The effectiveness of the pollution prevention approach can be best illustrated by the sharp drop in which atmospheric pollutant?

The pollution prevention approach's effectiveness is exemplified by the significant reduction in lead levels in the atmosphere. Lead was a common additive in gasoline for many years, contributing to widespread air pollution and resulting in serious health issues, particularly affecting children's brain development.

The introduction of regulatory measures, such as the phase-out of leaded gasoline beginning in the 1970s and continuing through the 1990s, led to a dramatic decrease in atmospheric lead concentrations. This substantial legislative action marks a notable success in reducing a harmful pollutant through preventive measures, showcasing the power of regulatory frameworks in managing and mitigating air pollution.

While carbon monoxide, nitrogen oxides, and sulfur dioxide have also seen reductions due to various regulatory efforts, the specific and well-documented case of lead reduction illustrates the principles of pollution prevention most clearly.