A California panel voted Wednesday to declare marijuana smoke and the drug's high-producing chemical -- THC -- a risk to pregnant women and their developing fetuses and require warning labels for products legally sold in the nation's largest pot market.

The decision by the little-known Developmental and Reproductive Toxicant Identification Committee will not take effect for a year, and it remains to be seen what impact it will have on the state's emerging marijuana industry.

The vote came after hours of discussion by a nine-member panel of scientists who delved into the reliability and accuracy of dense research studies involving people and animals, including mice, rats and fish.

Surveys have indicated that a rising number of mothers-to-be have turned to marijuana products for relief from morning sickness and headaches, though it's effectiveness has not been backed by science.

Since 2009, California has listed marijuana smoke as being known to cause cancer, similar to tobacco smoke. The vote adds THC and pot smoke to the list of chemicals the state has judged to be known to cause birth defects or other developmental problems and must carry warning labels.

Cannabis industry officials say too little sound research is available to support such a move and warn that it could make marijuana companies a target for lawsuits with unverified claims of injuries from pot use during pregnancy.

Ellen Komp, deputy director of the legal pot advocacy group California NORML, told the panel that the studies only examined women who smoked marijuana, not those who used vapes, topical lotions or other methods. Taken together, the studies "produced conflicting results," she said.

Some studies didn't make clear how frequently a mother used cannabis during pregnancy or what products were being used. Others didn't account for instances when mothers were using marijuana and tobacco and whether that could skew the results. In other cases, studies relied on self-reporting by new mothers, putting the reliability of the information in doubt.

The panel spent several hours debating the studies, and in the end, it found the weight of the evidence was sufficient.

The review was carried out under the umbrella of the Safe Drinking Water and Toxic Enforcement Act, better known as Proposition 65. It requires warning labels for chemicals judged as dangerous and allows residents, advocacy groups and attorneys to sue on behalf of the state and collect a portion of civil penalties for failure to provide warnings.

The 1986 law has been credited with weeding out cancer-causing chemicals from products but also faulted for setting the stage for legal shakedowns.

Lawyers looking for a quick buck will say "give us $10,000 or we are going to take you into a long court case," said Los Angeles dispensary owner Jerred Kiloh, who heads the United Cannabis Business Association, an industry group.

The California Cannabis Industry Association echoed that fear, noting that pot's standing as an illegal drug at the federal level has choked off research by government agencies.

"Good policy and consumer protections are based on facts and data," spokesman Josh Drayton said.

The U.S. surgeon general warned in August that smoking marijuana is dangerous for pregnant women and their developing babies. Mainstream medicine advises against pot use in pregnancy because of studies suggesting it might cause premature birth, low birth weight or other health problems, but many of those studies were in animals or had findings that were open to dispute.

The National Institute on Drug Abuse is paying for several studies on marijuana use during pregnancy.

The California panel's decision raises questions about the impact on the state's legal pot industry.

During the one-year grace period, state officials will determine a level of exposure that does not present significant health risk and require warnings.

Presumably, packaging would need to be changed over time to carry warning labels for pregnant women. But such requirements would likely take additional steps by agencies that oversee marijuana regulation and packaging.

State law already requires pot packaging to carry a warning that marijuana use during pregnancy or breast feeding "may be harmful."

Even products containing CBD, a trendy ingredient extracted from marijuana or hemp, can contain trace amounts of THC.