Nature World: According to the American Lung Association (ALA), more than half of the American population resides in "unhealthy hot spots." Are you one of them? In its annual "State of the Air" report for 2016, ALA rounds out the cities with the most polluted air by considering two types of air pollution: ozone and particle pollution, measured in short-term spikes and year-long average. Of the total American population, there is an estimated number of 166 million Americans at risk of premature death, the report...