Here's the bottom line:
In February 2009, tests for Fonterra showed melamine contamination in imported raw ferric pyrophosphate compound used in making milkpowder. NZFSA waited until it had the results of the testing commissioned by Fonterra before alerting the public, when it said the levels were too low to cause health problems.
Dr Reeve said today testing methods are now so sophisticated, melamine can be detected at tiny levels where contamination was not deliberate.
"A zero limit for the compound would not be practical and could be used as a technical barrier to trade," he said in a statement.