Argentina is one of the world's largest exporters of genetically-modified soya. It's big business, but some local residents fear herbicides used by the industry could be making them sick.

Horacio Brignone lives in the village of María Juana in the Argentine flatlands, or pampas. From his window he can see fields of soya.

His 20-year old son has suffered from asthma since he was three years old, he says, but when he recently moved to a city the condition disappeared.

"He hasn't had an attack for two years since he went to study in Córdoba," says Horacio. "But when he came home for two months recently, he began to cough again."

He blames the weedkiller sprayed on the soya fields.

"We are 50m from the fields," Mr Brignone says. "We can't be certain, but respiratory problems and skin complaints are very common round here among those who live very close to the fields."

Mr Brignone's wife, Rosalía Ramonda, has suffered from rashes on her skin for years.