This question was reached by the research director after a long-term investigation. Sichuan is located in a basin with a humid climate, and local people have the habit of using sauerkraut, which is similar to Linxian County, Henan Province.
Through the cooperative research with the National Institutes of Health, nitrosamines-methylbenzyl nitrosamine and Roussin red methyl ester, which have never been found in the world, were isolated from pickled vegetables that Sichuan people like to eat. Many experiments have proved that this nitrosamine can induce tumors in animals.
In the production of sauerkraut, it is easy to produce ammonium nitrate with a little carelessness. There is also mold. If sauerkraut goes bad, it will be even worse.
For mold, it is related to the local natural environment. Basin, damp, weak ultraviolet rays, cold and humid places are easy to mold. Aflatoxin may be present after mildew grows in the east and west. Studies have shown that aflatoxin is highly toxic to humans. Aflatoxin is mutagenic and can lead to non-programmed DNA synthesis of human fibroblasts. Moreover, aflatoxin is a highly toxic carcinogen, in which aflatoxin B 1 can cause cells to repair DNA wrongly, leading to serious DNA mutation, and can also inhibit the synthesis of DNA and RNA, thus inhibiting the synthesis of protein.
This picture is very common in Sichuan.
The older generation is diligent and thrifty, and some moldy food and utensils are reluctant to throw away. Ingestion of mold eventually leads to cancer.
So: there is a conclusion in the question.
To reduce the possibility of esophageal cancer, we should change our living habits appropriately.
Reference link:
Encyclopedia of ammonium nitrate
Identification of nitroso compounds in Chinese sauerkraut by China HowNet.
This page links to the encyclopedia of aflatoxin.