Those getting off the Massachusetts Turnpike near Chicopee will now get the chance to see a first in state history — billboards advertising medical marijuana.

The two billboards, visible from the east and west near Exit 5, were put up by the medical marijuana nonprofit New England Treatment Access. NETA operates two medical marijuana dispensaries, one in Northampton and another in Brookline.

Along with a billboard in Somerville and another in Boston, they represent the first set of medical marijuana billboards in the commonwealth. All four billboards went up on Monday.

“We want to promote a conversation,” said Norton Arbelaez, director of government affairs for NETA.

That conversation centers on highlighting the desirability of the regulated model of medical marijuana of which NETA’s dispensaries are a part.

Approximately 45,000 people have registered as medical marijuana patients around the state. However, Arbelaez said that, based on numbers from other states, 1.8 to 2 percent of adults use medical marijuana nationally. He also estimated that 100,000 to 150,000 people in Massachusetts use medical marijuana.

Arbelaez said those who don’t get their marijuana from the regulated market get it from the black and gray markets. Black market marijuana is marijuana produced and sold illegally, while gray market marijuana is produced under legal auspices but sold inappropriately, such as caregivers who produce marijuana for people besides their own patient. [Read more at Daily Hampshire Gazette]