Amid growing concern that flame retardants are responsible for elevated cancer rates in firefighters, Massachusetts lawmakers are pushing legislation that would go further than any other state’s in banning the use of chemicals meant to slow the spread of fires. Fire officials and environmental advocates, who have joined forces to support the restrictions, contend that at least 10 chemicals used in flame retardants endanger firefighters, while doing little to stop fires. They support two bills that would prohibit manufacturers and retailers from using the chemicals in children’s products and upholstered furniture and authorize state environmental officials to ban other retardants they designate as health risks. “This is a vital public safety matter that we should be addressing,” said state Senator Cynthia Creem, a Newton Democrat who sponsored one of the bills. “As the industry has become aware of the risks, we need to do more to protect our families and firefighters.”