"As ozone depletion becomes more marked, and as people around the world engage more in sun-seeking behavior, the risk of health complications from over-exposure to ultra-violet radiation is becoming a substantial public health concern," said WHO Director-General Lee Jong-wook.

By reducing the time children and adolescents are exposed to direct sunlight, he said, "we can substantially reduce the risk of contracting skin cancers, cataracts and other conditions which might only appear much later in life."

In its 2002 World Health Report, the WHO said that around the world an average of 66,000 people died every year from melanoma or other types of skin cancer.

Independent scientific research shows that every year there are between two to three million new cases of non-malignant melanoma and around 130,000 malignant - and normally fatal - new full-blown skin cancer cases.

Although most known skin cancers seemed to occur in the industrialized world, WHO radiation and environmental health specialist Mike Repacholi told a news conference, there were believed to be many unreported in poorer countries.

Although people with darker skins were less susceptible to skin cancers, they were just as likely to contract eye cataracts as fairer-skinned populations, and people living close to the equator were even more likely to develop them.

Under the school plan, dubbed the Intersun Project, the two agencies will distribute packages showing teachers how to develop their own sun education programs, the WHO said.

In a joint statement from the two agencies which also marked the International Day for the Preservation of the Ozone Layer, UNEP Executive Director Klaus Toepfer said latest studies showed the protective shield was on the road to recovery.

This was the result of international agreements over the past two decades to phase out use of various chemicals - like those used in some pesticides, refrigerators and aerosols.

"But we must remain vigilant and more needs to be done before we can say that the problem is solved for good," said Toepfer. This included stopping illegal trade in banned chemicals and enforcing the agreements in developing countries.