The problems in Asia are not limited to China. Ice cream and sweets made with the same industrial dyes used for coloring garments have been found outside schools, and farmers have been caught dipping fruits in herbicide, to add shine, a day before going to market.
In India, pesticides often taint groundwater and produce. Coca-Cola and Pepsi have been dueling with a New Delhi environmental group, which alleged it found unacceptable levels of pesticides in soft drinks.
Street food is another problem. Millions grab everything from chicken kebabs to rice porridge from unregulated food stalls where hygiene is often poor. Unsafe preservatives are sometimes added, and vendors typically use the cheapest oils and ingredients.
But the food is hot, cheap and tasty - a combination that often overrides safety concerns in countries where many still live on $2 a day.
"Asking for food quality would be a luxury," said Alex Hillebrand, chemical and food safety adviser at WHO's regional office in New Delhi. "They're hungry people."
Some countries, such as Thailand, are trying to improve domestic food safety. In bustling Bangkok, where pots bubble and woks sizzle at makeshift kitchens pitched on sidewalks, markets are issued test kits that can detect up to 22 contaminants.
No one knows the extent of chemical-laced food in Asia or how it will affect public health.
"It might be that you consume it today, but you don't see any effects for 10 years," said Peter Sousa Hoejskov, a food quality and safety officer at the U.N. Food and Agriculture Organization in Thailand. "Some foods have issues that are developing over a long, long time and others you have an immediate reaction."
China has faced outrage among its own citizens in recent years. Whiskey laced with methanol, a toxic wood alcohol, was blamed for killing at least 11 people in southern Guangzhou. Local media in Shanghai uncovered the sale of phony tofu made from gypsum, paint and starch.
At least a dozen Chinese babies died and more than 200 were sickened with symptoms associated with malnutrition after drinking infant formula made of sugar and starch with few nutrients. In another case, lard for human consumption was made with hog slop, sewage, pesticides and recycled industrial oil.
Some Vietnamese have been so shaken by news of tainted Chinese foods, they are changing their eating habits. They are avoiding Chinese-made products and paying more - up to $2 a bowl - for pho at an air-conditioned chain restaurant with signs promising no formaldehyde or borax.
"I am very, very worried about it," said Duong Thuy Quynh, 31, who was eating beef pho because she was also worried about bird flu in chicken. "I'm ready to pay more to protect myself and my family."
