Which statement about NAAQS is true?

• A. NAAQS include primary standards for health and secondary standards for welfare.
• B. NAAQS apply only to water.
• C. NAAQS are optional guidelines.
• D. NAAQS apply to indoor air only.

Answer: (A)

NAAQS are set to protect public health and public welfare from outdoor air pollution. They include two kinds of standards: primary standards, which are designed to protect human health (including sensitive groups like children and the elderly), and secondary standards, which are designed to protect public welfare—things like crops, vegetation, animals, visibility, buildings, and climate. This dual structure is why the statement is true: NAAQS include primary standards for health and secondary standards for welfare.

They aren’t about water quality, so applying them to water would be inaccurate. They aren’t optional guidelines; they are mandatory standards. And they address outdoor ambient air, not indoor air only.