Which of the following substances has been eliminated from residential building construction due to recognized health hazards?

The correct answer focuses on why lead has been eliminated or heavily restricted in residential building construction due to its well-documented health hazards. Lead exposure can cause serious health issues, particularly in children, leading to developmental delays, learning difficulties, and a range of other medical concerns. Due to these risks, regulations have been enacted that limit the use of lead-based paints and plumbing in construction processes.

While some of the other substances mentioned are also hazardous, they are not as universally banned or eliminated in the same way lead has been. For instance, asbestos has been heavily regulated due to its carcinogenic properties, but it hasn't been completely eliminated and can still be found in some older buildings in limited applications. Formaldehyde is recognized for its health risks, particularly in the form of off-gassing from certain building materials, and efforts have been made to limit its use, but it hasn't been entirely eradicated either. Lastly, radon is a naturally occurring gas that poses health risks as well, but it is typically managed through ventilation and mitigation measures rather than outright elimination from construction materials. Thus, lead's widespread restriction marks it as the substance most notably eliminated due to significant health risks associated with its use.