Investigation uncovers how chemicals like diquat, banned in the UK but legal to export, are causing health problems in the global sout

Valdemar Postanovicz was at home after a day tending to his tobacco crop when his limbs seized up. “All of the right side of my body was paralysed. I couldn’t feel my foot and my hand. My mouth twisted to the right,” he says.

He feared it was a stroke. In fact, he was suffering ­symptoms of acute ­pesticide poisoning. Postanovicz, 45, had absorbed Reglone, a powerful herbicide based on the chemical diquat. “It was only one time in my life, but I felt so sick,” he says.