But large cannabis producers are now pushing to clamp down on Delta-8 THC amid worries that a lack of oversight means heavy metals and unexpected intoxicants are cropping up in some of the products.

The cannabis compound has proliferated in gummies, joints and vape pens, with sales more than doubling in the past year across the country. Despite being almost chemically identical to federally outlawed forms of marijuana, Delta-8 has escaped widespread scrutiny thanks to ambiguity in U.S. laws.

That's starting to change, with a coalition of cannabis producers now pushing federal and state regulators to block sales of unregulated Delta-8. More than a dozen states have already moved to restrict the products.

The previously unreported effort by industry leaders to rein in the booming but unchecked sector comes as chemists and health advocates sound alarms over potentially dangerous contaminants, such as lead and arsenic, and unpredictable potency levels in some commercially available products. Two tests of Delta-8 samples — one by the U.S. Cannabis Council trade group and another commissioned by Bloomberg News — found high levels of intoxicants in several of the products, as well as metals in some of them.

Delta-8 is particularly concerning to some scientists because it can be easy to make. Users can simply mix over-the-counter CBD with battery acid, pool chemicals or even household vinegar to produce it, although there are methods that don't use acids.