Recurring wildfires are sparking concern among medical experts about potentially major health consequences. Worsening asthma, lung disease and even heart attacks in heart disease patients have all been linked with previous fires. But blazes that used to be seasonal are happening nearly year-round and increasingly spreading into cities. That’s exposing many more people to choking smoke that contains many of the same toxic ingredients as urban air pollution. Heart problems and cancer have been linked with exposure to smog. Scientists worry that repeated exposure to wildfire smoke might carry the same risks.