Smoking can be done by either cold smoking or hot smoking. Pastrami evolved from the Turkish Huns who would tenderize and dry meat under their saddles. Armenians saw what the Huns had done and created basturma that was spiced and air-dried meat. Romanians first started brining, spicing, and smoking the beef and created what is now called pastrami. When Romanian Jews immigrated to the United States, Canada, and Great Britain in the late 1800s, they carried that tradition of pastrami with them. The Romanians that immigrated to the United States, mostly settled in New York City area and developed the classic New York Pastrami. Those that immigrated to Canada mostly settled in Montreal used a different brining technique and spices and called it smoked meat. Pastrami is still produced in Southwest Asia and the Middle East and is called Pastirma, basterma or basturma. While customarily made with beef, in other regions it can be made with lamb, goat, buffalo, and camel. Corned or salt beef uses a similar brine and spices, but is not smoked. Zhangcha duck is a dish from Sichuan Province in southwestern China made from the Chengdu Ma duck. The duck is marinated in a pickling liquid then smoked with camphor and tea leaves. After smoking, the duck is deep fried, boned and served over rice. One study has shown an association between the frequency of consumption of smoked foods and intestinal cancer. However, the study was restricted to a small Slovenian population in Hungary, where the local smoke curing process produces levels of contaminants roughly eight times as high as standard processes elsewhere. Smoked meats have the potential for promoting the growth of "Listeria" bacteria. "Listeria monocytogenes" can also cause serious neonatal infection and can be transmitted from mother to child before or after birth. The infection can cause serious harm or even infant death. The use of soft woods is discouraged, as the resins in softwood increases the concentration of polycyclic aromatic hydrocarbons (PAHs) that are known carcinogens.