There are a number of hazards associated with the use of formalin. It readily releases formaldehyde gas, which is both toxic and highly flammable. Accidental spillage of the solution can quickly raise the concentration of this gas to dangerous levels, posing a direct threat to health and the risk of fire or explosion.
Formaldehyde may be present in food artificially through contamination or in nature. Ingestion of formaldehyde may cause corrosion in the gastrointestinal tract. It may also cause ulcers and inflammation in the mouth, stomach and intestine ,tongue and esophagus causing pain, vomiting and bleeding. Severe exposure to formaldehyde through ingestion may cause abdominal pain, diarrhea and possible hemorrhage in the stomach or intestines. If you frequently eat foods that are preserved with formalin, it will cause irritation to the stomach so the blood can cause vomiting, rapid breathing, yellowish discoloration of the skin or diarrhea mixed with blood, urine or blood and could also potentially cause death. But this rarely happens, because it required a large dose of formalin.
Some studies of humans exposed repeatedly to formaldehyde in workplace air found more cases of nose and throat cancer than expected. Animal studies of laboratory rats exposed for life to formaldehyde in air found that some rats developed