Under the primary drinking water regulations, which MCL applies to fluoride?

The maximum contaminant level (MCL) for fluoride under the primary drinking water regulations is established at 4.0 mg/L. This standard is set to protect public health, as excessive fluoride in drinking water can lead to health issues such as dental fluorosis or skeletal fluorosis. The U.S. Environmental Protection Agency (EPA) has conducted assessments to determine safe levels of fluoride to minimize health risks while considering its benefits in reducing dental cavities.

The MCL is a crucial regulatory limit that must be adhered to by public water systems to ensure safe drinking water. While some other levels may be referenced in different contexts or for other substances, the specific MCL for fluoride, based on current regulations and health evaluations, is indeed 4.0 mg/L.