AUGUSTA — Jessica Graham, a mother of two from Waterville, said Thursday that parents shouldn’t have to spend a lot of time in the grocery aisle trying to determine whether the foods they are buying for their children may contain a chemical called bisphenol-A.

“Even though I have spent hours researching it, it is very difficult to know,” she said. “No child should be exposed to toxic chemicals like BPA at the dinner table, and no parent should have to worry that the food they give their children is unsafe.”

Graham was one of about 40 mothers who gathered at the Augusta Civic Center for a press conference on a proposed rule that would ban BPA from infant and toddler food containers, including jars and cans. The mothers spoke during a break in a day-long public hearing on the rule.

In the morning, environmental groups faced off with industry as state regulators considered an expanded ban on BPA, a chemical used in hardened plastics that is sometimes found in infant and toddler food containers.

On one side, scientists, physicians and others said the chemical should be banned from infant and toddler food containers because it has been linked to cancer, obesity, learning disabilities and hormone problems.

“The proposed rule before you will protect the health of Maine toddlers,” said Michael Belliveau, who spoke on behalf of the Alliance for a Clean and Healthy Maine, an umbrella organization that includes the Environmental Health Strategy Center and Natural Resources Council of Maine.

On the other side, the Maine State Chamber of Commerce and the Grocery Manufacturers Association said there’s no need for Maine to move swiftly ahead with an expanded ban. Maine has already banned the chemical from baby bottles, sippy cups and other reusable food and beverage containers.

“Contrary to what some claim, there is no across-the-board replacement for BPA in can linings,” said Jim Mitchell, who testified on behalf of the grocery manufacturers. “As opposed to jumping ahead of important ongoing work of the Food and Drug Administration and the National Institutes of Health, we are hopeful the board’s decision-making will await additional scientific evidence.”

Staffers at the Maine Department of Environmental Protection, including Commissioner Pattie Aho, and members of the Board of Environmental Protection, held a joint hearing Thursday at the Augusta Civic Center as part of its consideration of a citizen-initiated petition that calls for the expanded ban.

In June, environmental activists turned in more than 800 signatures calling for more regulations.

For nearly four hours Thursday, the joint panel heard expert testimony from both sides, much of it focused on finer points of the proposal. Later in the day, mothers — including former House Speaker Hannah Pingree, D-North Haven — were expected to testify on behalf of the proposal.

Aho pressed the experts who testified to explain how her agency would be able to effectively monitor and regulate the sale of cans and jars of baby and toddler food.

“We’re environmental regulators,” she said. “You’re asking us to be the FDA in some regards here.”

Three other states — Connecticut, Vermont and Maryland — have similar bans on BPA in infant formula or baby food, and the study of the chemical is “an area of explosion in science,” said State Toxicologist Andrew Smith.

“There is an enormous amount of literature coming out on this chemical,” he said.

Those pushing for the expanded ban said there’s clear evidence BPA is harmful to animals and that there is emerging science about its effects on humans. Dr. Deborah Rice, a toxicologist who retired earlier this year from the Maine Center for Disease Control, said there should be no controversy surrounding the issue.

“To me, it is a logical extension of what the board already did (with the ban on sippy cups),” she said during a press conference held by supporters.

Opponents say the original ban enacted in 2010 and changes approved in 2011 were agreed to by all parties, including the state chamber and environmentalists. Now, they say the citizen initiative violates that process.

“The current citizens initiative does an end run around this process and intentionally disregards the will of the Legislature and the spirit of the compromise of 2011,” said Ben Gilman of the chamber. “This initiative further muddies an uncertain regulatory climate and circumvents the intent and spirit of the legislative process. In short, it threatens to undermine the Legislature and create uncertainty amongst small businesses.”

State regulators will continue to accept public comments on the proposed rule until Sept. 28. After that, the DEP will consider all the public input and make a recommendation to the board.