Wildfire smoke is an emerging nationwide crisis for the United States. Supercharged by climate change, blazes are swelling into monsters that consume vast landscapes and entire towns. A growing body of evidence reveals that these conflagrations are killing far more people than previously known, as smoke travels hundreds or even thousands of miles, aggravating conditions like asthma and heart disease. One study, for instance, estimated that January’s infernos in Los Angeles didn’t kill 30 people, as the official tally reckons, but 440 or more once you factor in the smoke. Another recent study estimated that wildfire haze already kills 40,000 Americans a year, which could increase to 71,000 by 2050.