Formaldehyde was first reported in 1859 by Russian chemist Aleksandr Butlerov (1828–86) and was conclusively identified in 1869 by August Wilhelm von Hofmann. Formaldehyde (systematic name methanal) is a naturally occurring organic compound with the formula CH2O (H-CHO). It is the simplest of the aldehydes (R-CHO). The common name of this substance comes from its similarity and relation to formic acid.
In view of its widespread use, toxicity, and volatility, formaldehyde poses a significant danger to human health. In 2011, the US National Toxicology Program described formaldehyde as "known to be a human carcinogen”.
Formaldehyde does not accumulate in the environment, because it is broken down within a few hours by sunlight or by bacteria present in soil or water.
Humans metabolize formaldehyde quickly, so it does not accumulate, converting it to formic acid in the body. A 37 per cent solution of formaldehyde in water is called as formalin. As formalin is a strong disinfectant and tissue hardener; it's used for preserving biological and anatomical specimens. It is also used as an antiseptic in sterilising surgical instruments.
Formaldehyde is an important precursor to many other materials and chemical compounds. Formaldehyde-based materials are key to the manufacture of automobiles, and used to make components for the transmission, electrical system, engine block, door panels, axles and brake shoes.
When treated with phenol, urea, or melamine, formaldehyde produces, respectively, hard thermoset phenol formaldehyde resin, urea formaldehyde resin, and melamine resin. These polymers are common permanent adhesives used in plywood and carpeting.
Indiscriminate use of toxic substances for preservation of dry and wet fish has triggered panic among public. In Bangladesh and many parts of our country, fishes are adulterated by hazardous chemicals at different steps from farm to consumers.
Formalin (FA) is reported to be frequently added as preservative either by dipping or spraying to the fresh fishes by the fish traders while transporting to domestic marketing chain to prevent spoilage and extend shelf life.
Acceptable daily intake of formalin is 0.2 mg/kg bw/day as according to the United States Environmental Protection Agency. However, formaldehyde is not permitted for use in foods as per Food Safety and Standards Regulations, 2011. Presence of formaldehyde at higher levels can lead to severe abdominal pain, vomiting, coma, renal injury and possible death.
Formaldehyde exists in many animal and plant species as a product of their normal metabolism. Formaldehyde is documented to be present naturally in many common food items, including fruits and vegetables, sea fish, meat, mushrooms etc.
Major manmade sources of formaldehyde include combustion, building materials and tobacco smoke. Globally formaldehyde is identified as one of the top 25 most widely produced chemical substances because of its high reactivity, colourless nature, purity and low cost.
Consumers are advised to wash all food items thoroughly with running tap water, as formaldehyde is soluble in water and washing can aid removal of formaldehyde since formaldehyde is highly water soluble in nature.
The fish purchased from the vendors should be washed thoroughly before cooking. While cooking formaldehyde is also removed since it is volatile in nature.
Generally, formaldehyde is present naturally in marine and brackish water fishes. Any fresh water fish testing positive indicates added formalin. There are several testing methods available for formalin. The Central Institute of Fisheries Technology has developed a rapid detection kit which is simple and user friendly. It detects only added formaldehyde present in the fish.
(Dr Senapati is Professor and Head, Department of Chemistry, Trident Academy of Technology Bhubaneswar. Dr Sahu is Deputy Director cum Food Analyst, State Food Testing laboratory, Bhubaneswar.)