Decades ago, most of the paint used in the US was lead-based because it was cheap, long lasting, and widely available. When scientists recognized that this was polluting the air with toxic lead, laws banned lead-based paint, and the paint industry developed more cost-effective paints that do not contain lead.
What was most likely the type of problem lead-based paint had that was solved by using paints without lead?

A. limited availability
B. ineffective for most uses
C. lack of durability
D. health risk to users