Arab nations are accusing Israel of attacking Gaza with ammunition containing depleted uranium, and they are calling for a UN investigation of reports that traces of the substance has been found in victims of shelling carried out Operation Cast Lead. The nations appear to be alluding to concerns of a health hazard through radiation emitted by depleted uranium, which makes munitions harder and more effective. The IAEA says the material is potentially carcinogenic, but says long-term studies have not definitely established that. The allegations were made in a letter Monday written on behalf of Arab ambassadors accredited in Austria and made available to The Associated Press. It expresses concern about alleged information that traces of depleted uranium have been found in Palestinian victims.