What Melamine Is
Melamine (CAS 108-78-1) is an organic base with the formula C3H6N6 and a molar mass of 126.12 g/mol. It contains about 66.6 percent nitrogen by mass, which explains both its value in resin chemistry and the misuse that made it notorious in food adulteration. The commercial product is a white crystalline powder with a bulk density in the range of 700 to 900 kg/m3. On heating it does not melt cleanly; it sublimes and decomposes above roughly 300 C, releasing nitrogen oxides and ammonia.
How Human Exposure Occurs
In industrial settings, exposure of workers is mainly by inhalation of dust during bagging, conveying and mixing, and by skin contact with the powder. For consumers, the relevant routes are migration from melamine-formaldehyde tableware into hot or acidic food and drink, and, historically, deliberate addition to milk and infant formula to inflate the apparent protein content measured by the Kjeldahl method. The industrial substance itself has low acute oral toxicity, and animal studies show that the parent compound is not readily metabolised in mammals.
Why the Cyanuric Acid Combination Matters
The health concern is not melamine alone but its behaviour in combination with cyanuric acid, a related triazine used in the same adulteration practices and also present in some chlorinated water systems. When both substances are present, they co-crystallise in the kidney tubules to form insoluble melamine cyanurate stones. This can block urine flow and lead to acute kidney injury, the effect seen in the reported pet food and infant formula incidents. That mechanism is why risk assessment for melamine focuses on combined exposure and on susceptible groups such as infants.
Industrial Applications of Melamine
Most melamine is converted into melamine-formaldehyde resin. The resin is used in decorative laminates and worktops, in plywood and panel adhesives, in moulding compounds for electrical components and in surface coatings that must resist heat and abrasion. Melamine is also used as a flame-retardant component, in the form of melamine cyanurate for unfilled polyamides and in intumescent systems for coatings, and it appears as a crosslinker and as a component of slow-release fertiliser. In these applications the substance is fully reacted into a thermoset network, which is why the finished article behaves very differently from the free powder.
Regulatory Limits and Quality Grades
Two limits are quoted most often in trade. The World Health Organization expert consultation of 2008 set a tolerable daily intake of 0.2 mg per kg of body weight, a value intended to protect against the crystallisation mechanism rather than against acute toxicity. For food contact plastics, the European framework sets a specific migration limit of 2.5 mg per kg for melamine, which suppliers of tableware must demonstrate by migration testing at the temperature and contact time of the intended use. Industrial melamine is traded against a national standard for industrial melamine that grades the material by purity, moisture, ash, colour and content of the related triazines, and the raw material is routinely checked by high-performance liquid chromatography and by nitrogen determination.
Frequently Asked Questions
Q: Is melamine harmful to humans?
A: The substance has low acute toxicity, but it is harmful when ingested together with cyanuric acid, because the two form insoluble crystals in the kidneys that can cause acute kidney injury.
Q: What is the safe intake level for melamine?
A: The World Health Organization expert consultation of 2008 set a tolerable daily intake of 0.2 mg per kg of body weight, applying to total intake from food and food contact materials.
Q: Can melamine migrate from tableware into food?
A: Yes, particularly at high temperature or with acidic food. Food contact plastics are regulated by a specific migration limit of 2.5 mg per kg, verified by migration testing on the finished article.
Q: What is melamine mainly used for?
A: Its largest use is melamine-formaldehyde resin for laminates, adhesives, moulding compounds and coatings; smaller volumes go to flame retardants, crosslinkers and fertilisers.
Q: Are workers at risk when handling the powder?
A: The main risks are dust inhalation and skin contact, so local exhaust ventilation, dust masks, gloves and eye protection are standard practice in bagging and mixing areas.
Q: How is industrial melamine graded and tested?
A: Grades are defined by a national industrial standard that sets purity, moisture, ash and colour limits, and testing is carried out by liquid chromatography together with nitrogen determination and moisture measurement.