Wal-Mart Stores Inc., the world's largest retailer, said on Wednesday it will set new quality standards for its suppliers amid a scare over toxic milk products that have sickened tens of thousands of babies across China . Meanwhile, the United Nations released a report that recommends China increase oversight of its food safety system and hold businesses accountable for their products. Mike Duke, vice chairman of Wal-Mart's international division, said the company is expecting "greater transparency...from our supplier partners" beginning next month.