Formaldehyde

OVERVIEW

Formaldehyde (for-MAL-duh-hide) is a colorless, flammable gas with a strong, pungent odor that tends to polymerize readily. Polymerization occurs when individual molecules of formaldehyde combine with each other to make very large molecules called polymers. Over 4 billion kilograms (10 billion pounds) of formaldehyde were produced in the United States in 2004, the vast majority of which was used in the production of plastics and other polymers. To make handling and shipping easier and safer, the compound is usually provided as a 37 percent solution of formaldehyde in water to which has been added an additional 15 percent of methanol (methyl alcohol) to prevent polymerization.

KEY FACTS

OTHER NAMES:

Methanal; oxomethylene; oxomethane; methylene oxide; formic aldehyde

FORMULA:

HCHO

ELEMENTS:

Carbon, hydrogen, oxygen

COMPOUND TYPE:

Aldehyde (organic)

STATE:

Gas

MOLECULAR WEIGHT:

30.03 g/mol

MELTING POINT:

−92°C (−130°F)

BOILING POINT:

−19.1°C (−2.38°F)

SOLUBILITY:

Very soluble in water, alcohol, ether, and benzene

Formaldehyde was first produced accidentally in 1859 by the Russian-French chemist Alexander Mikhailovich Butlerov (1828–1886). It was first synthesized in 1867 by the German chemist August Wilhelm von Hofmann (1818–1892) who was not, however, able to collect the compound in pure form. That step was accomplished by German chemist Friedrich August Kekulé (1829–1896) in 1892.

HOW IT IS MADE

Formaldehyde occurs naturally in the atmosphere at a concentration of about 10 parts per billion (0.000 001%) partly as a by-product of plant and animal metabolism, and partly as a product of the reaction of sunlight with methane (CH₄), a much more abundant component of the air. At such low concentrations, it is not a natural source of the compound for commercial or industrial uses and is produced instead by the oxidation of methanol (methyl alcohol; CH₃OH) or gases extracted from petroleum (such as methane) over a catalyst of silver, copper, or iron with molybdenum oxide.

COMMON USES AND POTENTIAL HAZARDS

By far the most important application of formaldehyde is in the production of polymers and other organic chemicals. About one-quarter of commercial-use formaldehyde is used each year to make a family of polymers known as urea-formaldehyde resins, which are used to make dinnerware, particle board, fiber board, plywood, flexible foams, and insulation. Another 16 percent goes to the production of phenol-formaldehyde resins, with applications in molded and cast plastics, adhesives and bonding materials, laminating materials, brake linings, chemical equipment, machine housing, and a host of other applications. Smaller amounts of formaldehyde are used to make a variety of important chemicals including 1,4-butanediol, methylene diisocyanate, pentaerythritol, and hexamethylenetetramine. Other applications include use in controlled release fertilizers, in the production of nitroparaffin derivatives, in the treatment of textiles, and in the preservation of biological specimens. The last of these uses is probably well known to biology students; its use depends on the fact that formaldehyde kills most types of bacteria and can be used, therefore, to keep biological materials from decaying.

Formaldehyde poses a number of health hazards to humans and other animals. It may cause difficulty in breathing, headaches, fatigue, and lowered body temperature. At high levels of concentration or over long periods of exposure, formaldehyde can induce coma and death. Chronic exposure to formaldehyde is thought to be carcinogenic, producing tumors in the nose, throat, and respiratory system. People who work in factories where formaldehyde is used are at greatest risk for formaldehyde poisoning.

Interesting Facts

• Formaldehyde was one of the first organic compounds to have been discovered in outer space.
• When some vegetables, such as cabbage and brussel sprouts are cooked, they emit small amounts of formaldehyde.

Formaldehyde is now known to be a potentially serious indoor air pollutant. So many products in a home contain formaldehyde that significant levels of the compound may accumulate in a house. The primary sources of the formaldehyde are pressed wood products such as plywood and particleboard; furnishings; wallpaper; and durable press fabrics.

Words to Know

CARCINOGEN

A chemical that causes cancer in humans or other animals.

CATALYST

A material that increases the rate of a chemical reaction without undergoing any change in its own chemical structure.

METABOLISM

A process that includes all of the chemical reactions that occur in cells by which fats, carbohydrates, and other compounds are broken down to produce energy and the compounds needed to build new cells and tissues.

POLYMER

A compound consisting of very large molecules made of one or two small repeated units called monomers.

FOR FURTHER INFORMATION

"About Formaldehyde." Formaldehyde Council. http://www.formaldehyde.org/about_what.html (accessed on October 10, 2005).

"Formaldehyde (Methyl Aldehyde) Fact Sheet." Australian Government; Department of the Environment and Heritage. http://www.npi.gov.au/database/substance-info/profiles/45.html (accessed on October 10, 2005).

Gullickson, Richard. "Reference Data Sheet on Formaldehyde." Meridian Engineering & Technology. http://www.meridianeng.com/formalde.html (accessed on October 10, 2005).

"An Update on Formaldehyde-1997 Revision." U.S. Consumer Product Safety Commission. http://www.epa.gov/iaq/pubs/formald2.html (accessed on October 10, 2005).

See AlsoUrea

FORMALDEHYDE

Formaldehyde is a simple, highly reactive hydrocarbon that is used as a fixative in the pathology laboratory, as a fumigant, and in the manufacture of foam insulation, cosmetics, drugs, clothing, and furniture. It is also a major toxic component of photochemical smog. Formaldehyde is a strong allergen and irritant to which humans have a very low odor threshold (less than 1 ppm), and it is carcinogenic in the rat bioassay via the inhalation route. Formaldehyde increases airway resistance when inhaled, probably because of local irritation and release of inflammatory mediators. Additionally, formaldehyde is a strong contact allergen. Both pulmonary changes and dermatologic symptoms have been reported in the occupational setting. Acute and chronic dermatitis was once a common complaint in the beauty parlor industry because of using formaldehyde in fingernail finishes. Histology and pathology laboratories were common sites of high levels of exposure. However, after the report of nasal tumors in rats, industrial hygiene measures were instituted to minimize exposure. This was also true in the garment industry, where formaldehyde was used in the manufacture of permanent press fabrics.

Formaldehyde residues are major constituents of smog. An overwhelming percentage of the aldehyde in smog is formaldehyde. It is through smog that the general population is most broadly exposed. Because of its irritant and allergenic properties, formaldehyde is considered one of the possible etiologic agents involved in the well-documented asthma incidents that have occurred in relation to moderate to severe smog events. Another source of exposure to the general public in indoor air is off-gassing from fabrics and foam materials. These levels are considerably lower than photochemical smog concentrations, but they are more insidious because of the ambient nature of the exposure. In house fires, formaldehyde residues in fabrics and foams play a major role in the toxicity of smoke.

The greatest risk for injury from formaldehyde is in a workplace with minimal industrial hygiene measures. The greatest danger of formaldehyde is to those individuals who have compromised pulmonary function.

Michael Gallo

(see also: Ambient Air Quality [Air Pollution]; Asthma; Occupational Safety and Health )

form·al·de·hyde / fôrˈmaldəˌhīd; fər-/ • n. Chem. a colorless pungent gas, CH₂O, in solution made by oxidizing methanol.

formaldehyde (for-mal-di-hyd) n. the aldehyde derivative of formic acid, formerly used as a vapour to sterilize and disinfect rooms and such items as mattresses and blankets. The toxic vapour is produced by boiling formalin in an open container or using it in a sealed autoclave.

formaldehyde Alternative name for methanal