PANAMA — Eduardo Arias hardly fits the profile of someone capable of humbling one of the world’s most formidable economic powers.

A 51-year-old Kuna Indian, Mr. Arias grew up on a reservation paddling dugout canoes near his home on one of the San Blas islands off Panama’s Caribbean coast. He now lives in a small apartment above a food stand in Panama, the nation’s capital, also known as Panama City.

But one Saturday morning in May, Eduardo Arias did something that would reverberate across six continents. He read the label on a 59-cent tube of toothpaste. On it were two words that had been overlooked by government inspectors and health authorities in dozens of countries: diethylene glycol, the same sweet-tasting, poisonous ingredient in antifreeze that had been mixed into cold syrup here, killing or disabling at least 138 Panamanians last year.

Mr. Arias reported his discovery, setting off a worldwide hunt for tainted toothpaste that turned out to be manufactured in China. Health alerts have now been issued in 34 countries, from Vietnam to Kenya, from Tonga in the Pacific to Turks and Caicos in the Caribbean. Canada found 24 contaminated brands and New Zealand found 16. Japan had 20 million tubes. Officials in the United States unwittingly gave the toothpaste to prisoners, the mentally disabled and troubled youths. Hospitals gave it to the sick, while high-end hotels gave it to the wealthy.