By Rick Andrew
Manganese has long been recognized as an aesthetic drinking water contaminant due to its potential for black staining—including fixtures and laundry—and its bitter metallic taste. USEPA has recognized this issue by establishing a Secondary Maximum Contaminant Level (SMCL) in drinking water. This aesthetic contaminant status and SMCL have in turn been reflected in requirements for contaminant reduction for manganese being established in NSF/ANSI 42.
In 2019, a new development in the status of manganese as a health contaminant occurred. Health Canada promulgated a new Maximum Acceptable Concentration (MAC) in drinking water. This level is based on specific health effects noted by Health Canada, including effects on neurological development and behavior; as well as deficits in memory, attention, and motor skills.
This development of a new health effects level in drinking water for manganese led to activity to develop requirements for POU and POE systems with health claims for manganese reduction.
Health Effects Claims
Health Canada teamed up with the Water Quality Association (WQA) to develop WQA ORD1901 – Harmonized Product Requirements for Drinking Water Treatment Units that make Manganese Performance Claims, published in 2019. This document establishes requirements for cation exchange water softeners, water filters utilizing mechanical filtration, POU reverse osmosis (RO) systems, and distillation systems to establish health claims for manganese reduction.
The requirements in ORD1901 were intentionally harmonized with the requirements of NSF/ANSI 44, 53, 58, and 62. The test methods for contaminant reduction in ORD1901 are consistent with the test methods in the corresponding NSF/ANSI standards. So, water softeners are tested according to the typical regime for contaminant reduction under NSF/ANSI 44, filters utilizing mechanical filtration technology are tested according to the usual methodology of NSF/ANSI 53, POU RO systems according to the contaminant reduction test protocol of NSF/ANSI 58, and distillers according to the methods in NSF/ANSI 62.
The average influent challenge concentration of manganese in ORD1901 was established at 0.9 – 1.1 mg/L. The maximum product water concentration was established at 0.05 mg/L, which is the aesthetic threshold as promulgated by USEPA in their SMCL. The reason for this selection is that the Health Canada MAC is higher than the USEPA SMCL at 1.2 mg/L. It was decided that consumers would not be satisfied with a treatment system that protects them at a health effects level but still produces water with aesthetic issues associated with manganese. So, the lower SMCL level was selected as the ORD1901 maximum product water concentration.
For a summary of the various drinking water levels for manganese developed in regulations and standards, please see Figure 1.
The Extraction Level for Manganese
One other consideration with ORD1901 was the Total Allowable Concentration (TAC) of manganese allowed in extraction testing. Typically under the NSF/ANSI DWTU Standards, the TAC is established in NSF/ANSI 600 Health Effects Evaluation and Criteria for Chemicals in Drinking Water. NSF/ANSI 600 established a TAC for manganese of 0.3 mg/L. This value was calculated through a toxicological risk assessment conducted in 1995, derived from the oral reference dose on the USEPA IRIS database. A reference dose is generally an estimate of a daily exposure of a contaminant to humans throughout their lifetime that is likely to be without adverse effects.
However, this value of 0.3 mg/L is higher than the Health Canada MAC of 0.12 mg/L. Therefore, it was decided that the manganese TAC, for the purposes of ORD1901, would be 0.1 mg/L to be consistent with the Health Canada MAC.
When ORD1901 was developed, it was intended to be a temporary tool allowing for this important evaluation until a more permanent, consensus-based standards solution could be developed. Keeping this in mind, the subject was discussed at the May 2022 meeting of the NSF Joint Committee on Drinking Water Treatment Units.
The Committee formed a task group to investigate the potential to add health-based claims for manganese reduction to NSF/ANSI 44, 53, 58, and 62. The task group met in mid-June and discussed the situational background and the various work done regarding testing of specific technologies for manganese reduction. After a review of this previous work and findings, the task group decided to focus on adding health claims for manganese reduction to NSF/ANSI 44 and 53, while tabling NSF/ANSI 58 and 62 for potential future work. They also agreed to revisit the aesthetic manganese reduction under NSF/ANSI 42 to assure that the logic of the requirements is consistent with the logic for the health claim requirements under the other standards.
Continuous Improvement Serving Multiple Stakeholders
The current efforts of the NSF Joint Committee on Drinking Water Treatment Units and the task group are reflective of their mandate to serve the needs of three primary stakeholder constituencies: product end users, regulators, and manufacturers. In this case, Health Canada, an essential regulatory stakeholder, has a need to develop standards that address manganese as a health contaminant. The manufacturer and end user constituencies have come together to provide expertise regarding product technology and capabilities, which is melded altogether to develop meaningful, science based, rigorous criteria for establishing the ability of drinking water treatment technologies to treat manganese as a health contaminant.
1. Guidelines for Canadian Drinking Water Quality – Summary Tables – Canada.ca (https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/water-quality/guidelines-canadian-drinking-water-quality-summary-table.html)
About the author
Rick Andrew is NSF’s Director of Global Business Development–Water Systems. Previously, he served as General Manager of NSF’s Drinking Water Treatment Units (POU/POE), ERS (Protocols) and Biosafety Cabinetry Programs. Andrew has a Bachelor’s Degree in chemistry and an MBA from the University of Michigan. He can be reached at (800) NSF-MARK or email: Andrew@nsf.org