By Richard H. Martin

Still waters run deep and rolling stones gather no moss (but do play rock concerts). In the pool and spa industry, NSF/ANSI Standard 50 certification is the measure of quality products as evidenced by the many states and codes that require the use of certified equipment in the design, construction and operation of pools and spas in North America. NSF/ANSI 50, covering pool and spa product testing, has been in existence for over 50 years. Over the decades, this standard has grown to include more breadth and depth. Although the ‘Stones’ may be rolling a bit more slowly these days, NSF/ANSI 50 has picked up steam, adding more and more product categories, detailed requirements and companies tested/certified to the criteria than ever before. There are now requirements for virtually every product used at recreational water facilities. There are over 30 different types of pool, spa and waterpark products in NSF/ANSI 50 per Table 1. Because there are so many different topics and only a few words in this article, I will focus on two of the newer categories of product addressed within NSF/ANSI 50: 1) water quality test devices and 2) chemicals and materials.

Water quality test devices
Products in this category include photometers, titration kits or dip strips used to measure a specific water quality parameter. NSF/ANSI 50 now has testing/certification requirements for the types of test kits indicated in Table 2. Testing and certification requirements for these products involve evaluation for accuracy, repeatability and shelf-life claims, as well as review of product use instructions, labeling and packaging. The standard requires testing of three separate products to each of the requirements.

Pool and spa materials and chemicals
NSF/ANSI 50 also includes criteria for evaluation of pool and spa chemicals and pool water materials, such as coatings, liners, etc. Requirements focus on material health safety criteria for high surface area products and chemicals that are dosed into pool, spa or waterpark waters. Specifically, formulation reviews, toxicology risk assessments and possible testing are required, along with review of product use instructions, labeling and packaging. Table 3 describes some of the common pool and spa chemicals.

Development and use of swimming pool treatment chemicals has enabled swimming to become a widely enjoyed form of exercise and leisure activity. In the US alone, there are over 10 million residential pools and more than 360 million people visit around 250,000 public swimming pools annually. While the primary focus for recreational water regulators and researchers has been hygiene and water quality (particularly on reducing or preventing infections caused by microbes and protozoa), new concerns have been raised regarding potential adverse health effects resulting from exposure to chemicals utilized in the treatment of swimming pools, hot tubs and spas.

In 2011, public officials made a presentation to the NSF/ANSI Standard 50 Recreational Water Facility Joint Committee (RWFJC)1 about their concerns with treatment materials and chemicals used in the pool and spa industry. The presentation by public officials centered on materials safety, contaminant assessment and performance testing for materials and chemicals. There was a heightened concern about the use of treatment chemicals that have not undergone any form of health effects evaluation or certification. Although a few types of pool and spa chemicals undergo a form of third-party review (typically certification under NSF/ANSI Standard 60), the officials noted that they had no readily available mechanism with which to properly evaluate the health risks of the pool/spa treatment chemicals. Based on this presentation, the RWFJC appointed a task group to develop a methodology for evaluating treatment chemicals used in the pool and spa industry for toxicity, chemical leachate, performance, efficacy and combined effects.

Since its first meeting in 2012, the RWFJC task group agreed initial focus would be on material health safety before investing focus on the content verification and performance assessment. Accordingly, the group has examined various approaches toward evaluating the toxicity of swimming pool materials and chemicals, including evaluation under NSF/ANSI Standard 61 for materials like coatings and liners, use of NSF/ANSI Standard 60 as well as methods used by US EPA Office of Pesticide programs. It was determined by the task group that NSF/ANSI 60 does not adequately address health effects that may be associated with dermal and inhalation exposures occurring from pool/spa uses since only oral exposure is considered under that standard. Additionally, the drinking water limits set forth in NSF/ANSI 60 are based on the assumption of consuming two liters of water per day, which greatly exceeds expected oral exposure resulting from pool or spa uses. In order to address some of the deficiencies in using NSF/ANSI 60 to assess swimming pool treatment chemicals, the task group contacted the US EPA Office of Pesticides and was given a presentation on the methods used by the US EPA in the evaluation of swimming pool antimicrobial products. Part of the US EPA method provided to the task group included various assumptions and equations that may be used to estimate dermal, oral and inhalation exposure to chemicals dosed into the pool water.

The RWFJC task group identified several challenges to the evaluation of the toxicity of pool treatment chemicals, among them, how to address byproducts produced through the reaction of the treatment chemical with other constituents of the treated pool water, as well as the potential accumulation of a treatment chemical or contaminants in the pool water due to multiple dosages over time. These challenges are compounded by the variability of pool-specific parameters, including individual pool water chemistry, variability in recirculation rates, different filtration rates/types, water replacement and splash-out rates. With the goal of developing a toxicological review process for swimming pool treatment chemicals that is both effective and timely, the RWFJC is first developing a simplified approach that consists of evaluating the treatment chemicals and contaminants contained in the finished product itself when dosed into the swimming pool at a maximum dose rate.

The currently utilized toxicology evaluation procedure for swimming pool chemicals borrows heavily from swimming pool treatment chemical exposure approaches used by the US EPA Office of Pesticides as well as the toxicological evaluation procedures set forth in Annex A of both NSF/ANSI Standards 60 and 61. The new procedure is briefly outlined below; however, it is important to note that this currently represents the latest procedure and is subject to change:

  • The pool chemical manufacturer must provide detailed product formulation information.
  • The maximum recommended dose rate of the product must be provided.
  • Based on the formulation information and label or use instructions, the concentration of each swimming pool treatment chemical (or contaminant) is then calculated.
  • Any chemical constituent (or contaminant) in the product formulation that has a concentration in the swimming pool water of ≤ 10 µg/L when dosed at the maximum recommended dose does not require further toxicology evaluation. This threshold value does not apply to any substance for which available toxicity data and sound scientific judgment indicate a significantly increased risk for an adverse health effect at a swimming pool water concentration at or below 10 µg/L.
  • For chemical constituents (or contaminants) with concentrations in the swimming pool water that exceed 10 µg/L at or below the maximum recommended dose, an exposure assessment is then performed utilizing the exposure assumptions and equations obtained from US EPA Office of Pesticides. The exposure assessment does account for dermal and inhalation routes of exposure in addition to oral exposure.
  • Following the determination of exposure levels for the chemical constituents (or contaminants), the acceptability of such exposure levels may be evaluated by using a published peer-reviewed risk assessment value for the specific chemical in question or a risk assessment may be conducted by the reviewing toxicologist utilizing an approach similar to the method set forth in Annex A of both NSF/ANSI Standard 60 and Standard 61.

The toxicology evaluation procedure outlined above is being used by NSF and is being reviewed by members of the RWFJC task group and toxicologists at NSF International. The task group will present more information to the NSF/ANSI Standard 50 Recreational Water Facility Joint Committee at the September 2014 annual meeting. After the presentation and other technical reviews, the revised requirements will be balloted for inclusion in NSF/ANSI 50.

While the current focus of the RWFJC task group is creating and balloting the methodology to assess the toxicity of individual chemicals, future work by the task group includes establishing methods for chemical dosing and leachate extraction testing in a manner similar to NSF/ANSI 60. Another future endeavor of the task group is to develop methods for the assessment of functionality and performance claims of pool treatment chemicals. Lastly, the task group intends to investigate methods to assess the safety of chemicals being used in conjunction with other chemicals under certain pool/spa conditions.

If you are interested in participating in the NSF Standard 50 Recreational Water Facilities Joint Committee Task Group on Chemicals and Materials, please contact Mindy Costello at [email protected] for more information.


  1. The RWFJC is composed of three equal voting membership groups of 11 persons each representing the following sectors: public health (such as the CDC and state and county public health inspectors and administrators), product manufacturers (such as makers of pumps, filters, UV systems, etc.) and end users (such as facility designers, facility operators, trade association members, etc.).

About the author
Richard Martin is a Senior Business Development Manager with NSF International. With 20 years of NSF experience managing various business areas, including programs related to NSF/ANSI 14, NSF/ANSI 61 and NSF/ANSI 50, he brings tremendous value to his current position through his wealth of technical knowledge, regulatory information, historical perspective and industry contacts. Martin may be contacted at [email protected] or (734) 769-5346 for additional information.


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