Which of the following describes the Environmental Protection Agency's main responsibility?

The Environmental Protection Agency (EPA) is primarily tasked with overseeing air and water pollution control. This responsibility encompasses enforcing laws and regulations that protect the environment and public health from pollutants in the air and water sources. The agency works on ensuring compliance with the Clean Air Act and the Clean Water Act, among other legislation.

In this context, while regulating pesticide usage in agriculture is a relevant responsibility of the EPA, it is not the organization's main focus. Waste disposal management in biotechnology labs falls under more specialized regulatory frameworks and is not a primary responsibility of the EPA. Conducting health research related to environmental factors, although a part of EPA activities, is more about assessing and managing risks rather than the main function of pollution control. Thus, the most accurate description of the EPA's main responsibility is in the realm of controlling pollution to safeguard public health and the environment.