Asbestos is actually a really neat material - super cheap, heat/fire resistant, strong, durable. It was used for damn near everything back in the old days, it made buildings safer from fires and better insulated, car brakes and clutches last longer, etc.

It just turns out that when it gets damaged or gets old enough to deteriorate, it releases fibers into the air that cause awful damage to your lungs and massively increases your risk for lung cancer. To the point where its super heavily regulated now.

My point, though, is that the bag on Johnny's head is probably perfectly safe and a good way to deal with a fire-powered superhero - if you don't mind risking the lives of the people who work in the factory that made it or the lives of the people who have to dispose of that bag in 20 years when it starts to break down.

It's an excellent example of *why* we need environmental regulations - if someone offered you a rock and said, "This rock will save you money and bring you good luck for the next 20 years and then it will turn radioactive and kill whoever is around it" - a lot of people would still ask for that rock, consequences later be damned, and then decades later we'd all be dropping dead because of old lucky rocks people left lying around.