Wildfires and other large fires seem to be more common events. Other than the property damage they do, the harm to humans from the smoke is getting renewed attention. A Harvard study is the first to examine specific immune damage. The study, in the journal Nature Medicine, found immune system damage from the complex collection of gases, particulates and toxins in fire smoke affects even healthy people. These cellular changes confirm previously known harm to respiratory, cardiac and neurological systems. It also provides greater understanding of possible harm to pregnant women. Authors say knowing details about fire smoke harm could help public health organizations and individuals take action to mitigate or prevent smoke damage altogether.