The group argues that the toxic herbicides run off into surface and ground water, polluting drinking water and posing a health risk to humans and the environment. The group is asking the state to use organic herbicides or manual means, such as string trimmers and lawnmowers.

But state officials say affected areas are in small, controlled environments. Using workers to trim vegetation along busy highways, they argue, poses a greater danger.

“We’re not spreading it into a sensitive area,” said Erik Abell, a spokesman for the Massachusetts Highway Department.

Until 2003, the state controlled all its roadside vegetation manually. Since then, MassHighway has used herbicides to treat a small number of roadsides around mostly medians and guardrails. Several legislators who signed on to the campaign said the state should use nontoxic herbicides as a precautionary measure.

“I just think you can’t exercise too much caution,” said state Representative Sarah Peake, a Democrat who represents several towns on Cape Cod.

“When I was a child, DDT was thought to be safe,” she said. “And now we know better.”

State Representative Peter V. Kocot, a Democrat from Northampton, said he does not use herbicides on his lawn and is not certain whether spraying for turf control and management is a prudent use of state resources.

“In addition, the use of herbicides in numerous studies has been shown to have an adverse impact not only on the human population, but birds and wildlife,” Kocot said.