|Molar mass||126.12 g/mol|
|Melting point||345 °C (653 °F; 618 K) (decomposition)|
|3240 mg/ L (20 °C)|
very slightly soluble in hot alcohol, benzene, glycerol, pyridine
insoluble in ether, benzene, CCl4
Refractive index (nD)
Std enthalpy of
|> 500 °C|
|Lethal dose or concentration (LD, LC):|
LD50 (Median dose)
|3850 mg/kg (rat, oral)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|(: / ?)|
Melamine is an trimer of cyanamide, with a 1,3,5-triazine skeleton. Like cyanamide, it contains 67% nitrogen by mass and, if mixed with resins, has fire retardant properties due to its release of nitrogen gas when burned or charred, and has several other industrial uses. Melamine is also a metabolite of cyromazine, a pesticide. It is formed in the body of mammals that have ingested cyromazine. It has been reported that cyromazine can also be converted to melamine in plants.
Melamine combines with cyanuric acid and related compounds to form melamine cyanurate and related crystal structures, which have been implicated as contaminants or biomarkers in Chinese protein adulterations.
- Etymology 1
- Uses 2
- Acute toxicity 3.1
- Chronic toxicity 3.2
- Treatment of urolithiasis 3.3
- Regulation in food and feed 4
- Synthesis 5
- Production in mainland China 6
Melamine poisoning by tainted food 7
- 2007 Animal feed recalls 7.1
- 2008 Chinese outbreak 7.2
- Testing in food 8
- Detection in biological specimens 9
- Melamine on metal surfaces 10
- See also 11
- References 12
- External links 13
The German word melamin was coined by combining the words: melam (a derivative of ammonium thiocyanate) and amine. Melamine is, therefore, unrelated etymologically to the root melas (μελας, meaning black in Greek), from which the words melanin, a pigment, and melatonin, a hormone, are formed.
Melamine is one of the major components in Pigment Yellow 150, a colorant in inks and plastics.
Melamine also enters the fabrication of melamine poly-sulfonate used as superplasticizer for making high-resistance concrete. Sulfonated melamine formaldehyde (SMF) is a polymer used as cement admixture to reduce the water content in concrete while increasing the fluidity and the workability of the mix during its handling and pouring. It results in concrete with a lower porosity and a higher mechanical strength, exhibiting an improved resistance to aggressive environments and a longer lifetime.
The use of melamine as fertilizer for crops had been envisaged during the 1950s and 1960s because of its high nitrogen content (2/3). However, melamine is much more expensive to produce than are other common nitrogen fertilizers, such as urea. To be effective as a fertilizer, it is essential that the plant nutrients are released or made available in a manner that matches the needs of the growing crop. The nitrogen mineralization process for melamine is extremely slow, making this product both economically and scientifically impractical for use as a fertilizer.
Melamine and its salts are used as fire-retardant additives in paints, plastics, and paper.
Melamine use as non-protein nitrogen (NPN) for cattle was described in a 1958 patent. In 1978, however, a study concluded that melamine "may not be an acceptable non-protein N source for ruminants" because its hydrolysis in cattle is slower and less complete than other nitrogen sources such as cottonseed meal and urea.
Melamine is sometimes illegally added to food products in order to increase the apparent protein content. Standard tests, such as the Kjeldahl and Dumas tests, estimate protein levels by measuring the nitrogen content, so they can be misled by adding nitrogen-rich compounds such as melamine. An instrument (SPRINT) developed by the company CEM Corp allows the determination of protein content directly in some applications; the instrument cannot fooled by adding melamine in the sample
Melamine is also used as a nitrogen and carbon source for N-doped carbon nanotube. N-CNTs can be prepared via Chemical Vapor Deposition (CVD) method by pyrolysizing melamine under an Ar atmosphere in a horizontal glass tube. A thin film of iron (5 nm) is first deposited on a Si/SiO2 wafer. N-CNT synthesis occurs at a furnace temperatures between 800 and 980 °C.
Melamine is described as "Harmful if swallowed, inhaled or absorbed through the skin. Chronic exposure may cause cancer or reproductive damage. Eye, skin and respiratory irritant". However, the short-term lethal dose is on a par with common table salt with an LD50 of more than 3 grams per kilogram of bodyweight. U.S. Food and Drug Administration (FDA) scientists explained that when melamine and cyanuric acid are absorbed into the bloodstream, they concentrate and interact in the urine-filled renal tubules, then crystallize and form large numbers of round, yellow crystals, which in turn block and damage the renal cells that line the tubes, causing the kidneys to malfunction.
The European Union set a standard for acceptable human consumption (
- Melamine Materials Safety Data Sheet (MSDS)
- OECD Screening Information Data Set (SIDS): Melamine (High Production Volume Chemicals Screening Information，PDF, 89 pages).
- FDA Web Page with Information on Pet Food Recall (due to Melamine contamination)
- European Commission decision (2008/798/EC) imposing special conditions governing the import of products containing milk or milk products originating from China
- Statement on melamine from the International Fertilizer Industry Association
- Toxicological and Health Aspects of Melamine and Cyanuric Acid: Report of a WHO Expert Meeting In collaboration with FAO
- Melmac Central's History on Melamine .
- Melamine in the ChemIDplus database
- "Report on cyromazine of the European Medicines Agency" (PDF). Retrieved 2012-06-20.
- Lim, Lori O.; Scherer, Susan J.; Shuler, Kenneth D.; Toth, John P. (1990). "Disposition of cyromazine in plants under environmental conditions". Journal of Agricultural and Food Chemistry 38 (3): 860.
- FAO report on cyromazine
- "Melamine. The American Heritage Dictionary of the English Language: Fourth Edition. 2000.". Retrieved 2008-09-28.
- Bann B., Miller S.A. (1758). "Melamines and derivatives of melamine".
- Hauck, R.D.; H.F. Stephenson (1964). "Nitrification of triazine nitrogen". Fertilizer Nitrogen Sources 12 (2): 147.
- Ashford's Dictionary of Industrial Chemicals, third edition, page 5713
- Barrett, Michael P.; Gilbert, Ian H. (2006). "Advances in Parasitology Volume 63". Advances in Parasitology 63. p. 125.
- "Ruminant feed compositions, Robert W. Colby and Robert J. Mesler Jr., U.S. Patent No. 2819968, 1958
- "Melamine as a dietary nitrogen source for ruminants", G.L.Newton and P.R.Utley, Journal of Animal Science, vol.47, p1338–44, 1978.
- "Protein Pretense", Alison Snyder, Scientific American Magazine, August 2008
- Moore, Jeffrey C.; Devries, Jonathan W.; Lipp, Markus; Griffiths, James C.; Abernethy, Darrell R. (2010). "Total Protein Methods and Their Potential Utility to Reduce the Risk of Food Protein Adulteration". Comprehensive Reviews in Food Science and Food Safety 9 (4): 330.
- Synthesis of high nitrogen doping of carbon nanotubes and modeling the stabilization of filled DAATO@ CNTs (10, 10) for nanoenergetic materials
- "Melamine in milk by David Bradley". Sciencebase. 17 September 2008. Retrieved 2008-09-27.
- Weise, Elizabeth (5 August 2007). "Poison pet food woes seem to hit cats harder". USA Today. Retrieved 2008-10-01.
- Rory Harrington (15 April 2010). "EFSA cuts melamine TDI by 60 per cent". FoodQualityNews.com. Retrieved 2010-04-16.
- Lara Endreszl (10 December 2008). "Safe Melamine Levels Named by World Health Organization". Health News.
- Neergaard, Lauran. "Study Examines Why Most Survived China’s Melamine Scare". Food Manufacturing News. Food Manufacturing. Retrieved 22 February 2013.
- Zheng, X (13 Feb 2013). "Melamine-induced renal toxicity is mediated by the gut microbiota". Science Translational Medicine 5 (172).
- "Flame Retardants Center: Melamine Compounds". Specialchem4polymers.com. 2010-04-19. Retrieved 2012-06-20.
- A.A. Babayan, A.V.Aleksandryan, "Toxicological characteristics of melamine cyanurate, melamine and cyanuric acid", Zhurnal Eksperimental'noi i Klinicheskoi Meditsiny, Vol.25, 345–9 (1985). Original article in Russian, English abstract retrieved from SciFinder on either 2007-07-05 or 2007-05-07.
- Puschner, B.; Poppenga, R. H.; Lowenstine, L. J.; Filigenzi, M. S.; Pesavento, P. A. (2007). "Assessment of Melamine and Cyanuric Acid Toxicity in Cats". Journal of Veterinary Diagnostic Investigation 19 (6): 616–24.
- Dobson, R. L. M.; Motlagh, S.; Quijano, M.; Cambron, R. T.; Baker, T. R.; Pullen, A. M.; Regg, B. T.; Bigalow-Kern, A. S.; Vennard, T.; Fix, A.; Reimschuessel, R.; Overmann, G.; Shan, Y.; Daston, G. P. (2008). "Identification and Characterization of Toxicity of Contaminants in Pet Food Leading to an Outbreak of Renal Toxicity in Cats and Dogs". Toxicological Sciences 106 (1): 251–62.
- Zhang, Xiangbo; Bai, Jinliang; Ma, Pengcheng; Ma, Jianhua; Wan, Jianghou; Jiang, Bin (2010). "Melamine-induced infant urinary calculi: A report on 24 cases and a 1-year follow-up". Urological Research 38 (5): 391–5.
- "International Chemical Safety Card". Cdc.gov. Retrieved 2012-06-20.
- OSHA – Chemical sampling information
- WHO – Some Chemicals that Cause Tumors of the Kidney or Urinary Bladder in Rodents and Some Other Substances
- Heck, Henry d'A.; Tyl, Rochelle W. (1985). "The induction of bladder stones by terephthalic acid, dimethyl terephthalate, and melamine (2,4,6-triamino-s-triazine) and its relevance to risk assessment". Regulatory Toxicology and Pharmacology 5 (3): 294–313.
- T.W. Tusing, "Chronic Feeding – Dogs", cited by "Summary of toxicity data – trichloromelamine" by California Environmental Protection Agency, last revised on 04-02-2002, URL accessed on 05-09-2007
- "Culprit in pet food deaths may be combination of contaminants".
- "Proceedings of the American Association of Veterinarian Laboratory Diagnosticians 50th Annual Conference" (PDF).
- "Researchers examine contaminants in food, deaths of pets".
- "International experts limit melamine levels in food".
- Kirk-Othmer encyclopedia of chemical technology, 3rd edition, Vol.7, p303–304, 1978.
- Lahalih, Shawqui M.; Absi-Halabi, M. (1989). "Recovery of solids from melamine waste effluents and their conversion to useful products". Industrial & Engineering Chemistry Research 28 (4): 500.
- "How a golden chemical became greeneer", Nitrogen+Syngas, Issue 293, May–June 2008.
- Ruilin, Wang (6 January 2006). "Melamine capacity is serious surplus". China Chemical Reporter. Retrieved 2007-04-21.
- "Tainted milk trial opens in China". British Broadcasting Corporation. December 26, 2008. Retrieved January 7, 2009.
- "Chinese Milk Scam Duo Face Death". British Broadcasting Corporation. January 22, 2009. Retrieved January 22, 2009.
- CNN: Dry food added to pet food recall list
- "Pet food recall". AVMA. Retrieved 2012-06-20.
- Press release by Natural Balance Pet Foods
- "FDA: Pet food recall". Fda.gov. Retrieved 2012-06-20.
- David Barboza and Alexei Barrionuevo (30 April 2007). "Filler in Animal Feed Is Open Secret in China". The New York Times. Retrieved 2007-04-30.
- David Barboza and Alexei Barrionuevo (3 May 2007). "China Makes Arrest in Pet Food Case". The New York Times. Retrieved 2007-05-03.
- "Products". Shandong Mingshui Great Chemical Group. Archived from the original on July 26, 2005. Retrieved 2007-04-30.
- Andrew Martin (31 May 2007). "Poison used in China is found in U.S.-made animal feed". The New York Times. Retrieved 2007-06-01.
- Scott McDonald, "Nearly 53,000 Chinese children sick from milk", Associated Press (22 September 2008)
- Jane Macartney, China baby milk scandal spreads as sick toll rises to 13,000, The Times (September 22, 2008)
- "Toxicological and Health Aspects of Melamine and Cyanuric Acid" (PDF).
- Guan, Na; Fan, Qingfeng; Ding, Jie; Zhao, Yiming; Lu, Jingqiao; Ai, Yi; Xu, Guobin; Zhu, Sainan; Yao, Chen; Jiang, Lina; Miao, Jing; Zhang, Han; Zhao, Dan; Liu, Xiaoyu; Yao, Yong (2009). "Melamine-Contaminated Powdered Formula and Urolithiasis in Young Children". New England Journal of Medicine 360 (11): 1067–74.
- "Fonterra says somebody sabotaged milk". NZ Herald. September 15, 2008. Retrieved 2008-09-22.
- "Toxic milk toll rockets in China". BBC NEWS. September 15, 2008. Retrieved 2008-09-22.
- Tran, Tini (September 17, 2008). "6,200 Chinese babies ill, 3 die from tainted milk". Yahoo! News. Retrieved 2008-09-22.
- "Hong Kong widens China food tests". BBC News. 27 October 2008. Retrieved 2008-10-27.
- Pliny (2010-07-09). "Melamine tainted milk re-emerges in northwest China plant".
- Michael Wines (July 9, 2010). "Tainted Dairy Products Seized in Western China".
- Langman, Craig B. (2009). "Melamine, Powdered Milk, and Nephrolithiasis in Chinese Infants". New England Journal of Medicine 360 (11): 1139–41.
- "Diagnosis and treatment of melamine-associated urinary calculus complicated with acute renal failure in infants and young children". Chinese Medical Journal 122 (3): 245–51. 2009.
- Li, Gang; Jiao, Shufang; Yin, Xiangjun; Deng, Ying; Pang, Xinghuo; Wang, Yan (2009). "The risk of melamine-induced nephrolithiasis in young children starts at a lower intake level than recommended by the WHO". Pediatric Nephrology 25 (1): 135–41.
- Liu, J.-m.; Ren, A.; Yang, L.; Gao, J.; Pei, L.; Ye, R.; Qu, Q.; Zheng, X. (2010). "Urinary tract abnormalities in Chinese rural children who consumed melamine-contaminated dairy products: A population-based screening and follow-up study". Canadian Medical Association Journal 182 (5): 439–43.
- "About melamine". Irmm.jrc.ec.europa.eu. 2012-02-02. Retrieved 2012-06-20.
- Breidbach, A., Bouten, K., Kroger, K., Ulberth, F. "Melamine Proficiency Test 2009"
- U.S. FDA Laboratory Information Bulletin No 4421 – http://www.cfsan.fda.gov/~frf/lib4421.html
- Japanese Ministry of Health, Labor and Welfare – http://www.forth.go.jp/keneki/kanku/syokuhin/tsuuchi/2008/10/3_1.pdf
- Zwitterionic HILIC separation of melamine and cyanuric acid – http://www.sequant.com/melamine
- Hodge, James (2008-12-12). "Dairy detection: monitoring melamine in milk". Chemical Science (Royal Chemical Society, RCS Publishing) (02). Retrieved 2009-01-04.
- Zhu, Liang; Gamez, Gerardo; Chen, Huanwen; Chingin, Konstantin; Zenobi, Renato (2009). "Rapid detection of melamine in untreated milk and wheat gluten by ultrasound-assisted extractive electrospray ionization mass spectrometry (EESI-MS)". Chemical Communications (5): 559.
- Huang, Guangming; Ouyang, Zheng; Cooks, R. Graham (2009). "High-throughput trace melamine analysis in complex mixtures". Chemical Communications (5): 556.
- McKenna, Phil (2009-01-07). "Rise of the garage genome hackers". New Scientist. Retrieved 2009-02-17.
- Marcus, Wohlsen (2008-12-26). "Amateurs are trying genetic engineering at home". Copyright 2008 The Associated Press. Retrieved 2009-02-17.
- Ishiwata H, Inoue T, Yamazaki T, Yoshihira K (1987). "Liquid chromatographic determination of melamine in beverages". J Assoc off Anal Chem 70 (3): 457–60.
- Sancho, J.V.; Ibáñez, M.; Grimalt, S.; Pozo, Ó.J.; Hernández, F. (2005). "Residue determination of cyromazine and its metabolite melamine in chard samples by ion-pair liquid chromatography coupled to electrospray tandem mass spectrometry". Analytica Chimica Acta 530 (2): 237.
- "Cyromazine and Melamine" (PDF).
- "Chemistry Laboratory Guidebook".
- "HPLC Determination of Melamine, Ammeline, Ammelide, and Cyanuric Acid Contamination in Wheat Gluten and Rice Protein Concentrate".
- He, Lili; Liu, Yang; Lin, Mengshi; Awika, Joseph; Ledoux, David R.; Li, Hao; Mustapha, Azlin (2008). "A new approach to measure melamine, cyanuric acid, and melamine cyanurate using surface enhanced Raman spectroscopy coupled with gold nanosubstrates". Sensing and Instrumentation for Food Quality and Safety 2: 66.
- Lin, M.; He, L.; Awika, J.; Yang, L.; Ledoux, D.R.; Li, H.; Mustapha, A. (2008). "Detection of Melamine in Gluten, Chicken Feed, and Processed Foods Using Surface Enhanced Raman Spectroscopy and HPLC". Journal of Food Science 73 (8): T129.
- European Commission decision (2008/798/EC) imposing special conditions governing the import of products containing milk or milk products originating from China
- Baselt RC (2014). Disposition of toxic drugs and chemicals in man. Seal Beach, Ca.: Biomedical Publications. pp. 1213–1214.
- Silly, F.; Q. Shaw, A.; et.al. (2008). "Melamine Structures on the Au(111) Surface". J. Phys. Chem. C 112: 11476.
- H. Schmitz, C.; Ikonomov, J.; Sokolowski. M (2011). "Two commensurate hydrogen-bonded monolayer structures of melamine on Ag(111)". Surface Science 605: 1.
- Šimėnas, M.; Tornau, E. E. (2014). "A model of melamine molecules ordering on metal surfaces". J. Chem. Phys. 141: 054701.
- Mura, M.; Martsinovich, N.; Kantorovich, L. (2008). "Theoretical study of melamine superstructures and their interaction with the Au(111) surface". Nanotechnology 19: 465704.
It is reported that melamine molecules adsorbed on Au(111) or Ag(111) surface tend to arrange into honeycomb or closed-packed structures. Such a self-assembly occurs due to the inter-molecular hydrogen bond interaction. This ordering was further investigated using classical Monte Carlo and DFT methods.
Melamine on metal surfaces
Melamine has been determined in urine specimens from children who consumed adulterated milk products by liquid chromatography-mass spectrometry.
Detection in biological specimens
Member States of the European Union are required under Commission Decision 2008/757/EC to ensure that all composite products containing at least 15% of milk product, originating from China, are systematically tested before import into the Community and that all such products which are shown to contain melamine in excess of 2.5 mg/kg are immediately destroyed.
The Food Safety and Inspection Service (FSIS) of the United States Department of Agriculture (USDA) provides a test method for analyzing cyromazine and melamine in animal tissues. In 2007, the FDA began using a high performance liquid chromatography test to determine the melamine, ammeline, ammelide, and cyanuric acid contamination in food. another procedure is based on surface-enhanced Raman spectroscopy (SERS).
Because melamine resin is often used in food packaging and tableware, melamine at ppm level (1 part per million) in food and beverage has been reported due to migration from melamine-containing resins. Small amounts of melamine have also been reported in foodstuff as a metabolite product of cyromazine, an insecticide used on animals and crops.
The Melaminometer was a hypothetical design for a synthetic biology circuit, to used for detecting melamine and related chemical analogues such as cyanuric acid. The conceptual project is hosted at OpenWetWare as open source biology in collaboration with DIYbio and has been discussed in various newspapers in the context of homebrew biotechnology. As of October 2009, the design has not been verified.
Huang et al., (2008) have also developed at Purdue University (US) a simpler instrumentation and a faster method by using a low-temperature plasma probe to ionize the samples. The major obstacles being solved, the ESI-MS technique allows now high-throughput analysis of melamine traces in complex mixtures.
Ultrasound-assisted extractive electrospray ionization mass spectrometry (EESI-MS) has been developed at ETH Zurich (Switzerland) by Zhu et al., (2008) for a rapid detection of melamine in untreated food samples. Ultrasounds are used to nebulize the melamine-containing liquids into a fine spray. The spray is then ionised by extractive electrospray ionisation (EESI) and analysed using tandem mass spectrometry (MS/MS). An analysis requires 30 seconds per sample. The limit of detection of melamine is a few nanograms of melamine per gram of milk.
The existing methods for melamine determination using a triple quadrupole liquid chromatography – mass spectrometry (LC/MS) after solid phase extraction (SPE) are often complex and time consuming. However, electrospray ionization methods coupled with mass spectrometry allow a rapid and direct analysis of samples with complex matrices: the native liquid samples are directly ionized under ambient conditions in their original solution. In December 2008, two new fast and inexpensive methods for detecting melamine in liquids have been published on-line in the Chem. Comm. Journal of the Royal Society of Chemistry (UK).
In October 2008, the U.S. Food and Drug Administration (FDA) issued new methods for the analysis of melamine and cyanuric acid in infant formulations in the Laboratory Information Bulletin No 4421. Similar recommendations have been issued by other authorities, like the Japanese Ministry of Health, Labor and Welfare, both based on liquid chromatography – mass spectrometry (LC/MS) detection after hydrophilic interaction liquid chromatography (HILIC) separation.
Following the deaths of children in China from powdered milk in 2008, the Joint Research Centre (JRC) of the European Commission in Belgium set up a website about methods to detect melamine. In May 2009, the JRC published the results of a study that benchmarked the ability of labs around the world to accurately measure melamine in food. The study concluded that the majority of labs can effectively detect melamine in food.
Until the 2007 pet food recalls, melamine had not routinely been monitored in food, except in the context of plastic safety or insecticide residue. This could be due to the previously assumed low toxicity of melamine, and the relatively expensive methods of detection.
Testing in food
In a study published in 2010, researchers from Beijing University studying ultrasound images of infants who fell ill in the 2008 contamination found that while most children in a rural Chinese area recovered, 12 per cent still showed kidney abnormalities six months later. "The potential for long-term complications after exposure to melamine remains a serious concern," the report said. "Our results suggest a need for further follow-up of affected children to evaluate the possible long-term impact on health, including renal function." Another 2010 follow-up study from Lanzhou University attributed the uric acid stone accumulation after ingestion of melamine to a rapid aggradation of metabolites such as cyanuric acid diamide (ammeline) and cyanuric acid and reported that urine alkalinization and stone liberalization were the most effective treatments.
 In a 2009 study of 683 children diagnosed in Beijing in 2008 with
Urinary calculi specimens were collected from 15 cases treated in Beijing and were analyzed as unknown objects for their components at Beijing Institute of Microchemistry using infrared spectroscopy, nuclear magnetic resonance, and high performance liquid chromatography. The result of the analysis showed that the calculus was composed of melamine and uric acid, and the molecular ratio of uric acid to melamine was around 2:1.
On characterization and treatment of urinary stones in affected infants, the New England Journal of Medicine printed an editorial in March 2009, along with reports on cases from Beijing, Hong Kong and Taipei.
As of July 2010, Chinese authorities were still reporting some seizures of melamine-contaminated dairy product in some provinces, though it was unclear whether these new contaminations constituted wholly new adulterations or were the result of illegal reuse of material from the 2008 adulterations.
In October 2008, "Select Fresh Brown Eggs" imported to Hong Kong from the Hanwei Group in Dalian in northeastern China, were found to be contaminated with nearly twice the legal limit of melamine. York Chow, the health secretary of Hong Kong, said he thought animal feeds might be the source of the contamination and announced that the Hong Kong Centre for Food Safety would henceforward be testing all mainland Chinese pork, farmed fish, animal feed, chicken meat, eggs, and offal products for melamine.
In September 2008, several companies, including Nestlé, were implicated in a scandal involving milk and infant formula which had been adulterated with melamine, leading to kidney stones and other renal failure, especially among young children. By December 2008, nearly 300,000 people had become ill, with more than 50,000 infant hospitalizations and six infant deaths. In a study published in the New England Journal of Medicine, it was reported that melamine exposure increased the incidence of urinary tract stones by seven times in children. Melamine may have been added to fool government protein content tests after water was added to fraudulently dilute the milk. Because of melamine's high nitrogen content (66% by mass versus approx. 10–12% for typical protein), it can cause the protein content of food to appear higher than the true value. Officials estimate that about 20 percent of the dairy companies tested in China sell products tainted with melamine. On January 22, 2009, three of those involved in the scandal (including one conditional sentence) were sentenced to death in a Chinese court.
2008 Chinese outbreak
Another recall incident in 2007 involved melamine which had been purposely added as a binder to fish and livestock feed manufactured in the United States. This was traced to suppliers in Ohio and Colorado.
In April 2007, The New York Times reported that the addition of "melamine scrap" into fish and livestock feed to give the false appearance of a higher level of protein was an "open secret" in many parts of mainland China, reporting that this melamine scrap was being produced by at least one plant processing coal into melamine. Four days later, the New York Times reported that, despite the widely reported ban on melamine use in vegetable proteins in mainland China, at least some chemical manufacturers continued to report selling it for use in animal feed and in products for human consumption. Li Xiuping, a manager at Henan Xinxiang Huaxing Chemical in Henan Province, stated, "Our chemical products are mostly used for additives, not for animal feed. Melamine is mainly used in the chemical industry, but it can also be used in making cakes." Shandong Mingshui Great Chemical Group, the company reported by the New York Times as producing melamine from coal, produces and sells both urea and melamine but does not list melamine resin as a product.
In 2007, a pet food recall was initiated by Menu Foods and other pet food manufacturers who had found their products had been contaminated and caused serious illnesses or deaths in some of the animals that had eaten them. In March 2007, the US Food and Drug Administration reported finding white granular melamine in the pet food, in samples of white granular wheat gluten imported from a single source in China, Xuzhou Anying Biologic Technology as well as in crystalline form in the kidneys and in urine of affected animals. Further vegetable protein imported from China was later implicated.
2007 Animal feed recalls
Melamine has been involved in several food recalls after the discovery of severe kidney damage to children and pets poisoned by melamine-adulterated food.
Melamine poisoning by tainted food
Surplus melamine has been an adulterant for feedstock and milk in mainland China for several years now because it can make diluted or poor quality material appear to be higher in protein content by elevating the total nitrogen content detected by some simple protein tests. Actions taken in 2008 by the Government of China have reduced the practice of adulteration, with the goal of eliminating it. Court trials began in December 2008 for six people linked to the scandal and ended in January 2009 with two of the convicts being sentenced to death and executed.
Between the late 1990s and early 2000s, both consumption and production of melamine grew considerably in mainland China. By early 2006, melamine production in mainland China is reported to be in "serious surplus". Between 2002 and 2007, while the global melamine price remained stable, a steep increase in the price of urea (feedstock for melamine) has reduced the profitability of melamine manufacturing. Currently, China is the world's largest exporter of melamine, while its domestic consumption still grows by 10% per year. However, reduced profit has already caused other joint melamine ventures to be postponed there.
Production in mainland China
Crystallization and washing of melamine generates a considerable amount of waste water, which is a pollutant if discharged directly into the environment. The waste water may be concentrated into a solid (1.5–5% of the weight) for easier disposal. The solid may contain approximately 70% melamine, 23% oxytriazines (ammeline, ammelide, and cyanuric acid), 0.7% polycondensates (melem, melam, and melon). In the Eurotecnica process, however, there is no solid waste and the contaminants are decomposed to ammonia and carbon dioxide and sent as off gas to the upstream urea plant; accordingly, the waste water can be recycled to the melamine plant itself or used as clean cooling water make-up.
The off-gas contains large amounts of ammonia. Therefore, melamine production is often integrated into urea production, which uses ammonia as feedstock.
The above reaction can be carried out by either of two methods: catalyzed gas-phase production or high pressure liquid-phase production. In one method, molten urea is introduced onto a fluidized bed with catalyst for reaction. Hot ammonia gas is also present to fluidize the bed and inhibit deammonization. The effluent then is cooled. Ammonia and carbon dioxide in the off-gas are separated from the melamine-containing slurry. The slurry is further concentrated and crystallized to yield melamine. Major manufacturers and licensors such as Orascom Construction Industries, BASF, and Eurotecnica have developed some proprietary methods.
The second reaction is exothermic but the overall process is endothermic.
- 6 HCNO + 3 NH3 → C3H6N6 + 3 CO2 + 3NH3
Then, cyanic acid polymerizes to form cyanuric acid which condenses with the liberated ammonia forming melamine which releases water which then reacts with cyanic acid present(which helps to drive the reaction) generating carbon dioxide and ammonia.
- (NH2)2CO → HCNO + NH3
It can be understood as two steps.
- 6 (NH2)2CO → C3H6N6 + 6 NH3 + 3 CO2
Melamine was first synthesized by the German chemist Justus von Liebig in 1834. In early production, first calcium cyanamide is converted into dicyandiamide, then heated above its melting temperature to produce melamine. However, today most industrial manufacturers use urea in the following reaction to produce melamine:
The United Nations' food standards body, Codex Alimentarius Commission, has set the maximum amount of melamine allowed in powdered infant formula to 1 mg/kg and the amount of the chemical allowed in other foods and animal feed to 2.5 mg/kg. While not legally binding, the levels allow countries to ban importation of products with excessive levels of melamine.
Regulation in food and feed
Fast diagnosis and treatment of acute obstructive urolithiasis may prevent the development of acute renal failure. Urine alkalinization and stone liberalization have been reported to be the most effective treatments in humans.
Treatment of urolithiasis
A survey commissioned by the American Association of Veterinary Laboratory Diagnosticians suggested that crystals formed in the kidneys when melamine combined with cyanuric acid, "don't dissolve easily. They go away slowly, if at all, so there is the potential for chronic toxicity."
A study in 1953 reported that dogs fed 3% melamine for a year had the following changes in their urine: (1) reduced specific gravity, (2) increased output, (3) melamine crystalluria, and (4) protein and occult blood.
A toxicology study in animals conducted after recalls of contaminated pet food concluded that the combination of melamine and cyanuric acid in diet does lead to acute renal failure in cats. A 2008 study produced similar experimental results in rats and characterized the melamine and cyanuric acid in contaminated pet food from the 2007 outbreak. A 2010 study from Lanzhou University attributed renal failure in humans to uric acid stone accumulation after ingestion of melamine resulting in a rapid aggregation of metabolites such as cyanuric acid diamide (ammeline) and cyanuric acid.
Melamine is reported to have an oral LD50 of 3248 mg/kg based on rat data. It is also an irritant when inhaled or in contact with the skin or eyes. The reported dermal LD50 is >1000 mg/kg for rabbits. A study by USSR researchers in the 1980s suggested that melamine cyanurate, commonly used as a fire retardant, could be more toxic than either melamine or cyanuric acid alone. For rats and mice, the reported LD50 for melamine cyanurate was 4.1 g/kg (given inside the stomach) and 3.5 g/kg (via inhalation), compared to 6.0 and 4.3 g/kg for melamine and 7.7 and 3.4 g/kg for cyanuric acid, respectively.
Toxicity of melamine can be mediated by intestinal microbes. In culture, Klebsiella terrigena, which rarely colonizes mammalian intestines, was shown to convert melamine to cyanuric acid directly. Rats colonized by K. terrigena showed greater melamine-induced kidney damage compared to those not colonized.