A United Nations Food and Agriculture Organisation (FAO) report says the chemicals are a time bomb waiting to explode.

Africa Reporter Caroline Hawley: "An expensive business"

The report says agencies alone could not meet the clean-up costs and it appealed to the chemicals industry to help pay for what it described as a lethal legacy.

It gives two examples: In Poland, 65,000 tonnes of dangerous pesticides are stored and a further 23,000 tonnes are in Ukraine.

The FAO is still trying to calculate the extent of the problem across central and eastern Europe, the Middle East, Asia and Africa.

BBC Africa Reporter Caroline Hawley says 3,000 tonnes have been disposed of in a number of African and Middle Eastern countries, but it could take more than 30 years to make the region safe unless more is done now.

Stockpile threat

Many of the chemicals were donated as aid, but now they are either too old to use or have been subsequently banned.

The FAO says the chemical stockpiles threatened humans and the environment if they were not properly disposed of.

The Rome-based agency says metal drums containing the pesticides eventually corrode, leading to contamination of soil and water used for irrigation and drinking.

"These 'forgotten' stocks are a serious risk. They could cause an environmental tragedy in rural areas and big cities," a spokesman says.

"There is hardly any developing country that is not affected by the hazards of obsolete pesticides."

To clean up an area, waste is often re-packaged and shipped to other countries for incineration which, the FAO says, costs nearly $4,000 per tonne.