Activists who think the state’s proposed ban on a chemical found in baby bottles and sippy cups doesn’t go far enough testified at a hearing last week. Members of the Alliance for a Healthy Tomorrow are pushing for regulations that would further restrict the presence of bisphenol A. The chemical is used in a variety of products, including plastic bottles and the linings of canned food containers. Studies of laboratory animals suggest the chemical could cause developmental problems for children if they are exposed to small quantities early in life. Alliance members want the state to prohibit BPA in packaging for infant formula and baby food as well as all reusable food and beverage containers. The Deval Patrick administration has proposed banning baby bottles and toddler sippy cups containing the chemical. “If the Department of Public Health allows a BPA regulation to pass with this limited scope of products, they will be allowing continued toxic contamination of vulnerable infants,’’ Lee Ketelsen, New England codirector of Clean Water Action, said in a statement. The organization is part of the alliance. The US Food and Drug Administration has launched studies of BPA but it has not called for regulatory action. Elizabeth Cooney A greener space in Allston