Half the population of Pakistan are at risk of disability, mental illness and death because of a lack of iodine in their food.

The BBC's Richard Galpin reports from Pakistan

The United Nations, aid agencies and the government have launched a big publicity campaign to encourage Pakistanis to eat salt which contains extra iodine.

The chemical occurs naturally in the soil and gets into the food chain, but in Pakistan floods and soil erosion means people are not getting the amount they need.

Iodine is essential for the healthy development of children.

Without it, they are at risk of developing goitre - a swelling of the thyroid gland which controls growth, mental illness and disability.

Thyroid problems can lead to cretinism.

Some 65 million people - half the population - are said to be at risk.

Goitre

According to Dr Sadar-ul-Mulk, a doctor in the mountainous northern region which is most affected by iodine deficiency, the problem can lead to still births and infant deaths.

"This is affecting the health of growing children. A large percentage of children - up to 20% - have goitre here.

"Many mothers lose their babies before time and a large number of infants die prematurely," he said.

Adding iodine to salt can prevent deficiency

Doctors are calling for international aid to help fund a screening programme to detect iodine deficiency in babies.

Many children with iodine deficiencies end up begging on the street.

This is because there are no support networks for their families.

Unicef's director in Pakistan, Steve Umay-moto, said: "I assume some of the children seen abandoned have been thrown out by their families.

"Some do not survive very well or very long."

Added iodine

However, there is a cheap and simple solution to the problem: getting processors to add iodine to salt.

But despite a four-year campaign to convince people of the benefits of eating iodised salt, less than a quarter of families buy it.

The government has had to delay its salt iodisation programme.

It now says it will get all salt to include extra iodine by 2003.

Flooding in Pakistan has helped deplete a natural source of iodine

But it will still be a difficult task convincing salt processors to cooperate given the low uptake from consumers.

Many are small businesses and they need to make a profit.

Only a third of salt in Pakistan is currently iodised.

Dr Mushtaq Kan, a government nutrition specialist, says extra resources will be needed to ensure the targets are met.