By Shannon Murphy

The purpose of evaluating materials under the six ANSI/NSF drinking water treatment unit (DWTU) standards is to ensure that materials in contact with drinking water don’t impart levels of extractable contaminants exceeding the Maximum Drinking Water Levels (MDWLs) specified in the standards for regulated and unregulated contaminants. Consumers expect that DWTUs will remove, and not add, contaminants Unfortunately, material requirements within the DWTU standards are often the most challenging component of the certification process. There are, however, ways to simplify this process and increase the odds of avoiding costly delays.

Minimum requirements
All six DWTU standards have minimum requirements for both systems and components. All systems shall meet the applicable requirements of Section 4 for materials, Section 5 for design and construction and Section 7 for literature, plus at least one performance claim as described in Section 6.

It’s critical then to understand the intricacies covered under the material requirements of the standards, as material acceptance is required for all products, be it systems or components.

Formulation disclosure
The first step in the process of material review is to have all wetted parts reviewed by a certifying agency. The parts list, as provided by the company seeking certification, details all materials in the product that are in contact with the drinking water. Parts of the water treatment device that don’t contact the drinking water, or add to the structural integrity of the system—like an aesthetic shroud—don’t need to have formulation disclosure.

One area of confusion on the wetted parts list is the exact formulation identification (ID) needed for the wetted material. The formulation ID has to be as descriptive as possible. For example, a wetted parts list stating a material and formulation ID as “EPDM 70 durometer” wouldn’t be adequate. Where a specific engineering diagram may reference the use of a 70 durometer o-ring, the wetted parts list must define the exact trade designation or formulation of the 70 durometer o-ring.

Minimum material requirements
Complete formulation information is required on any material not certified as specifically compliant with the sections of the U.S. Code of Federal Regulations, Title 21, Food and Drugs (Title 21 CFR), as listed in the standards. The standards only list wax and mineral oil lubricants, ion exchange resins, substances generally recognized as safe (GRAS) used in accordance with any conditions of the code, and solvents that may be considered for solvent bonding. Therefore, all housing materials, tubing, o-rings and gaskets, media other than specified ion exchange resins, storage containers and other parts are required to be evaluated first by the material formulation review process.

Formulation information required includes chemical identity of each ingredient in the material, its proportion by weight, supplier(s) of the ingredient, documentation regarding health effects concerns of each ingredient and documentation regarding health effects suitability of each ingredient for use in a potable water contact material. The ingredient and/or material supplier generally meets the latter two requirements using a Title 21 CFR citation or certification.

What is 21 CFR?
Title 21 CFR provides documentation regarding health effects’ concerns of the ingredient, and documentation regarding suitability of that ingredient as defined by the U.S. Food and Drug Administration (FDA).

CFR is a codification of the general and permanent rules published in the Federal Register by the executive departments and agencies of the federal government. The CFR is divided into 50 titles, which represent broad areas subject to federal regulation. Each title is divided into chapters, which usually bear the name of the issuing agency. Each chapter is further subdivided into parts covering specific regulatory areas. Large parts may be subdivided into subparts. All parts are organized in sections, and most citations to the CFR will be provided at the section level—21 CFR is then Title 21 of the Code of Federal Regulations. This document specifies what ingredients and materials can be in contact with food, and under what end-use conditions these ingredients/materials may contact food.

Making it compliant
To be considered compliant with 21 CFR, the end material (polymer + additives) must meet both the ingredient and testing requirements specified within 21 CFR. The material needs to be composed of ingredients, which are found within 21 CFR and meet any requirements associated with each of the ingredients. Simply having all the ingredients of a formulation found in 21 CFR doesn’t make the material compliant. The end material must also be tested according to the applicable testing requirements found within 21 CFR. For instance, a polypropylene material is generally made up of polypropylene resin, antioxidants, colorants and possibly other additives. All these ingredients must be found within an applicable 21 CFR reference and meet all requirements. For example, 175.300 is a section for coatings. If an ingredient is found within 175.300 and the end use of the material is meant for a pipe, this 21 CFR reference wouldn’t be applicable to the end use of the material. The main component of this material is the polypropylene resin. Polypropylene is found within 21 CFR 177.1520. At the end of this section of 21 CFR, there are testing requirements for polypropylene materials. The entire end-use material (polypropylene resin + antioxidants + colorants + other additives) must be tested according to the testing specification listed in 177.1520. This testing may be performed directly by the manufacturer or an external laboratory.

There are a number of online directories that can help you through the 21 CFR referencing. Two that are widely used include and

Options to 21 CFR
In addition to 21 CFR information, other data can be used to show that the material doesn’t present a health effects concern or contribute any contaminants to the drinking water.

Migration data
The FDA has a document referred to as “The Chemistry Guidelines Document” for submission of a Food Contact Notification. Within this document, the FDA outlines migration testing. This is used to show the level at which a specific ingredient migrates from the polymer under specific end-use conditions (i.e., the material is exposed to specific food stimulants at specific temperatures for a specific amount of time). This information can be used to show that an ingredient migrates out below 0.5 parts per billion (ppb) Threshold of Regulation level.

Legal letters of opinion
Formulators can obtain legal letters of opinion from firms specializing in direct and indirect food additives. These legal letters of opinion are documents that contain an evaluation of the material/ingredient/product of concern and provide an opinion based on sound scientific information. For the certification agencies to accept these legal letters of opinion, they not only need the legal letter of opinion itself, but also the evaluation data on which the letter of opinion was based. The FDA will often provide opinion letters on specific ingredients or the compliance of a material to 21 CFR.

Materials 21 CFR doesn’t cover
There are a few materials that won’t have a 21 CFR reference. Carbon is one of these materials. To approve carbon for use in a water treatment device, manufacturers should supply the American Water Works Association (AWWA) or FDA Food Codex reference. Both of these standards have testing requirements for carbon-based media. By stating that a carbon media complies with one of these references, the formulator is stating testing has been conducted on the media and results meet extraction requirements specified within the reference. If an AWWA or Food Codex reference can’t be obtained, then manufacturers should look to obtain other information provided such as extraction data or compliance to other national or international standards. If a formulator states compliance to another domestic or international standard, it’s best to have the test results available for review.

Other types of mined materials generally won’t have 21 CFR approvals. To approve these types of materials for use in a DWTU, a decompositional analysis on the material may be required. A decompositional analysis is a breakdown of what’s contained within the material. The material is crushed and analyzed to determine specific levels of metals and other contaminants.

Pigments & master batches
Pigments, thought easier to review for material acceptance, have their own special set of requirements. To evaluate a pigment or pigment master batch, the certification body needs to know what resin is used by the pigment and the specific letdown ratio—a measure of good mixing.

Ingredients contained within a pigment formulation also have limitations associated with 21 CFR. These limitations can be a percentage limitation or one based on resin. For example, ingredient A according to 21 CFR cannot exceed 1 percent of the material formulation and is approved only for use with materials complying with 177.1520. In the pigment formulation, ingredient A comprises 25 percent of the total formulation—higher than what’s approved. Therefore, to verify that the pigment meets the limitations described in 21 CFR, the certifying agency needs to know the letdown ratio to determine a final percentage of the ingredient in the end material.

Future changes
The requirement for material formulation disclosure is common across all drinking water related product standards around the world; however, there have been discussions recently within the standard’s development process regarding the necessity of formulation disclosure to have confidence in the acceptability of the product materials in contact with drinking water. One suggested alternative is a more comprehensive set of test parameters that would encompass the majority of possible contaminants that would otherwise have been identified during the formulation review process. The concern with this approach is having adequate test methodologies that could conduct such a broad range of testing. To do this properly would most certainly result in higher test fees, and perhaps more time consuming than gathering and reviewing formulations. A second suggestion also under review is reduced formulation submittals, particularly for those materials common in the DWTU industry. Look for updates in future articles as these discussions lead to possible changes in DWTU standards.

The drinking water treatment unit industry continues to prosper, meeting the needs of the consumer for improved water quality. While demonstration of performance claims is clearly the most obvious reason companies and their buyers seek independent testing and certification, there are related requirements also of significant benefit. Material acceptability is one of those, and one that can be very time consuming and frustrating. As more systems and components become tested and certified, this process will become more user friendly. Future changes to standards may enhance this even further. Meanwhile, companies knowledgeable of the necessary documentation, available options and process of submittal will find advantages in obtaining timely certification of their products.

About the author
Shannon Murphy is operations manager of the Drinking Water Treatment Unit program at NSF International in Ann Arbor, Mich. His bachelor’s degree in biology is from Concordia University in Montreal, Canada, and his master’s degree from Wayne State University in Detroit is in biology with an emphasis on limnology. Murphy can be contacted at (800) 673-6275, (734) 769-0109 (fax) or email: [email protected].

Additional information on this topic can be found at the NSF Toxicology Group website:


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