Nation: Panic over Paraquat

The bizarre case of the polluted pot

The soldiers used to climb for hours in the hot sun to reach the marijuana and opium poppies hidden in the Mexican Sierra Madre. Then they had to hack up the crop with machetes and burn it. Starting in 1975, the U.S. made their work easier by providing blue and white helicopters (Bell 212s and 206s), purchased at a cost of about $21 million; some of the helicopters were used to spray herbicides from a few feet above the ground. Others served as gun ships, hovering above...