Denver - Marijuana may be coming out of the black market in Colorado and Washington state, but the drug, at least for now, will retain a decidedly underground feel: Users may not know what's in it.

Less than a year away from allowing pot sales, regulators are grappling with how to ensure that the nation's first legal marijuana industry will grow weed that delivers only the effects that pot smokers want.

Whether it is establishing rules to govern the growing of marijuana, including the use of pesticides and fungicides, or accurate product labeling, officials know they will be doing it alone.

Federal agencies that regulate food and drugs are staying out because pot remains illegal under federal law. That means the states are starting from scratch to protect consumers from pot that could be tainted by mold, mildew or unwanted chemicals.

Whatever regulatory scheme officials in the states choose, there is little reliable product history to even know where to begin identifying marijuana safety risks, said David Acheson, a food safety consultant.

When it was illegal, few users could come into the health department to complain that a stash of weed they bought was bad, said Acheson, a former assistant commissioner for the Food and Drug Administration.

"As it becomes legal, we could see many problems emerge. We just don't know," he said.

Medical marijuana product safety has long been a concern in Colorado. Critics say the regulations were too loosely lax, and that any new regulations for pot should be stringent, and rigorously enforced.

Colorado has one operational product testing facility for marijuana potency and content. Product testing is voluntary and paid for by interested pot consumers and sellers, not state regulators.

"I've seen stuff in grow houses - oh my God, you don't even want to know about," said Genifer Murray, the owner of CannLabs, a Denver lab that tests marijuana. She said she has seen cans of bug spray next to marijuana, plants covered with powdery mildew and lax sanitation.

"There's no other plant like this that you smoke and eat and use as medicine," Murray said. "Everybody's entitled to a safe and effective product, and right now it's completely hit and miss. What exactly are you buying?"

Colorado requires labels on edible pot, including an ingredient list and recommended expiration date. Potency and dosing, though, are left to the buyer to figure out. Labels read, "Levels of active components of medical marijuana reported on product labels are not subject to independent verification and may differ from actual levels."

The state has detailed production safety guidelines and a three-page list of pesticides and other chemicals that can't be used on marijuana, including arsenic and mercury. But in Colorado's three-year history regulating medical-marijuana production, the state has levied no enforcement actions for a safety or sanitary violation.

Colorado and Washington officials are considering going further when it comes to marijuana for sale to all adults, though neither has decided what to do. The states will first have to decide whether to treat marijuana like something that is smoked or something that is eaten.

Colorado copies tobacco pesticide regulations to apply to medical marijuana. But regulators rejected a proposal to certify "organic" pot grown without any pesticides, leaving consumers with no way to verify organic processing claims.