Margaret Chan, WHO director-general, said the United Nations agency receives about 200 reports of tainted food products each month in its 193 member states.
But many food-borne diseases go unreported and outbreaks of salmonella or E. coli bacteria can take on massive proportions according to the WHO, which backs "farm to fork" food safety.
"I have to say that food safety is a big problem for both developed and developing countries," Chan told a news briefing, adding that the WHO was working with countries to strengthen their regulatory frameworks."
China, where poorly regulated food and drug safety standards have been a problem for years, is reeling from health scandals. Chinese authorities told food and drug companies to put safety first and urged the media to paint a rosier picture.
Patients in Panama have died from mislabeled chemicals in medicines from China and pets died in the United States from substandard feed, while tainted Chinese toothpaste was found in Central America and elsewhere.
But Jorgen Schlundt, director of the WHO's department of food safety, said China had been seriously addressing shortcomings since 2001 and was starting to implement some of the WHO's suggestions.
High level political commitment
"They are working on it. There is a high-level political commitment to do something about it," Schlundt told Reuters, stressing that food safety was an issue in all countries. "We are not expressing any concern especially about China."
"China has realized some time ago the need for updating its food safety system. It takes a long time to update a system, not only for China. After the BSE crisis, it took the UK a long time," he added.
BSE, bovine spongiform encephalopathy or mad cow disease, is a fatal brain disease of cattle that emerged in Britain in 1986 and can cause variant Creutzfeldt-Jakob disease in humans.
Since 1963, the Codex Alimentarius Commission set up by the WHO and the U.N. Food and Agriculture Organisation has developed food standards and codes of practice to protect health worldwide.
The WHO also issues about 10 to 20 "emergency notifications" each year, signaling a potential international public health problem linked to food, according to Schlundt.
Most relate to problems in industrial countries, which have better systems for reporting disease outbreaks, and the figures do not indicate the true extent of problems elsewhere, he said.
"A number of developing countries have very weak food safety because it hasn't been a priority," he said, citing gaps in sub-Saharan Africa as well as parts of Latin America.
The WHO alerted its membership last September to an outbreak of the diarrheal disease E. coli 0157 in spinach in the United States, which had caused 205 cases including three deaths.
It acted on information from the U.S. Food and Drug Administration that the spinach, sold to Canada and Mexico, had later been distributed to other countries including China.