Ebocha, Nigeria - Justice Eta, 14 months old, held out his tiny thumb. An ink spot certified that he had been immunized against polio and measles, thanks to a vaccination drive supported by the Bill & Melinda Gates Foundation. But polio is not the only threat Justice faces. Almost since birth, he has had respiratory trouble. His neighbors call it "the cough." People blame fumes and soot spewing from flames that tower 300 feet into the air over a nearby oil plant. It is owned by the Italian petroleum giant Eni, whose investors include the Bill & Melinda Gates Foundation....