A proposed law on the November ballot to legalize and commercialize marijuana in Massachusetts would reverse decades of hard-won progress by employers to create safe and drug-free workplaces.

Question 4 would place employers in the untenable position of determining whether an employee who tests positive for marijuana, used legally under state law, is too impaired to operate a machine or drive a company vehicle safely. It would also create a legal nightmare for employers caught between a state law that permits private use of marijuana and a federal law – often the overriding jurisdiction in employment scenarios – that prohibits marijuana use.

That’s why the Board of Directors of AIM has joined an extraordinary coalition of public officials, civic leaders and businesses urging a “no” vote on Question 4. The coalition includes Governor Charlie Baker; House Speaker Robert DeLeo; Boston Mayor Martin J. Walsh; Attorney General Maura Healey; Members of Congress Joe Kennedy, III, Stephen Lynch, Nikki Tsongas and William Keating; Cardinal Se��n P. O’Malley and the Roman Catholic Bishops of Massachusetts; the Massachusetts Hospital Association; the Massachusetts Medical Society; and the Massachusetts Municipal Association

A survey conducted by AIM earlier this year indicates that employers oppose Question 4 by a wide margin.

Sixty-two percent of employers said they would vote “No” on the pot legalization referendum due to appear on the November 1 ballot. Thirty-eight percent were in favor.

The proposed ballot law would authorize individuals 21 and over to possess up to one ounce of marijuana outside of their home and up to ten ounces of marijuana in their residences. It calls for taxes on marijuana sales and creates a Cannabis Control Commission to handle regulation and licensing.

If approved, the new law would take effect on December 15.

“We’re not surprised by the poll results given the concerns being expressed to us by member employers,” said John Regan, Executive Vice President of Government Affairs at AIM.

“How will an employer respond to a worker operating heavy equipment on a job site under the influence of marijuana? Many jobs, particularly those in safety-sensitive fields like transportation or manufacturing, must adhere to federal regulations that still prohibit the use of any substance that creates impairment.”

In fact, no breathalyzer-type technology exists to measure the degree of impairment suffered by a marijuana user. Question 4 not only fails to establish an enforceable legal standard as exists in other states, but also fails to establish a standard by which employers may terminate or discipline an employee who may have used marijuana and could be a safety risk on the job.

The potential consequences are significant.

In Colorado, which legalized medical marijuana in 2010 and recreational marijuana in 2012, marijuana-related traffic deaths increased by 154 percent between 2006 and 2014. Emergency room hospital visits that were “likely related” to marijuana increased by 77 percent from 2011 to 2014; and drug-related suspensions/expulsions increased 40 percent from school years 2008/2009 to 2013/2014, according to a September 2015 report by the Rocky Mountain High Intensity Drug Traffic Area, a collaboration of federal, state and local drug enforcement agencies.

Recent surveys have also indicated an increase in general marijuana use when states approve the legalization of marijuana. According to the National Survey on Drug Use and Health, between 2012 and 2013 (when marijuana was legalized but states had yet to implement a regulatory framework) the percentage of adults who reported using marijuana jumped by more than 20 percent in Washington and Colorado.

Employers remain concerned that much of the increased marijuana usage in these states has come from high-potency edibles – THC-infused candy bars, gummies, cookies and soda ” many packaged to look like candy and snacks. Almost half of all marijuana sales in Colorado, which was the first state to legalize, now come from edibles and concentrates.

The appeal of edible marijuana products to teen-agers is an issue for medical and behavior health organizations like the Massachusetts chapter of the National Alliance on Mental Illness (NAMI), and the Association for Behavioral Healthcare.

“The research shows that marijuana poses a risk for the young brain ” those 25 and under ” that is predisposed to emotional and mental health issues,” said NAMI Mass Executive Director Laurie Martinelli.

Marijuana legalization is among a handful of November ballot questions with implications for employers. AIM favors a proposal to lift the cap on charter schools and opposes questions that would end the use of Common Core educational standards and impose de-facto government price controls on hospitals.

AIM also opposes a proposed constitutional amendment that would impose a 4 percent surtax on income more than $1 million that could reach the ballot by 2018.