The newest revelations on melamine toxicity involves vegetables that are sprayed with the insecticide cyromazine. This derivative of melamine degrades back into melamine resulting in the contamination.
Hong Kong said last week it would test meat, vegetables and processed food for melamine, a move that underlines concerns about food safety in the former British colony which returned to Chinese rule in 1997.
It imposed a cap on melamine in September, restricting it to no more than 2.5 milligrams per kilogram, while melamine found in food meant for children under three and lactating mothers should be no higher than one mg per kg.
The level of melamine found in the eggs was 4.7 mg per kg, the newspapers said.
Cyromazine itself apparently has very little toxicity:
Recently, experts have investigated and confirmed that melamine has also been found in lettuce, water cress, tomatoes, mushrooms, potatoes and other agricultural products. There is 17 milligrams (0.000037 lbs) of melamine per kilogram (2.20 lbs) of mushrooms.
Cyromazine is practically nontoxic (acutely) to mammals and birds. Exposure estimates for these organisms are 0.05 ppm. Acute toxicity for birds is 1785 ppm maximum. Safety factor is 105-106 for birds. Acute toxicity for mammals is 1000 ppm maximum. Safety factor is again 105 - 106.