Food safety is an issue in Asia where hot weather, a lack of refrigeration and the demand for street food drives vendors to use inexpensive ways to preserve their products despite health risks.

"I think if we don't see those chemicals being put in the food with our own eyes, then we can just smack our lips and pretend that there are no chemicals in the food," said Nguyen Van Ninh, devouring a 30-cent bowl of "pho" on a busy Hanoi sidewalk in Vietnam. "Why worry about it?"

While the discovery of tainted imports from China has shocked Westerners, food safety has long been a problem in much of Asia, where enforcement is lax and food poisoning deaths are not unusual. Hot weather, lack of refrigeration and demand for cheap street food drives vendors and producers to find inexpensive - and often dangerous - ways to preserve their products.

What's exported, for the most part, is the good stuff. Companies know they must meet certain standards if they want to make money. But in the domestic market, substandard items and adulterated foods abound, including items rejected for export.

Formaldehyde, for instance, has long been used to lengthen the shelf life of rice noodles and tofu in some Asian countries, even though it can cause liver, nerve and kidney damage. The chemical, often used in embalming, was found a few years ago in seven of 10 pho noodle factories in Hanoi.

Borax, found in everything from detergent to Fiberglas, is also commonly used to preserve fish and meats in Indonesia and elsewhere. Farmers in various countries often spray produce with banned pesticides, such as DDT.

"The people who do this want to make money. And if they're stupid and greedy, this is a bad combination," said Gerald Moy, a food safety expert at the World Health Organization in Geneva. "It's the wild West."

The quality of Asian food has come under harsh scrutiny after toxic substances were discovered in several Chinese exports.

Wheat gluten tainted with the industrial chemical melamine has been blamed for killing or sickening thousands of dogs and cats in North America. Fish containing pufferfish toxins, drug-laced frozen eel and juice spiked with harmful dyes were among other unsafe products shipped to the U.S.

Diethylene glycol, a sweet-tasting thickening agent also used in antifreeze, has been blamed for the deaths of at least 51 people in Panama after the chemical was imported from China and mixed into cough syrup and other medicines. The U.S. Food and Drug Administration has halted all shipments of Chinese toothpaste to test for the same chemical reportedly found in tubes sold in Australia, the Dominican Republic and Panama.

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."