.png)
Milk powder in a Shanghai supermarket. (AFP/Getty Images)
China’s recent poisonous milk scandal which led to the death of at least four infants has made people familiar with the dangers of melamine consumption.
Melamine as an important chemical raw material is extensively used in timber processing, plastic, coatings, papermaking, adhesive, textile, leather, electric, pharmaceutical, flame-retarding agent and rubber antioxidant sectors. The rapid development of reinforced composite floorings in China in recent years, especially in its domestic construction industry, has led to a rapid growth of the melamine consumption.
Currently, China is the world’s largest producer and exporter of melamine, while its domestic melamine consumption is growing by around 10 percent per year, according to DMS’s melamine industry update on June 2007.
The Alibaba Chemical Web site (chem.china.alibaba.com) said that in 2007 China’s melamine production capacity was more than 600,000 tons a year, and actual output of melamine about 400,000 tons a year.
Ongoing growth in domestic demand, combined with lower production capabilities has resulted in a very tight melamine supply and demand in China since the fourth quarter in 2007, according to DMS’s melamine industry update on March 2008.
China Chemical Network (china.chemnet.com) has listed melamine’s wholesale price between 11,000 and 11,800 yuan (US$1,614 to $1,731) a ton, as of May 31. The higher end exceeded 12,000 yuan ($1,761). Even products with a lower purity that are extracted from crude materials by small companies sell for 8,000 yuan ($1,174) per ton.
Based on melamine’s current price, adding it into animal feed or raw milk seems to be uneconomical.
Nontoxic Nitrogen-Rich Chemical
Melamine is a basic organic chemical intermediate, with chemical formula C3H6N6. It is commonly produced from urea, and contains 66 percent nitrogen by mass.
Nitrogen is a very important building stone of all living beings. The element is an essential ingredient of proteins, which make up most of the human body that isn’t bone or water. As such, making nitrogen measurement is a common practice for protein content estimation. The Kjeldahl and Dumas testing methods are the standard tests used in the food industry for measuring total nitrogen in crude protein content while they can be misguided by adding nitrogen-rich compounds such as melamine.
Melamine use as non-protein nitrogen (NPN) to feed cattle was issued in a U.S. patent in 1958. The patent lasted 20 years and was later banned due to inefficiency as a NPN source for ruminant.
In China’s melamine-tainted milk scandal, melamine as a nitrogen-rich substance is illegally added to baby formula in order to increase the apparent protein content and pass the quality tests, though the chemical has no nutritional value.
So how has melamine gotten into the baby formula? Nobody knows thus far.
But one fact is that melamine is only slightly soluble in water, it, when is being illegally added into milk products, will be dissolved in formaldehyde (carcinogen) or other organic solvents before mixing into the milk. Experts doubt that dairy farmers, who were blamed for the tainted milk scandal, would know such complicate chemical compound technique.
In addition, melamine by itself is non-toxic in low doses. However, when melamine combines with cyanuric acid in water or diet to form melamine cyanurate, it will lead to fatal kidney stones or renal problems.
According to David Bradley’s article posted on Sciencebase.com on Sep. 17, 2008, melamine is described as being “Harmful if swallowed, inhaled or absorbed through the skin. Chronic exposure may cause cancer or reproductive damage. Eye, skin and respiratory irritant.” However, the toxic dose is on a par with common table salt with an LD50 of more than 3 grams per kilogram of bodyweight, he added.
He says, “But, if melamine has low toxicity then what is it that has poisoned thousands of babies in China and why has this scandal occurred? Well, LD50, the toxic dose issue, tells us something about acute exposure not the apparent six-month’s worth of accumulated exposure these babies have suffered. Chronic exposure to melamine can lead to bladder or kidney stones and even bladder cancer and as we have learned, acute kidney failure.”
In the end, he points out the fact—that has been ignored by melamine-contaminated milk headlines—melamine added to the milk may not be pure.
Melamine Scrap
Melamine scrap, small acorn-sized chunks of white rock, is a by-product from processing of coal into melamine. It has been reported by New York Times on 30 April 2007, following China’s melamine-tainted pet food scandal last year, that melamine scrap is widely incorporated into livestock and fish feed in parts of China.
According to the report, nitrogen-rich melamine scrap is routinely ground into powder and mixed into low-grade wheat, corn, soybean or other proteins to inflate the protein analysis of animal feed. Such melamine powder has been called “fake protein” and is used to deceive animal farmers into thinking they are buying feed that provides higher nutrition value.
The practice is widespread in China. For years many animal feed sellers have been able to cheat buyers by blending a powdered form of the scrap into feed with little regulatory supervision, according to interviews with melamine scrap traders and agricultural workers here, described in the report.
The resulting melamine-tainted feed would be weak in protein but, by using melamine additive, the feed seller makes a huge profit because melamine scrap is much cheaper than soy, wheat or corn protein.
The report quoted a manager named Guo Qingyin as saying, “In the past melamine scrap was free, but the price has been going up in the past few years. Consumption of melamine scrap is probably bigger than that of urea in the animal feed industry now.”
A chemical industry insider from Puyang City in Henan Province said in an interview with Caijing Magazine that he was aware of some company that had produced a batch of melamine scrap almost every two to three months.
“It is possible that melamine is added into soybean meal, a cheap source of protein products, or other milk additives before dairy producers buy, or it is adulterated by the milk powder manufacturers themselves,” said the insider.
The price for such waste melamine is often very low, and before 2005 it was almost given away for free. The price has risen now, but it is still sold for only as high as 700 to 800 yuan ($103 to $117) per ton. However as soon as they are packaged as “protein essence” to be sold on the market, their price can jump to as high as 4,000 yuan ($587) a ton.
If the melamine contained in the milk powder or liquid milk comes from adding melamine scrap, there will be more ingredients to be worried about.
A reporter in Caijing learned that as an impure form of the chemical, such leftover melamine scrap often contains urea, ammonia, silica, potassium nitrate, sodium nitrite, acetic acid, and activated carbon. Sodium nitrite is also internationally recognized as a carcinogen.
According to China’s State Administration of Quality Supervision, Inspection and Quarantine (SAQSIQ), the content of melamine in Sanlu baby milk powder products is as high as 2,563 milligrams per kilogram. Some industry insiders said that the high concentration of melamine in some brands of milk powder could be linked to hidden operating rules for milk powder manufacturers.
