American farmers and food processors usually take a lot of pride in what they grow and package, and where they grow and package it. Foreign growers and packers, not so much. Sometimes they don’t want the shopper to know where it comes from.

This week the World Trade Organization is expected to uphold Canadian and Mexican complaints that U.S. laws requiring a label of origin are discriminatory. These across-the-border neighbors complain that such labeling is needlessly expensive, unnecessary when there’s such heavy traffic in livestock at different stages of marketing moving back and forth across the border, and it gives American producers unfair advantage in violation of North American trade pacts.

Complicated arguments make it difficult for supermarket shoppers to know where the ordinary customer’s best interests lie.

Processed foods do not require country of origin labeling, particularly if the food is repackaged once it arrives in the United States. With imports of processed foods rising steadily rate, there’s concern that much of this rising volume originates in China, which does not always meet American standards.

Given the pollution of the Chinese environment - official Chinese government statements reveal that more than half of the water in China is polluted, for example - these imports could be a disaster waiting to happen. American importers insist that their standards are being met in Chinese processing, but this requires at least a small leap of faith.

An earlier episode is worth recalling. In March 2007 kidney failure in dogs and cats was traced to ingredients in pet food from a Chinese company, killing at least 3,600 animals. There’s no central reporting of animal deaths in China, but there are estimates that the deaths of pets traced to contaminated Chinese ingredients could run to many thousands. At that time, Chinese protein exports to the United States for human consumption were brought under inspection.

Since then, Chinese levels of pollution have continued to rise, with weekly reports even in the closely controlled Chinese media of food contamination scandals. The general problem of air, water and ground pollution is finally being addressed by the Beijing government, though it is not clear how effective this will be.

Retreating from labeling the country of origin of food sold in the United States, however argued for economic reasons, is a cause for concern. Further identifying the country of origin of all foodstuffs, raw or processed, is the best way to help a careful consumer to protect his or her family.