Formaldehyde is the simplest aldehyde with chemical formula CH2O and molecular weight 30.03 g/mol. It is colorless, strong-smelling in gaseous form called as Methanal, Methyl aldehyde, Methylene oxide and in aqueous form as Formalin (37 to 50% formaldehyde by weight, which usually contains 6 to 15% methanol as stabilizer). At STP the formaldehyde melts at ?92°C, boils at ?21°C, and is soluble in water, alcohol, and ether.
Structure of Formaldehyde (HCHO):
It is a strong reducing agent, especially in the presence of alkalis, and is incompatible with ammonia, alkalis, tannin, bisulfides, iron preparations, copper salts, iron salts, silver salts, iodine and potassium permanganate. It combines directly with albumin, casein, gelatin, agar and starch to form insoluble compounds. It reacts violently with nitrous oxides at about 1800C, (HClO4 + aniline), performic acid, nitromethane, manganese carbonate and hydrogen peroxide . It reacts with strong oxidizers and acids. It is also incompatible with phenols.
Formaldehyde may become cloudy upon standing, especially at cool temperatures. It slowly oxidizes in air. It is sensitive to exposure to light. It is polymerized in aqueous solutions if unstabilized. Solutions of it in water, DMSO, 95% ethanol or acetone should be stable for 24 hours under normal lab conditions.
Formaldehyde is naturally produced in small amounts in our bodies. Commercially it is prepared by passing methanol vapor mixed with air over a catalyst, e.g., hot copper, to cause oxidation of the methanol; it is also prepared by the oxidation of natural gas. It forms formic acid when it is oxidized. Commercial formulations generally consist of a 37% by weight solution of formaldehyde in water with 10-15% methanol added as a stabilizer.
Formaldehyde can be used for many purposes and is a popular chemical because of its low cost. It is used as a preservative for biological materials, disinfectant and antiseptic, in embalming solutions and in the manufacture of phenolic resins such as Bakelite, artificial silk, cellulose esters, dyes, urea, thiourea, melamine resins, organic chemicals, glass mirrors and explosives. Formaldehyde was a component in urea formaldehyde foam insulation (UFFI).It is also used in improving fastness of dyes on fabrics, in as a germicide and fungicide for vegetables and other plants, in preserving and coagulating rubber latex and to prevent mildew in wheat and rot in oats. It is used to render casein, albumin, and gelatin insoluble, in chemical analysis, as a tissue fixative, as a component of particle board and plywood and in the manufacture of pentaerythritol, hexamethylenetetramine and 1,4-butanediol. It is also used in photography for hardening gelatin plates and papers, for toning gelatin-chloride papers and for chrome printing and developing
Formaldehyde is normally present at low levels, usually less than 0.06 ppm (parts per million), in both outdoor and indoor air. When present in the air at levels at or above 0.1 ppm, acute health effects can occur including watery eyes; burning sensations in the eyes, nose and throat; nausea; coughing; chest tightness; wheezing; skin rashes; and other irritating effects. Formaldehyde can affect people differently. Some people are very sensitive to formaldehyde while others may have no noticeable reaction at the same level of exposure. Sensitive people can experience symptoms at levels below 0.1 ppm. The World Health Organization recommends that exposure should not exceed 0.05 ppm. Colds, flu, and allergies can cause symptoms similar to some of those produced by exposure to formaldehyde.
Drinking large amounts of formaldehyde can cause severe pain, vomiting, coma, and possible death. Formaldehyde dissolves easily but does not last a long time in water. Most formaldehyde in the air breaks down during the day. The breakdown products of formaldehyde are formic acid and carbon monoxide (ATSDR, 1999). Formaldehyde does not build up in plants and animals.
Sources that influence indoor levels of formaldehyde can be divided into two broad categories: combustion and off-gassing. Combustion sources include cigarettes and
other tobacco products, and open fireplaces. Off-gassing sources include wood products such as particle board and other building materials made with adhesives containing formaldehyde as well as some varnishes, paints, carpeting, drapes and curtains (WHO 1989).
Formaldehyde has caused cancer in laboratory animals and may cause cancer in humans. The U.S. Environmental Protection Agency (EPA, 1989) classified formaldehyde as a probable human carcinogen under conditions of unusually high or prolonged exposure. Since that time, some studies of industrial workers have suggested that formaldehyde exposure is associated with nasal cancer and unsparing cancer, and possibly with leukemia. In 1995, the International Agency for Research on Cancer (IARC) concluded that formaldehyde is a probable human carcinogen. However, in a reevaluation of existing data in June 2004, the IARC reclassified formaldehyde as a known human carcinogen. There is no known threshold level below which there is no threat of cancer. The risk depends upon amount and duration of exposure. Kulle (1993) reported that a one-hour exposure limit is established at 123 µg/m3 (100 ppb), which represents one fifth of the no observable adverse effects level and one tenth of the lowest observable adverse effects level found for eye irritation, and a eight-hour exposure limit is established at 50 µg/m3 (40 ppb), i.e., a the lower end of the exposure category associated with no significant increase of asthma hospitalization (Rumchev, et al., 2002).
At the end of 2003, there are approximately 11,900 formaldehyde and derivative plants operating in the United States and Canada, with nearly all states and provinces represented. Production of formaldehyde in the United States in 2003 amounted to 4.33 million metric tons; production in Canada amounted to 775,000 metric tons. The value of sales of formaldehyde and derivative products amounted to $145 billion-plus. This represents 1.2% of the Gross Domestic Product (GDP) of the United States and Canada.
Agency for Toxic Substances and Disease Registry (ATSDR). 1999. Toxicological profile for formaldehyde. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Services.
International Agency for Research on Cancer (June 2004). IARC Classifies Formaldehyde as Carcinogenic to Humans. Retrieved June 30, 2004, from: http://www.iarc.fr/ENG/Press _Releases/archives/pr153a.html.
Kulle, T.J. (1993). Acute odor and irritation response in healthy nonsmokers with formaldehyde exposure. Toxicol. Ind. Health 5: 323–332.
Rumchev, K.B., Spickett, J.T., Bulsara, M.K., Phillips, M.R., and Stick, S.M. (2002). Domestic exposure to formaldehyde significantly increases the risk of asthma in young children. Eur. Respir. J. 20: 403–406.
U.S. Environmental Protection Agency, Office of Air and Radiation. (1989).Report to Congress on Indoor Air Quality, Volume II: Assessment and Control of Indoor Air Pollution.
WHO. (1989). Formaldehyde. Environmental Health Criteria 89. Geneva: World Health Organization, International Programme on Chemical Safety.
Economic Primer on Formaldehyde, Global Insight, Inc. 2006