American biotechnology has turned Argentina into the world's third-largest soybean producer, but the chemicals powering the boom aren't confined to soy and cotton and corn fields. The Associated Press documented dozens of cases around the country where poisons are applied in ways unanticipated by regulatory science or specifically banned by existing law. The spray drifts into schools and homes and settles over water sources; farmworkers mix poisons with no protective gear; villagers store water in pesticide containers that should have been destroyed. Now doctors are warning that uncontrolled pesticide applications could be the cause of growing health problems among the 12 million people who live in the South American nation's vast farm belt. In Santa Fe, cancer rates are two times to four times higher than the national average. In Chaco, birth defects quadrupled in the decade after biotechnology dramatically expanded farming in Argentina. A nation once known for its grass-fed beef has undergone a remarkable transformation since 1996, when the St. Louis-based Monsanto Co. promised that adopting its patented seeds and chemicals would increase crop yields and lower pesticide use. Today, Argentina's entire soy crop and nearly all its corn and cotton are genetically modified, with soy cultivation alone tripling to 47 million acres. Agrochemical use did decline at first, then it bounced back, increasing ninefold from 9 million gallons in 1990 to more than 84 million gallons today as farmers squeezed in more harvests and pests became resistant to the poisons.