GRAND RAPIDS, MI - Police, prosecutors, health officials and others across the state warned of dangers if a ballot initiative to legalize recreational use of marijuana is passed by voters in November.

Opponents of legalized marijuana say it would become more accessible to children and harm their development, create danger on the roads and increase mental-health issues.

"There's so many things involved with this," Ottawa County Sheriff Steve Kempker said Tuesday, Sept. 19, at Wyoming Department of Public Safety.

"It's clearly going to change the landscape of Michigan. It's going to change the landscape of our communities," Kempker said.

He spoke during one of the six press conferences held across the state by police leaders, prosecutors, health officials and educators.

Legalization advocates accused the opponents of using scare tactics that "conflict with most scientific research on the issue."

The Coalition to Regulate Marijuana Like Alcohol, or CRMLA, which formed to support the ballot proposal, issued a statement to "refute the baseless or exaggerated claims made by law enforcement ... ."

"We encourage an open and honest debate on this important issue," spokesman John Truscott said.

"Unfortunately, that's not what we see from some who have chosen to confuse the public with dubious or contested statistics rather than discuss facts. The fact is that marijuana prohibition has been a complete failure and a waste of law enforcement resources - regulation and taxation provide a far better alternative."

Kempker, the Ottawa County sheriff, said he recently met with law-enforcement officials in Colorado where marijuana has been legal since the start of 2014. He said that homelessness, petty theft and drugged-driving crashes - with marijuana the main drug - have increased.

Mostly, he's concerned about the impact on children, and their easier access to the drug.

Joan Hoganson, director of Kent County Health Department's Community Wellness Division, said easier access will bring increased use, particularly among children.

She said efforts to help children grow up healthy and succeed in life "will be sabotaged if we make recreational marijuana a possibility for young people whose brains are still in formation."

Ross Buitendorp, director of network administration at Network180, said mental-health officials are concerned about an increased use in marijuana. States that have legalized the drug have seen an increase number of those seeking substance-abuse treatment for marijuana.

The Network180 Board of Directors in Grand Rapids passed a resolution that said "direct associations have been made between the frequency of marijuana use and higher potency with development of mental issues - psychosis, depression, anxiety, suicidality, reshaping of the brain, and addiction."

Muskegon County Prosecutor D.J. Hilson said: "This substance is turning a working class of people into unemployable because they cannot pass a drug test or stay clean on the job."

He said that black markets for marijuana continue to thrive in states that have legalized the drug.

Ottawa County Prosecutor Ron Frantz said the legalizing marijuana would not, as some say, open jail cells for violent offenders. Any notion that the nation's jails and prisons are filled with those convicted marijuana-related crimes is "fallacy," Frantz said.

He thinks that drugged driving would increase.

"It's a terrible idea for Michigan," Tuscola County Prosecutor Mark Reene said.

"We're not forced to do this in a vacuum. We know what's happening in other states. The same exact thing will happen here."

Nine states and Washington, D.C., allow recreational use of marijuana but Reene noted Michigan would be the first in the Midwest.

Kent County Prosecutor Chris Becker said many would be attracted to Michigan because the proposal would allow possession at home of up to 10 ounces of marijuana, compared to a standard one ounce. The proposed 10-percent excise tax would be among the lowest in the country.

He said people in neighboring states would visit Michigan to get marijuana and bring it home.

Truscott, the legalization advocate, said that under the proposed law, communities would have "complete control" over marijuana businesses, and businesses would be banned from marketing products that would be attractive to youth.

Several violations would be lowered from crimes to civil infractions, which would save millions for the state's legal system. It would also increase job opportunities by those who otherwise would have a criminal record.

He accused law enforcement of "fearmongering."

He said that Colorado and Washington, which allow recreational marijuana, have accident rates similar other states. The use rate among youth has remained stable after marijuana was legalized, Truscott said.