Other advantages to bismuth include: more uniformly distributed because of its similar density to iron; more environmentally friendly, as compared to lead; still weldable.
For paste solders, bismuth/tin/silver had the lowest impact scores among the lead-free alternatives in every category except non-renewable resource consumption.
Metallic lead that results from the roasting and blast furnace processes still contains significant contaminants of arsenic, antimony, bismuth, zinc, copper, silver, and gold.