Melamine - the nitty-gritty (FAQs)

What is melamine?

Chemical structure of melamine 

Melamine (1,3,5-triazine-2,4,6-triamine) is a commercial organic basic constructed from urea with an intermediate step that produces cyanic acid and other by-products including cyanuric acid, ammeline and ammelid. It is 66% nitrogen by molecular weight and usually combined with formaldehyde to produce melamine resin (durable plastic) and melamine foam (polymeric cleanser) in the industry. Products that contain melamine include countertops, dry erase boards, fabrics, glues, housewares and flame retardants, inks among many others. In addition, it is a derivative of arsenical drugs (e.g. Melarsoprol – used to treat trypanosomiasis) and can be used in fertilizers. Cattle were once fed feed containing melamine as a nitrogen source but it has since been proven to be ineffective due to slow hydrolysis in ruminants.

Why was melamine added to milk products?

This was done in order to boost protein content of milk products when tested by the Kjeldahl method which tests nitrogen in all organic nitrogenous compounds. With every addition of 1g of melamine to 1L of milk, the protein content is falsely increase by 0.4%. This can be used to pass quality checks of such products before consumer market distribution even if the milk product produced itself does not have a high protein content.

Workings of the Kjeldahl method: nitrogen in the assay reacts with sulfuric acid to form ammonium sulfate. Small amounts of sodium hydroxide are added to covert ammonium salt back to ammonia. Ammonia is reacted with sulfuric acid again, and the remaining acid is quantified by adding sodium carbonate with a methyl orange pH indicator to quantify the amount of ammonium salt.

How does it adversely affect consumers?

While some remained asymptomatic, most had urinary stones, dysuria, difficulty in urination, renal coli and hematuria while more severe cases experiences hypertension, edema and oliguria. However, when combined with cyanuric acid (may also be present in melamine powder as it is a by-product of melamine synthesis), gives rise to crystals that lead to development of kidney stones that block the small tubes in the kidney and stop production of urine which lead to kidney failure and eventually, death. It is also interesting to note that while melamine has also been proven to have carcinogenic effects in animals, there is no sufficient evidence that it affects humans in the same way.

Dilated distal cat tubule with melamine/cyanuric acid crystals (A) and fragmented crystals (B) respectively

Is there treatment for kidney stones and kidney failure?

Depending on the severity of the effects, treatment may include infusion of fluids, urine alkalinisation, correction of electrolyte and acid-base disturbance, haemodialysis, peritoneal dialysis or surgical removal of kidney stones.

References:
>> Journal of the American Society of Nephrology, 2009. Melamine Toxicity and the Kidney. [online] Available at: <http://jasn.asnjournals.org/content/20/2/245.full?sid=301c79ef-7aab-4d0a-8981-a5994124434c> [Accessed 25 January 2013]
>> World Health Organization, 2013. Questions and Answers on Melamine. [online] Available at: <http://www.who.int/csr/media/faq/QAmelamine/en/index.html> [Accessed 25 January 2013]
>> U.S. Food and Drug Administration, 2011. Melamine in Tableware: Questions and Answers. [online] Available at: <http://www.fda.gov/Food/ResourcesForYou/Consumers/ucm199525.htm> [Accessed 25 January 2013]

Images obtained from:
>>http://jasn.asnjournals.org/content/20/2/245.full?sid=301c79ef-7aab-4d0a-8981-a5994124434c