When the state’s new marijuana law goes into effect Thursday, anyone age 21 or older will be able to possess and use up to an ounce of the drug for personal use.

Whether 21 remains the legal age, though, could be determined by the state Legislature, which is expected to consider making a series of changes to the law approved by voters in November. Among those changes could include raising the minimum age to 25, an idea that Senate President Stanley Rosenberg, D-Amherst, said on Wednesday he will suggest.

“I feel obligated to raise what we’ve been told by brain researchers, and neurological scientists, that the brain is not fully developed until 25, and that heavy use of a product can cause significant concern,” Rosenberg said in a phone interview.

Rosenberg broached the subject of changes that may be made to the marijuana law during an interview on the Boston Herald’s radio program Tuesday, saying it is among the ideas he will bring up with his caucus, as well as House Speaker Robert DeLeo and Gov. Charlie Baker.

As passed by voters, Question 4 allows adults 21 and older to legally possess and use up to 1 ounce of marijuana beginning Thursday, and permits growing up to 12 marijuana plants per household for personal use.

Terry Franklin, a longtime activist in Amherst who has supported legalizing marijuana, said that both legislators and the public should take a critical eye to marijuana health studies, observing that he is concerned with politicians using what he calls “pseudoscience,” or “mumbo -jumbo,” as the basis for decisions.

“There’s nothing I’ve read that says cannabis affects the brain’s development,” Franklin said.

Despite the publicity surrounding Rosenberg’s comments, he said he has received little reaction, and notes that 21 is the legal age to use marijuana in all other places where it has been legalized, such as Colorado.

“I honestly don’t expect it will change anyone’s mind,” Rosenberg said.

Rosenberg and DeLeo earlier this week said they wouldn’t tinker with the current law before it goes into effect.

“The voters spoke in favor of legalized recreational marijuana on November 8th and we fully intend to respect the will of the voters,” they said in a statement. “While we analyze the provisions of the new law and its implementation we will not be passing legislation that changes the December 15th effective date for possession, use and home growing.”

Addressing inadequacies

Still, Rosenberg said it is a “very high priority” for the Legislature to address inadequacies he sees in the law. The Senate president is concerned that the law fails to address limits on the potency of THC, which is the psychoactive chemical in marijuana, particularly in edibles and beverages.

He’s also concerned that there are no regulations covering the advertising and packaging that might make them attractive to children, and there is no standard for legally determining when someone is “driving while high.”

“That is an area that’s not fully developed anywhere,” Rosenberg said.

These are among serious questions, along with whether the tax rate will cover all administrative expenses associated with the public safety and public health for people using marijuana.

State Rep. Peter Kocot, D-Northampton, said he has similar worries, especially since the law was not vetted by legislators. One of the areas he is looking at is those well under 21.

“The focus I’m looking at primarily is how to make sure children, elementary and middle school ages, whose brains are still developing, don’t have access to these products,” Kocot said.

Attending a meeting of the SPIFFY Coalition Wednesday, Kocot said there is a desire to keep powerful strains of marijuana and its byproducts out of the hands of children.

Incoming State Rep. Solomon Goldstein-Rose, D-Amherst, said the adopted law needs to be improved, though he hasn’t given consideration to whether the age should remain at 21, or be increased to 25. He is 23.

Goldstein-Rose said, though, that the law needs to be clear about making sure marijuana isn’t more readily available for juveniles.

“My priority is decreasing access to kids and teens,” Goldstein-Rose said.

While Franklin said he supported the ballot question, he had concerns about business interests writing its language, and worries about proposed changes, whether it be raising the age or increasing the tax associated with it.

“None of the tweaks I’ve heard about are things I like,” Franklin said.

Though the law focuses on personal use, Goldstein-Rose said he would also like to see amendments to the law that will allow farmers to grow agricultural hemp, acknowledging there may be issues with this at the federal level, where marijuana remains illegal.

Kocot said prevention specialists and law enforcement representatives should be part of the Cannabis Advisory Board as it makes recommendations regarding marijuana law.

Scott Merzbach can be reached at smerzbach@gazettenet.com

Scott Merzbach is a reporter covering local government and school news in Amherst and Hadley, as well as Hatfield, Leverett, Pelham and Shutesbury. He can be reached at smerzbach@gazettenet.com or 413-585-5253.