Final answer:
The Clean Air Act of 1970 centered on addressing pollutants by setting national air quality standards for six criteria pollutants, making significant changes in the automotive industry, and establishing command-and-control regulations to enforce these standards. Later amendments in 1990 targeted sulfur dioxide emissions and introduced marketable permits to further enhance air quality.
Step-by-step explanation:
Most of the debate surrounding the Clean Air Act of 1970 was centered on the issue of pollutants and the establishment of national air quality standards to protect public health and the environment. The U.S. Environmental Protection Agency (EPA) set standards for six common air pollutants, known as criteria pollutants, which include carbon monoxide, ground-level ozone, nitrogen dioxide, sulfur dioxide, lead, and particulate matter. Ground-level ozone and particulate matter are considered the most widespread health threats. The 1970 Act also required significant reductions in vehicle emissions, leading to the inclusion of catalytic converters in cars and the transition to unleaded gasoline.
Furthermore, the Act introduced command-and-control regulation, which mandated industries and automakers to meet specific pollution standards within a given timeline. This approach has been pivotal in improving the U.S.'s air quality over the decades. Nevertheless, economists have identified certain difficulties with this type of regulation, hinting at its complexity and the challenges in implementation and flexibility.
Additionally, the 1990 amendments to the Act aimed to reduce sulfur dioxide emissions and address other environmental concerns such as acid rain, which was harming forests and buildings. The amendments involved the use of marketable permits to incentivize reduced emissions from electric power plants.