Mishandling products in the U.S. food supply-among the safest in the world-can make eating downright unhealthy. In our continuing Challenges for Humanity series, we also explore genetic engineering of food. Want disease-free grapes? Add a silkworm gene. How about vitamin enhanced rice? While the technology promises new ways to help feed the world, some see risks to the land and to human health

Scientists surveying Guyana's rivers find fish species healthy for now, but waters run brown from mining