From China Digital Space
地沟油 (dìgōu yóu): ditch oilit can be carcinogenic and contain hazardous chemicals.
Ditch oil first became a topic of major concern in 2010, when authorities revealed that up to one-tenth of cooking oil used in China might actually be ditch oil. Ongoing investigations have shown that ditch oil is widely used. Ditch oil is now a symbol of China’s ongoing food safety issues. A 2012 study by the Pew Research Center found that 41% of Chinese considered food safety a very big problem for the country, up from just 12% in 2008.