It can be hard to keep legal marijuana out of the hands -- and mouths -- of small children as the U.S. becomes increasingly pot friendly, especially when some products look like the kinds of snacks and treats kids crave. As marijuana edibles – foods infused with cannabis for a high-inducing kick – become more popular among adult marijuana consumers, more children are getting exposed to the drug. From 2006 to 2013, children’s exposure to marijuana products rose 147.5 percent across the U.S., according to a study published Monday in the journal Clinical Pediatrics. In states with legal medical marijuana, that figured jumped to 610 percent.

Most children were exposed after swallowing marijuana edibles. "The high percentage of ingestions may be related to the popularity of marijuana brownies, cookies and other foods," Henry Spiller, a co-author of the study and director of the Central Ohio Poison Center at Nationwide Children's Hospital in Columbus, Ohio, said in a statement. "Very young children explore their environments by putting items in their mouths, and foods such as brownies and cookies are attractive." The majority of children – 75 percent – who ingested pot were under 3 years of age, according to the report.

Some 1,969 children under the age of 6 were reported to U.S. poison control centers for marijuana exposure between 2000 and 2013, according to researchers. In Colorado and Washington, the first states to legalize recreational marijuana, marijuana-related calls to such centers spiked in the years following legalization in 2012, according to a recent report from the Associated Press. The Washington Poison Center received 246 calls in 2014 involving children exposed to marijuana, up from 158 a year earlier.

Researchers found that most of the exposure led to only minor adverse health effects. However, some children suffered more serious consequences, such as decreased breathing, seizures and even comas. Eighteen percent of children exposed to marijuana between 2000 and 2013 were hospitalized.

Twenty-three states and the District of Columbia have legalized medical marijuana. Four states and D.C. allow marijuana use for any purpose for adults 21 and older.

Public health officials have raised concerns that the new availability of marijuana could make it easier for children to come into contact with pot products. The Colorado Department of Public Health and Environment pushed for a ban on edibles last year that would have pulled cannabis-infused foods from store shelves. However, the state has not moved toward such a restriction.