The spat between the US and China over contaminated food exports highlights a rapidly spreading battle line in the world economy: the use of product standards to regulate, and some would say stifle, international trade.

Such "non-tariff barriers", particularly food standards, are frequently both more important and harder to eliminate than simple tariffs. Arguments frequently descend into a mire of competing scientific claims about safety and risk in which trade negotiators - let alone ministers and the general public - risk drowning in complexity. And while consumers' patriotic desire to protect domestic farmers or manufacturers requires some degree of altruism, given the higher prices this entails, fears of being poisoned by foreign food appeal directly to their self-interest.