The abbreviation MCL (Maximum Contaminant Level) is indeed one of the most commonly used regulatory standards for contaminants in drinking water in the U.S., as established by the Environmental Protection Agency (EPA). However, it's essential to understand that MCL values are specifically set for drinking water and may not be the most appropriate or applicable criterion for other water types like river water, sewage, or industrial wastewater.

Here’s a quick overview of relevant EPA terms to clarify their appropriate usage:

• MCL (Maximum Contaminant Level): This is the legal limit on the amount of a contaminant allowed in public drinking water systems. It’s designed to ensure the safety of drinking water for human health and is enforceable. The MCL is typically chosen based on balancing health risks, technical feasibility, and cost.
• MCLG (Maximum Contaminant Level Goal): This is a non-enforceable health goal that represents a level of a contaminant in drinking water at which no known or anticipated adverse health effects would occur. Unlike the MCL, the MCLG is solely based on health considerations without factoring in cost or feasibility. The MCL is usually set as close to the MCLG as possible, though MCLs can be less stringent due to practical and financial constraints.
• RSL (Regional Screening Level): RSLs are risk-based screening levels used in Superfund (contaminated site cleanup) evaluations, and they help determine if a more detailed investigation is needed. They’re more commonly applied to soil and groundwater contamination rather than direct drinking water standards.
• CMC (Criterion Maximum Concentration) and CCC (Criterion Continuous Concentration): These are water quality criteria related to aquatic life, not drinking water. CMC represents the highest concentration of a pollutant that aquatic life can be exposed to for a short period without harm, while CCC is the concentration that aquatic life can tolerate over a longer duration without harm.

Using MCLs for Other Water Types

MCLs are designed for human health protection in drinking water and may not be fully relevant for non-drinking water sources (e.g., rivers, lakes, sewage). For other water types, like rivers or sewage, the EPA and other environmental agencies often use water quality criteria or effluent standards tailored to protect aquatic life, human health through indirect exposure, and ecosystem health, rather than the MCL.

For example:

• Surface waters (like rivers) often have criteria based on the Clean Water Act, which may include standards to protect aquatic life and recreational uses.
• Wastewater or sewage discharges are typically regulated under the National Pollutant Discharge Elimination System (NPDES), which sets permit limits based on technology capabilities and water quality needs, not MCLs.

Summary

While MCLs are highly reliable and enforceable standards for drinking water safety, they are not a one-size-fits-all criterion for all water types. Instead, it’s often better to use the relevant criteria or standards tailored to the specific type of water (e.g., aquatic life criteria for rivers, effluent limits for sewage) to ensure accurate and appropriate environmental protection.

Thank you very much for your assistance and help Raghad Mouhamad.

MCL, or Maximum Contaminant Level, is a useful regulatory standard primarily for drinking water, as it represents the highest permissible concentration of a contaminant according to the EPA. However, using MCL as a universal indicator for all water types (e.g., river water, sewage) may not be appropriate. This is because MCLs are designed specifically for human health safety in drinking water and do not account for the ecological health or quality needs of other water sources. For instance, aquatic life criteria, such as CMC (Criterion Maximum Concentration) and CCC (Criterion Continuous Concentration), are tailored for environmental water bodies to protect ecosystems. Therefore, while MCL is reliable and cost-effective for drinking water, it should not be applied universally across all water types without considering the context and specific water quality standards.

Thank you Hasan Altawil.