A top environmental group has sued the U.S. Food and Drug Administration over its failure to regulate bisphenol A, a ubiquitous chemical linked to reproductive harm, cancer and obesity in studies. The Natural Resources Defense Council filed a lawsuit [on June 29] in the U.S. Court of Appeals for the D.C. Circuit arguing that millions of Americans have been unnecessarily exposed to the substance - found in everything from soda bottles and tuna cans to children's sippy cups - in the two years since it first petitioned the agency to outlaw bisphenol A. Under the FDA's own rules, it was required to approve, deny or otherwise respond to the October 2008 petition within 180 days, the lawsuit said. After maintaining for decades that bisphenol A was safe, the FDA reversed position in January, saying exposure to the chemical was of "some concern" for infants and children. The FDA also said it would further study bisphenol A over the next two years. "More research is always welcome and interesting, but at some point you have to say, 'We know enough,' and take action. We've reached that point," said Sarah Janssen, senior scientist at the NRDC's Environment and Public Health program in San Francisco.