A row that began a year ago when Taiwan rejected Chinese crabs containing a banned substance has spread to other imports from pork to wheat, raising the ire of trading partners who accuse the country of protectionism.
Taiwan says that concerns for the public health are behind tougher inspection standards, which trace their roots back to last fall when crabs from China were found to contain traces of the banned antibiotic nitrofuran.
The new policy has already threatened the wheat imports - upon which it relies to meet its milling needs, cutting market access for U.S. producers who are the island's largest foreign suppliers.
The media have reported over the last week new cases, including discovery of traces of banned substances in U.S. strawberries and Canadian pig kidneys.
Critics say the sudden strict enforcement of a zero-tolerance policy may be motivated in part by local farmers looking to protect their livelihood.
"Pork farmers, who in recent years have suffered from low prices and soaring costs of feed, take their argument to the parliament, which pressures the government to act, said Roy Lee, assistant executive director WTO center at the Chung-Hua Institution for Economic Research.
Last year's row over hairy crabs from Shanghai brought imports of the delicacy to a halt during last fall's high season -- a development that looks set to continue into the current season as both sides remain at an impasse.
Some believe the media uproar that followed the crab discovery may have spurred the government to ban a number of fat-reducing drugs in 2006.
Taiwan also replaced its previous "monitor only" policy in July with a more active testing on bulk commodities such as wheat and corn, again with a zero-tolerance for banned substances.
As a result, Taiwan rejected 24 metric tons of U.S. pork imports in July after it discovered traces of the banned ractopamine drug, which is used to promote lean muscle growth.
The United States is the leading pork supplier to Taiwan and is expected to provide 58 percent of the estimated 45,000 metric tons of imported pork in 2007, according to the USDA.
Wheat purchases from the United States were also disrupted in July when officials detected small amounts of the pesticide malathion.
"The penalty of a couple of noncompliant shipments may quickly be elevated to become an import suspension of the commodity, not only on the offended import brand, and to punish the imports from a source country, instead of a specific company," said the USDA in a report published early in September.
The U.S. Department of Agriculture's foreign service described the new policy as ambiguous and stringent, while China described the policy as politically driven.
Bowing to pressure from the United States, the health department announced in August that it would ease its zero-tolerance policy, prompting vocal protests in the streets of the capital Taipei.
As the island is completely reliant on imports to meet its milling needs, the government relented and permitted residue from the pesticide amounting to no more than 0.5 parts per million.
But wheat importers say the level is still well below the 8 ppm in the United States, which could lead to continued wheat supply disruptions.
Lawmakers forced health officials to suspend any action on the ban pending a decision by the Council of Agriculture, which is seen as sympathetic to the farmers.
Some see the original row with China as politically motivated, with Taiwan's independence-leaning government banning a popular food item imported from a political and military rival.
"We have noticed that a certain group in Taiwan is trying to discredit mainland foods. Such politically driven action will greatly harm normal trade across the Strait," Li Weiyi, spokesman of the Taiwan Affairs Office was quoted as saying in the China Daily last week.