By Rick Andrew

Imagine this: You’ve just purchased an incredible new water treatment product. It looks great, delivers great looking, great tasting water and reduces more contaminants more effectively than any other water treatment system you’ve ever seen.

Unbeknownst to you, some of the materials used to manufacture this new product are unsafe. In fact, one is not intended (by the material formulator) for use in contact with drinking water—this material is made using processes known to create some carcinogenic by-products that can leach from the material into drinking water. There is a second polymer material that releases unhealthy monomer molecules due to the molding conditions used to shape it to fit into the product. Because of the use of these materials and processes in making the product, the product releases potentially toxic contaminants into the very drinking water that it treats.

How do you feel about that new water treatment product now? Somehow, the great look of the product, the great taste of the water and the contaminant reduction capabilities of the system no longer seem quite so attractive. Although the product may take some contaminants out, it is putting others that may be equally as bad—or worse!—back in.

Material safety: necessary for all materials in contact with drinking water
As the example above demonstrates, material safety is a baseline necessity for all water treatment products. All the wonderful contaminant reduction capabilities and other features lose their value if the materials in contact with water are not safe. For this reason, conformance to the material safety requirements in the NSF/ANSI Drinking Water Treatment Unit (DWTU) Standards is required for all products—systems, components, plumbed-in, pour-through batch—you name it, material safety is required.

Three steps to establish material safety
There are three steps required to establish material safety:

  1. Formulation review
  2. Extraction testing
  3. Toxicological review of extraction test results

The purpose of the formulation review is to determine the potential of the material to leach specific contaminants into the water being treated. The theory is relatively simple: What goes in may come back out again. A formulation review is required for all materials in contact with product water. Materials in a drain line, or on the brine side of a water softener or reverse osmosis system, are not in contact with product water and are exempted from this requirement.

In practice, product certifiers can maintain some form of database of material formulations. It is possible that more than one manufacturer may use the same material for a water contact application. Certifiers may elect to require that a material formulation be disclosed only once, regardless of how many manufacturers are using the material.

Once all of the formulations for materials in contact with water have been disclosed, a trained and qualified professional toxicologist can make an assessment of potential contaminants that may leach from the water contact materials. This assessment, when conducted properly, will include such potential concerns as monomers leaching from polymers, leaching of specific ingredients, leaching of impurities from various ingredients, leaching of by-products resulting from the material formulation process and others.

The list of potential contaminants developed by a toxicologist, coupled with a list of required analytes included in the Standard, serves as a guide to the laboratory conducting the extraction test. This guide is necessary for the laboratory to implement proper testing. When it comes to analytical chemistry, the reality is that you won’t find it if you don’t look for it. And the whole idea of extraction testing is to find any contaminants that could potentially be present in treated water.

Extraction testing part I: exposure and analysis
The first step in conducting an extraction test is known as the exposure. Exposure is just that—putting water in contact with the test product to give contaminants the opportunity to leach out, if they are inclined to do so.

The NSF/ANSI DWTU Standards specify the chemistry of this water, in order to provide for consistent results. The chemistry of the water can impact how certain contaminants may or may not leach out. These requirements of the NSF/ANSI DWTU Standards are included in Figure 1.

Products not connected to the plumbing are exposed in their normal usage mode. Those products connected to plumbing are exposed under pressure at 50 psig initial inlet static pressure. A test stand is used to deliver the water referenced in Figure 1. A photo of such a test stand, including a hypothetical test product consisting of a pipe with two end caps, shown in Figure 2.

The exposure procedure consists of flushing and conditioning the product per the manufacturer’s instructions, repeatedly exposing it to the water referenced in Figure 1 and then collecting samples to be mixed or ‘composited’ together for analysis. Details of this exposure procedure are included in Figure 3.

Systems that contain adsorptive or absorptive media, such as carbon, must be tested with and without the media. This approach of testing without the media, in addition to the normal configuration of the product, allows for an evaluation of potential contaminant leaching if consumers do not replace their media as instructed or if they elect to remove the media and leave the housing in place.

The exposure water samples of the product with and without the media are then routed to the laboratory for analysis according to the list of potential contaminants prepared by the toxicologist.

Extraction testing part II: toxicological evaluation
Once the analysis of the exposure water has been completed, the results are reviewed by a trained, professional toxicologist to determine if any contaminants have been detected at concentrations that exceed levels of toxicological concern. For some contaminants, this determination is very simple. The simple ones include contaminants that have a maximum contaminant level (MCL) promulgated by U.S. EPA. There are also some contaminants that have a maximum contaminant concentration (MCC) that is derived from other regulatory agencies, such as Health Canada.

However, for some other contaminants, the assessment of toxicological concern is not so simple. These contaminants may not be regulated by government agencies, so there are no established concentrations of concern. A simple approach might be to ignore them, but this approach does not address risk management and is not permitted. The NSF/ANSI DWTU Standards require that any contaminants detected be evaluated. The Standards require that a maximum drinking water level (MDWL) be developed for these contaminants, using risk assessment procedures established in NSF/ANSI 61.

These risk assessment procedures include review and analysis of toxicological studies done on animals, as well as epidemiological statistical exposure and response evaluations observed in humans. Depending on the specific contaminant, there may be many of these studies available for review and analysis, or none at all. Typically, these studies have been performed on contaminants that are used for industrial purposes and/or have been detected in the environment. If a contaminant is not widely used and has not been an issue for the environment, there may be no need for toxicological studies to be performed on it. In cases where little relevant toxicological research has been performed, the risk assessment procedures direct a conservative approach of establishing a very low MDWL of 3 µg/L.

Having a capable laboratory and expert toxicology staff is critical to performing extraction tests correctly. If a laboratory has limited capabilities, such as limited mass spectral libraries, the laboratory may not be able to detect, identify or quantify contaminants in the exposure water properly. If expert toxicologists are not involved, proper MDWL values cannot be assigned for certain contaminants. Either one of these missing critical functions can lead to an improper assessment of risk.

Material safety: the bottom line
Much of the focus of the Water Matters column is on contaminant reduction testing. After all, contaminant reduction is the whole purpose of residential drinking water treatment products. But underlying all of the great contaminant reduction capabilities of these products is a fundamental necessity for safe materials. Without safe materials, a water treatment system can end up doing more harm than good.

Keeping in mind this necessity for safe materials, I devoted this column to the complicated details of establishing material safety through formulation review, extraction testing and toxicological review. Toxicological evaluations and material formulation reviews are not the day-to-day focus of most water treatment professionals, but it’s good to step back and understand this fundamental building block of conformance to the NSF/ANSI DWTU Standards.

About the author
Rick Andrew has been with NSF International for over six years, working with certification of residential drinking water products. He has been the Technical Manager of the Drinking Water Treatment Units Program for over three years. His previous experience was in the area of analytical and environmental chemistry consulting. Andrew has a bachelor’s degree in chemistry and an MBA from the University of Michigan. He can be reached at 1-800-NSF-MARK or email: Andrew@nsf.org.

 

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