Deal reached on deadly chemicals

DDT is the most controversial of the chemicals

Delegates from more than 120 countries have reached a deal aimed at cutting what are regarded as some of the world's most dangerous chemicals.

The agreement was struck after hours of talks at a United Nations conference held in Johannesburg, paving the way for an international convention.

This new treaty will protect present and future generations from the cancers, birth defects and other tragedies caused by Pops

Conference chairman John Buccini

It means the use of the chemicals, classed as Persistent Organic Pollutants (Pops), will be banned or severely restricted.

These chemicals have been linked to cancer, sterility and birth defects, and are now banned by many governments.

Twelve chemicals were the particular focus of the conference's concerns, including the controversial pesticide DDT.

Role for DDT

DDT has been used for more than 50 years to control malaria-carrying mosquitoes, but its use has been curtailed after studies suggested it was a factor in a wide range of medical conditions.

Many Pops are used for crop treatment

Conservationists say DDT and its breakdown product, DDE, have been shown in laboratory tests to affect animals' nervous, immune and reproductive systems.

But some health experts say restricting the use of DDT has led to a rise in malaria, which represents a greater risk to health than the chemical's side-effects.

Despite the opposing views, a consensus is said to have emerged at the Johannesburg talks that DDT should not be phased out without the development of effective alternatives for controlling malaria.

"This new treaty will protect present and future generations from the cancers, birth defects and other tragedies caused by Pops," said conference chairman John Buccini of Canada in a statement announcing the agreement.

'Solid foundation'

The deal caps five rounds of talks held over two-and-a-half years.

The convention will be signed in Stockholm in May and become a legally binding treaty once it has been signed by 50 countries. Mr Buccini said this should be achieved within four or five years.

The agreement was praised by some of the conservationists who had attended the talks as observers.

"It's a strong treaty. It's a real solid foundation for the future," said Clifton Curtis of the Worldwide Fund for Nature.

Pops differ from other pollutants because they are extremely difficult to break down. They can persist in the environment for many years, and can be absorbed by plants and animals.

Some of them are by-products of industry, others are man-made pesticides, used as treatments for crops and in timber preservation or to attack pests directly.