When California’s regulators scrambled to make rules for the state’s new legal market, one issue was near the top of their list: How to deal with pot’s pesticide problem.

For years, pesticides used on black market and medical marijuana have affected water, wildlife, and consumer health. But until recently, the state had no way to prevent farmers from treating their crops with dangerous pesticides, fungicides or rodent killers. That’s all supposed to change with weed going legal, but growers, regulators and scientists say guaranteeing clean cannabis will be an uphill battle.

After a phase-in period of six months, which kicked off this week, any weed sold on California’s legal market has to test clean for residues of 66 pesticides — listed by the new Bureau of Cannabis Control. Growers say they’re already being tested at such minute levels that even weed grown organically could fail these tests. One problem is pesticides that drift from farms, which don’t have to comply with the same strict rules.

“Other crops can use fungicides and pesticides. For weed, nothing is allowed because cannabis is still illegal under federal law,” Shawn Webber, a licensed grower in Sonoma County, told VICE News.

Scientists say regulators have forgotten to extend their strict standards to the labs themselves. “It’s zero tolerance for pesticides, but at what level,” said Reggie Gaudino, Chief Science Officer at Steep Hill Labs, which offers cannabis testing in Berkeley, CA. “The regulations have no minimum standards for the machines that test the weed. People are going to shop around for the worst lab so they don’t fail.” And, as there aren’t enough labs to go around, product will spoil while it waits to be tested.

Growers who fail the tests or don’t want to invest in meeting the state’s rigorous standards, will likely return to black market. In other words, despite regulators’ best intentions, tainted weed won’t be off the menu just yet.

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