Massachusetts employers oppose by a wide margin a pending ballot question that would legalize the recreational use of marijuana in the commonwealth.

Sixty-two percent of 180 employers responding to the special question on the March Associated Industries of Massachusetts Business Confidence Index Survey 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.

AIM opposes the question because the legalization of marijuana in Massachusetts would create considerable uncertainty for employers relative to their legal rights and obligations, particularly with workplace drug policies. These employers would operate in an environment in which state law permits private use of marijuana, while federal law, which is often the overriding jurisdiction in employment scenarios, prohibits marijuana use.

“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.”

Another issue is that many companies receive favorable workers’ compensation insurance rates by declaring themselves to be drug-free workplaces. That status may be substantiated only through drug testing employees. Even if employees are, on their personal time, using drugs legal in their state, if those drugs are indicated on their drug tests, their workplace would lose those favorable insurance rates.

Recent surveys have 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.

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.