What is the difference between primary and secondary drinking water standards?

Primary drinking water standards are established to protect public health by setting maximum contaminant levels (MCLs) for substances that pose a risk if consumed. These standards are legally enforceable and specifically target contaminants that can adversely affect human health, such as lead, mercury, and certain bacteria.

On the other hand, secondary drinking water standards are not legally enforceable. They focus on aesthetic qualities such as taste, odor, and color, addressing concerns that may affect the acceptability of drinking water but not necessarily its safety. Examples include the presence of chlorine or sulfur, which might not pose a health risk but can make water unpalatable.

This distinction underscores the critical nature of primary standards in safeguarding health, while secondary standards are aimed at ensuring that the water is pleasant to drink and use. This is why the answer that states primary standards protect health, whereas secondary standards focus on aesthetic concerns is accurate.