Dr. Mahowald explained that when you release a plume of iron vapor, the iron rapidly reacts with oxygen in the air to condense into iron oxide particles. “Iron oxide particles aren’t particularly hazardous for air quality,” she said, although if there are enough of them, they could certainly be bad for your lungs. That’s not necessarily because of any properties specific to iron oxide—it’s just that your lungs are designed to breathe air.
