Dust storms laced with toxins sweep across California’s Imperial County, where mud volcanoes spit and hiss near the shores of the slowly shrinking lake known as the Salton Sea. The county is one of California’s poorest, most of its jobs tied to a thin strip of irrigated land surrounded by desert. San Diego and the Golden State’s prosperous coast lie only 100 miles away across a jumble of mountains, but it might as well be another world.