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http://www.cfsan.fda.gov/~dms/melamra.html

The point of departure (POD) is the no-observed-adverse-effect-level (NOAEL) of 63 mg/kg/day from the rodent subchronic bioassay. This POD was then divided by two 10-fold safety/uncertainty factors (SF/UF) to account for inter- and intra-species sensitivity, for a total SF/UF of 100. The resulting Tolerable Daily Intake (TDI) is 0.63 mg/kg bw/day. The TDI is defined as the estimated maximum amount of an agent to which individuals in a population may be exposed daily over their lifetimes without an appreciable health risk with respect to the endpoint from which the NOAEL is calculated.

http://www.efsa.europa.eu/EFSA/Statement/efsa_statement_melamine_en_rev1.pdf?ssbinary=true

In conclusion, melamine is not genotoxic, carcinogenic or teratogenic. The Scientific Committee of Food (SCF) derived a TDI of 0.5 mg/kg b.w. per day for food contact materials but no details were given for its derivation (EC, 1986). The recent U.S. FDA assessment supports this TDI since a NOAEL of 63 mg/kg b.w. per day was used to derive a TDI of 0.63 mg/kg b.w. per day using an uncertainty factor of 100 (US-FDA,
2007a).

CONCLUSIONS
The Scientific Committee of Food (SCF) derived a tolerable daily intake (TDI) of 0.5 mg/kg body weight (b.w.) per day for melamine for food contact materials but no details were given for its derivation. Recently the U.S. Food and Drug Administration (FDA) derived a TDI of 0.63 mg/kg b.w. per day which is in line with the TDI derived by the SCF. For melamine a specific migration limit of 30 mg/kg food was agreed by the SCF
assuming a maximum consumption of 1 kg food containing the substance for a 60 kg person.

Based on the NOAEL for sodium cyanurate derived from the 2-year study in rats of 154 mg/kg b.w. per day, a TDI of 1.5 mg/kg b.w. per day can be proposed using an uncertainty factor of 100. There is a lack of toxicity data for ammeline and ammelide. Because of the structural similarities to melamine these compounds have been assumed to be of equal potency.

In conclusion, EFSA provisionally recommends to apply a TDI of 0.5 mg/kg b.w. per day for the total of melamine and its analogues (ammeline, ammelide, cyanuric acid). Because of a lack of toxicity data in domestic animals, EFSA provisionally recommends to apply this tolerable intake level as established for humans also to domestic animals. A source of uncertainty is the combined toxicity of melamine and cyanuric acid and their possible synergistic effects in relation to the recently observed toxicity linked to the acute renal failure and death of pet animals (cats and dogs) in the U.S. This mechanism is currently under investigation.

Ocurrence data on melamine and its analogues in food and feed from Europe are needed to perform a comprehensive risk assessment.