The Suggestions Of Preventive Measures

Published Date: 02 Nov 2017

The 2008 Chinese milk scandal was the biggest food crisis that occurred in the People’s Republic of China where milk suppliers were artificially adding melamine into dairy products to enhance diluted protein content in dairy products by increasing the nitrogen content. Melamine-tainted dairy products caused acute kidney failure and death in babies and animals which had also affected other countries where the products were exported to (Zhao, L., Lim, T.S., 2008). This scandal was a result of strong competition amongst Chinese milk companies and poor quality control system by the local authorities which led to the adulteration of protein-based products to lower production cost. Mitigation efforts were slow as the companies and local government were trying to cover up the incident in December 2007. The tainted products were only recalled globally in September 2008 (Zhao, L., Lim, T.S., 2008). This had further affected derivative milk products to be tainted by melamine such as ice cream, yoghurt, candies and pet food ingredients. Eggs were also found to be tainted from mixing melamine into chicken feed to enhance the protein content (BBC, 2008). The main dairy company involved Sanlu Group, had filed for bankruptcy in December 2008. In 2009, two people were executed while nineteen others were sentenced to prison terms for involving in this scandal (BBC, 2009).

Information on Substances

Melamine is a fine, white, solid crystalline compound (Jia, X., et.al, 2012) used to make plastics, fertilizers, glues and adhesives, and concrete (BBC, 2010) (Tolleson, W.H., et.al, 2009). The IUPAC name is 1,3,5-triazine-2,4,6-triamine with chemical formula of C3H6N6. It has a molecular weight of 126.12 g/mole and density of 1574 kg/m3. It is composed of high 66.6% nitrogen by weight with melting point of 345 – 347ºC. Melamine is produced commercially using urea as the initial material and is not approved for use in food in the USA (Tolleson, W.H., et.al, 2009). However it may enter the food chain through trace levels present in the environment such as continual use of melamine plastic ware or indirectly from melamine-tainted animal feeds such as fertilizers (Hilts, C., Pelletier, L., 2009). Refer Appendix A for material safety datasheet (MSDS) and the chemical structure of melamine.

Mass and/or Heat Transfer

A mass and/or heat transfer study (Battaglia, M., et.al, 2010) has been done by evaluating the excretion pattern of melamine from feed to milk and the subsequent transfer to cheese and whey. This was done after a single oral dose from the source. The transmission of cyanuric acid was also examined. Twenty four lactating Holstein cows were randomly selected to 4 treatments and received single doses of melamine as follows from 0.05 to 50.00 g/cow for groups D1, D2, D3, and D4, respectively. Each milk sample was collected for melamine and cyanuric acid analyses from days 1 to 7. The individual milk collection from the second milking after melamine consumption was used to make cheese for laboratory testing. Melamine and cyanuric acid were distilled and liquid chromatography-mass spectrometry/mass spectrometry analyses were carried out. The highest melamine concentrations occurred between 6 and 18 hours after treatment and increased with log dose (linear and quadratic), ranging from 0.019 to 35.105 mg/kg. More than 60% of the melamine that was transferred to the milk was observed within 30 hours after melamine ingestion. After 5 days, melamine was not detected in milk after treatment in group D1, and after 7 days after treatment in groups D2, D3, and D4. Blood urea nitrogen was not influenced by melamine ingestion. During cheese making, melamine was transferred mainly to the whey fraction. Cyanuric acid was not detected in any of the samples (milk, cheese, or whey). The excretion pattern of melamine in milk and whey may represent a health concern when cows ingest more than 0.50 g of melamine/day. The limits as set by the European Union can exceed at intake levels of 5 and 50 g/day. This demonstrates that mass and/or heat transfer of melamine via adulteration of animal feeds can affect the contamination in milk and its derivatives.

Chemical Reaction

Melamine is an organic compound. It was first synthesized by German chemist Justus von Liebig in 1834. In the beginning year of production, melamine is produced by converting calcium cyanamide into dicyandiamide, and then heated above its melting temperature. However, most industrial manufacturers nowadays use urea in the following reaction to produce melamine (Mohamed Zakeel, M.C., 2008).

6 (NH2)2CO → C3H6N6 + 6 NH3 + 3 CO2

There are two steps taking place in the reaction. First, the urea will decompose into cyanic acid and ammonia in an endothermic reaction. Subsequently, cyanic acid will polymerize to form melamine and carbon dioxide in exothermic reaction. Overall process is endothermic whereby energy is absorbed in the form of heat (Low, C.K., 2008).

First Step: (NH2)2CO → HCNO + NH3

Second Step: 6 HCNO → C3H6N6 + 3 CO2

The reaction can be carried out by either using catalyzed gas-phase production or high pressure liquid production method. Off-gas products containing ammonia and carbon dioxide are separated from melamine-containing slurry. The slurry further concentrated and crystallized to produce melamine (Mohamed Zakeel, M.C., 2008).

Melamine does not pose a risk in low doses. However in combination with cyanuric acid, it can form insoluble crystals which lead to the formation of kidney stones (Britt, E.E., 2008). Figure 2 in Appendix B shows the formula of combination melamine-cyanuric acid complex.

Toxicity

Melamine is an industrial chemical used as a flame retardant and plastic stabilizer. It is described as being harmful if swallowed, inhaled or absorbed through the skin. Toxicity of melamine can be moderated by intestinal microbes. When melamine and cyanuric acid are absorbed into the bloodstream, they concentrate and interact in the urine-filled renal microtubules, 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 (Weise, E., 2007).

Chronic toxicity

Ingestion of melamine may lead to reproductive damage, or bladder or kidney stones, which can lead to bladder cancer. Chronic exposure may cause cancer, reproductive damage and eye, skin and respiratory irritant. The short term lethal dose is equivalent to common table salt with LD50 of more than 3 g/kg of bodyweight (Bradley, D., 2008).

Acute toxicity

Melamine has 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 above 1000 mg/kg for rabbits. A 2010 study from Lanzhou University linked renal failure in humans to uric acid stone accumulation after ingestion of melamine causing a rapid aggregation of metabolites such as cyanuric acid diamide (ammeline) and cyanuric acid (Zhang, X., et.al, 2010).

China milk scandal toxicology findings

In China, only a fraction of the children who ingested the tainted milk products actually got sick. There were doubts that melamine is the only cause of the poisoning. Scientists believe that it had associations not within the adulterated milk but in the bodies of the victims themselves, specifically the bacteria residing in their intestines. Initial tests of tainted milk failed to find cyanuric acid, however it may have still played a role in the 2008 poisoning. Cyanuric acid can also be synthesized from melamine and the transformation can be achieved by certain bacteria that produce cyanuric acid as a byproduct of melamine metabolism (Reshanov, A., 2013).

Suggestions of Preventive Measures (Shah)

Legislation/Regulation/etc (Shah)