What is the MCL for Total Trihalomethanes (TTHMs)?

The maximum contaminant level (MCL) for Total Trihalomethanes (TTHMs) is set at 80 parts per billion (ppb). This standard is established by the Environmental Protection Agency (EPA) to control these potentially harmful compounds that can form when chlorine or other disinfectants used in water treatment react with organic matter present in the source water.

TTHMs are significant because they are linked to various health risks, including potential impacts on the liver, kidneys, and central nervous system, as well as potential carcinogenic effects with long-term exposure. Thus, maintaining TTHM levels at or below the MCL is critical in ensuring drinking water safety and protecting public health.

Understanding the appropriate units for measuring contaminants is also crucial; in this case, the use of parts per billion (ppb) is standard for such low concentrations. This makes options measured in parts per million (ppm) inappropriate for this MCL. With this context, the choice reflecting the correct MCL of 80 ppb stands as the right answer.