The fluxes used with lead-free solder release about 2.5x as much particulate matter into the air and has been linked in multiple studies to a variety of lung is

The fluxes used with lead-free solder release about 2.5x as much particulate matter into the air and has been linked in multiple studies to a variety of lung issues. Current recommendations in the USA when working with lead-free solder is to do so in a downward pressure clean room of class 100,000 or better, in a fume hood, or while wearing an appropriate respirator while near the contaminated air. The flux used for leaded solder is a heavy particle that doesn't rise up as much when heated and can be handled safely with only fume extractors. There's several other issues with lead-free solder that leaded solder does not have such as crystalline growths amongst a variety of other latent defects that can form well after cleaning and examination is completed.