What is the difference between NAAQS primary and secondary standards?

• A. Primary standards protect public welfare.
• B. Primary standards protect public health; secondary standards protect public welfare.
• C. Primary standards protect crops.
• D. Primary standards protect visibility.

Answer: (B)

NAAQS come in two types to protect different endpoints: health and welfare. Primary standards are set to protect public health, including sensitive groups like children, the elderly, and people with heart or lung conditions, from harmful levels of pollutants. Secondary standards are set to protect public welfare, which covers broader effects such as crops and vegetation, wildlife, property and climate, and also visibility and other aspects that affect daily living and the economy.

So the best choice says that primary standards guard human health while secondary standards guard welfare. In practice, the two sets of standards can be the same or different depending on the pollutant and its known effects, but the distinction lies in the protection goals: health vs welfare.