Twelve years ago, 300,000 children in China were poisoned after drinking infant milk formula that contained melamine, a chemical used in plastic. Six babies were killed by the toxic substance, which was used by 22 companies to artificially boost the protein levels that showed up in nutrition tests.

The maximum residual level of melamine content in infant formula has been legally regulated at 1 mg/kg by the Food and Drug Administration (FDA) and World Health Organization (WHO) (14-16). A new tolerable daily intake for melamine was established at 0.2 mg/kg body weight by the WHO in 2008 (15).

The chemical was used to increase the nitrogen content of diluted milk, giving it the appearance of higher protein content in order to pass quality control testing.

Separately, a third major formula maker — Abbott Laboratories, whose brands include Similac — told AP in November that in-house tests had detected trace levels of melamine in its infant formula.