GENEVA - A human rights investigator for the United Nations says up to a quarter of the world's trash from hospitals, clinics, labs, blood banks and mortuaries is hazardous and much more needs to be done to regulate it. Calin Georgescu, a U.N. special rapporteur, says few nations are developing the rules needed to cope with the growing mountains of medical waste that pose a hidden risk of infection and could expose people to low levels of radioactivity and needle-stick injuries.