Methods for Monitoring in the Environment
Methods for Monitoring Human Exposure
Safeguards Against Acrylamide Exposure
Absorption, Distribution and Metabolism
Primary Sites for Toxicity
Mechanism of Action
Risk Assessment and Management
Introduction to Policy
Decision Makers and Stakeholders
CHARACTERISTICS OF ACRYLAMIDE
Chemical Abstract Number 79-06-1
SYNONYMS: 2-Propenamide, Acrylic acid, Ethylenecarboxamide, Propenoic acid (amide), propenamide, acrylamide monomer, RCRA waste No. U007, UN 2074, vinyl amide
Acrylamide is a colorless to white crystalline solid. The flake- or leaf-like crystal forms are from the monomer benzene. Unlike benzene it is odorless, however it emits an acrid smell when it decomposes emitting carbon monoxide, carbon dioxide, nitrogen oxides and ammonia. The stability of acrylamide depends on it not being exposed to air, moisture or light. When protected from heat and light, chemical solutions of acrylamide in water, dimethylsulfoxide, 95% ethanol or acetone should be stable for 24 hours.
SOURCES AND MANUFACTURE
1. Until recently all acrylamide in the environment was assumed to be synthetic. The commercial production of acrylamide, a vinyl monomer, began in 1954. Acrylamide forms between 90 and 100 ºC from the hydration of acrylonitrile by sulfuric acid monohydrate creating a sulfate solution. Neutralizing the solution with ammonia extracts acrylamide, which is then cooled to isolate the crystalline monomer. To reduce competition of the by-products polyacrylamide and acrylic acid, copper salts are added to the solution.
The second commercial method known as direct catalytic conversion happens when an aqueous solution of acrylonitril passes over a fixed bed of copper-metal admixtures between 25 and 200 º C.
The main manufactures and importers of acrylamide are:
- American Cyanamid Co. (Wayne, NJ; Avondale, LA; Linden, NJ; Botlek, The Netherlands;
- Dow Chemical USA (Midland, MI)
- Nalco Chemical Co. (Naperville, IL; Garyville, LA)
- BF Goodrich Co. (Cleveland, OH)
- Cosan Chemical Corp. (Carlstadt, NJ)
2. In April 2002, a group of Swedish scientist noted that acrylamide was forming naturally from starchy food cooked at high temperature. More recent studies have shown that the presence of the amino acid, asparagine, and the carbohydrade, glucose form acrylamide at high temperatures. The process is known as caramelisation and can be explained by the Maillard reaction via an Amadori rearrangement and a Strecker degradation reaction where _-dicarbonyls react with an amino acid precursor. This process also takes place with methionine and various carbohydrates. When 20 amino acids were heated individually at 180 C for 30 min only methionine and asparagine produced acrylamide. It has been determined that asparagine creates a 100 fold increase of acrylamide over methionine when heated with glucose. The process is further enhanced when water is added. Acrylamide is produced by various other routes of formation depending on the amino acid precursor. Pyrolysis of methionine, glutamine, cysteine and asparagine with fructose, galactose, lactose or sucrose also leads to acrylamide, while glycosylamines are direct precursors in the pyrolytic reaction.
3. Polyacrylamide breaks down into acrylamide after exposure to light and elevated temperature. Although there are studies that negate these finding or that show the reverse takes place, there are other studies that state that the breakdown continues thereby degrading acrylamide. Often the breakdown takes place on the surface of plant roots, leaves or stems in the soil.
Acrylamide is becoming more abundant in the environment even though it does not bioaccumulate. The amount of acrylamide used in 1987 was 110 million lbs and increased to 120 million lbs in 1992. This does not include its presence in food, which is one of the current issues facing government health agencies.