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Description of key information

Melamine phosphate is of low acute oral toxicity as determined in a GLP and OECD-guideline compliant study with rats (van Huygevoort 2002). No indication of toxicity was observed at the limit dose of 2000 mg/kg bw. Absence of systemic toxicity upon acute inhalation is derived from a GLP and OECD guideline compliant study with melamine tested with an aerosol of 5.19 g/m³ ( Muijser 1998). Limited information obtained from secondary sources on melamine indicate low dermal toxicity of melamine (UNEP 1998). 

Key value for chemical safety assessment

Additional information

In the acute oral toxicity study (van Huygevoort, 2002) melamine phosphate was administered by oral gavage to three Wistar rats of each sex at 2000 mg/kg body weight. The study was performed under GLP and according to OECD testing guideline 423. Animals were subjected to daily observations and weekly determination of body weight. Macroscopic examination was performed after terminal sacrifice on day 15. No mortality occurred and no clinical signs of systemic toxicity were noted. The mean body weight gain shown by the animals over the study period was considered to be normal. No abnormalities were found at macroscopic post mortem examination of the animals. The study is adequate in design and reporting to fulfil the criteria as key study.

Melamine phosphate was not tested for acute dermal or inhalation toxicity. It is acceptable to derive the systemic toxicity from experimental data of melamine since both melamine and its phosphate salt have a high solubility in water and a log POWof less than 1 and phosphate is an abundant in cells and body fluids. In addition, the higher molecular weight of melamine phosphate compared to melamine gives a safety margin.

Since melamine does not undergo metabolism (Mast 1983), the acute dermal hazard can be derived from oral data unless high dermal absorption is expected. As the substance is strongly charged and has a log POWof -3, high dermal absorption is not expected. In the absence of acute oral toxicity of melamine phosphate, the LD50for acute dermal toxicity is expected to be above 2000 mg/kg bw. This is consistent with poorly documented information on acute dermal toxicity of melamine (Anon 1990, UNEP 1998).

Based on the acute inhalation study with melamine (Muijser 1998), no acute systemic inhalation toxicity is predicted for melamine phosphate. The substance reacts slightly acidic in water; a saturated solution of 3.9 g/L has a pH of 3.5. Therefore, slight local effects might be possible.

Justification for classification or non-classification

Dangerous Substance Directive (67/548/EEC)

The available studies are considered reliable and suitable for classification purposes under 67/548/EEC. As a result the substance is not considered to be classified for acute oral, dermal and inhalatory toxicity under Directive 67/548/EEC, as amended for the 28th time in Directive 2001/59/EC.

Classification, Labelling, and Packaging Regulation (EC) No. 1272/2008

The available experimental test data are reliable and suitable for classification purposes under Regulation 1272/2008. As a result the substance is not considered to be classified for acute oral, dermal or inhalatory toxicity under Regulation (EC) No. 1272/2008.