Children with levels of lead in their blood that are now considered safe scored significantly lower on intelligence tests than children with almost no lead in their blood, according to a study presented yesterday at the Pediatric Academic Societies annual meeting. Lead author Bruce Lanphear said the research suggested that one in every 30 children in the U.S. has been negatively affected by lead. Currently, 10 micrograms of lead per deciliter of blood is considered a safe concentration level, but experts predicted that Lanphear’s research would cause regulators to lower the standard.