Nancy Johnson has lived near the Salton Sea her entire life. Her grandparents originally moved to the area at the behest of their doctors, who said the hot, dry desert was the perfect antidote for their emphysema. Now, as the principal of Westmorland Union Elementary School, Johnson faces an entirely different set of circumstances. She’s responsible for 380 of Imperial County’s most vulnerable residents — children between the ages of 5 and 11 — and 17 percent of her student body has asthma. The air quality is so poor that the county ranks first in California for asthma-related emergency room visits for children.