Let see what happen to your body if you consume ‘enough’ formalin: =P
“Because formaldehyde resins are used in many construction materials, including plywood, carpet, and spray-on insulating foams, and because these resins slowly give off formaldehyde over time, formaldehyde is one of the more common indoor air pollutants. At concentrations above 0.1 mg/kg in air, inhaled formaldehyde can irritate the eyes and mucous membranes, resulting in watery eyes, headache, a burning sensation in the throat, and difficulty breathing.
Large formaldehyde exposures, for example from drinking formaldehyde solutions, are potentially lethal. Formaldehyde is converted to formic acid in the body, leading to a rise in blood acidity, rapid, shallow breathing, hypothermia, and coma or death. People who have ingested formaldehyde require immediate medical attention.
In the body, formaldehyde can cause proteins to irreversibly bind to DNA. Laboratory animals exposed to large doses of inhaled formaldehyde over their lifetimes have developed more cancers of the nose and throat than are usual, as have workers in particle-board sawmills. However, some studies suggest that smaller concentrations of formaldehyde like those encountered in most buildings have no carcinogenic effects. Formaldehyde is classified as a probable human carcinogen by the U.S. Environmental Protection Agency and as a known human carcinogen by the International Agency for Research on Cancer.” ( taken from Wikipedia , emphasis mine) ( taken from Wikipedia , emphasis mine)
So to prevent yourself getting nasty cancer, please eat more vegetables. Should you really need to resort to those meats and fishes, make sure they are fresh. How to make sure the their freshness ? I’ll leave this to those Material/Chemical Engineers to create another practical indicator test device, just like my previous idea of an indicator for the purity of petrol …. (which is never realised …. >.<)