Question

why was 1990 an important year regarding air quality? the united states took first steps to keep the air clean. the united states created the environmental protection agency. modifications and improvements were made to the clean air act. funding was established under the clean air act to study air pollution.

Explanation:

In 1990, the United States made significant modifications and improvements to the Clean Air Act to address air - quality issues more effectively. The first steps to keep air clean were earlier, the EPA was created in 1970, and funding for air - pollution study under the Clean Air Act was not specifically established in 1990 as its main significance.

Answer:

Modifications and improvements were made to the Clean Air Act.