One study concluded that epidemiological evidence is consistent with an increased risk of birth defects in the offspring of persons exposed to DU. Environmental groups and others have expressed concern about the health effects of depleted uranium, and there is some debate over the matter. Some people have raised concerns about the use of this material, particularly in munitions, because of its mutagenicity, teratogenicity in mice, and neurotoxicity, and its suspected carcinogenic potential. Additional concerns address unexploded DU munitions leeching into groundwater over time.