What differentiates maximum contaminant level (MCL) from a secondary maximum contaminant level (SMCL)?

The differentiation between maximum contaminant levels (MCLs) and secondary maximum contaminant levels (SMCLs) is fundamentally based on their intended purpose and implications for public health.

MCLs are established by the Environmental Protection Agency (EPA) to protect public health by limiting the levels of contaminants in drinking water that are known or expected to pose significant health risks. This means that MCLs are concerned with substances that can lead to acute or chronic health effects, including severe conditions such as cancer or reproductive issues.

On the other hand, SMCLs are primarily focused on the aesthetic aspects of water quality, such as taste, color, odor, and other non-health-related effects. While these contaminants may not pose serious health concerns, they can significantly affect consumer acceptance of drinking water. For instance, high levels of iron or manganese can lead to discoloration or metallic taste but are not typically associated with adverse health effects.

This clear distinction underscores that MCLs prioritize human health and safety, while SMCLs address more quality of life issues associated with water consumption. Recognizing this difference is crucial for understanding water quality regulations and their implications on public health and community well-being.