The World Health Organization (WHO) has called for a global ban on smoking at work and in enclosed public places.

The United Nations agency said a ban will help limit non-smokers' exposure to secondhand smoke, which can kill through heart disease and serious respiratory and cardiovascular illness.

"The evidence is clear, there is no safe level of exposure to secondhand tobacco smoke," WHO Director-General Margaret Chan said in a statement ahead of World No Tobacco Day, which will be observed today for the 18th year.

"Many countries have already taken action. I urge all countries that have not yet done so to take this immediate and important step to protect the health of all," she said.

A number of EU countries, including France, Spain, Ireland and Portugal are among those to have introduced such bans.

The Geneva-based agency said its recommendation was based on three studies on secondhand smoke, two in the United States and one by the International Agency for Research on Cancer.

"By July 1, 240 million people worldwide will be protected by smoke-free legislation," Wayne Kao of the International Union against Cancer, which supports a smoke-free world, said.

"Unfortunately, that is less than 4 percent of the world population," Kao told a news conference.

In addition to several European countries, New Zealand, Bermuda, Uruguay and parts of Australia, Canada and the United States have banned smoking in public places, Kao said.

The WHO said some 200,000 workers die each year due to exposure to tobacco smoke at work, while around 700 million children, around half the world's total, breathe air polluted by tobacco smoke, particularly in the home.

The agency said that tobacco is the leading cause of preventable deaths worldwide. The number of smokers is rising rapidly in developing countries.

"Remove the pollutant - tobacco smoke - by implementing 100-percent smoke-free environments. Ventilation and smoking areas do not reduce exposure to a safe level of risk," Armando Peruga, head of the WHO's Tobacco Free Initiative, told reporters.

Member countries of an international treaty against smoking, the 2003 WHO-backed Framework Convention on Tobacco Control, are due to discuss guidelines on exposure to secondhand smoke at a meeting in Bangkok, Thailand starting on June 30.

(Agencies via Xinhua News Agency May 31, 2007)