate Park with raucous and colorful pot-themed festivities on Wednesday in what is probably the final 4/20 event before recreational cannabis becomes a reality in California.

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Establishing strict regulations before the retail industry booms is critical for public health and safety, said Michelle Mello, Stanford professor of law and of health research and policy, who has written about the dangers of legal edibles.

“These issues have to be thought through before legalization comes online … when you still have a little bit of leverage as a regulator and are not going to be held hostage to a powerful lobby,” she said.