By Blake Stark

Everyone is familiar with chlorination of swimming pools. This is a long-standing practice that has been used for many years to help improve the safety of swimming pools and reduce the incidence of communicable diseases associated with swimming in them. In recent years, however, there has been a proliferation of new techniques to disinfect and treat swimming pool water to help make it safe and potentially use alternatives to chlorination in some cases. Some of these techniques include the use of chemical disinfectants and other types of chemicals to help treat the water. Have you ever wondered what type of safety evaluation has been performed to assess these types of chemicals? The NSF Joint Committee on Recreational Water Facilities has certainly wondered about this. As a result, they have developed criteria to assess the potential health risks associated with using some of these types of chemicals in the treatment of swimming pool water.

A document containing new testing and evaluation requirements for pool treatment chemicals is in the final stages of balloting and will be included in the next addition of NSF/ANSI Standard 50; Equipment for Pools, Spas, Hot Tubs and Other Recreational Water Facilities. The new document (which will become a new section of NSF/ANSI 50) was drafted by a task group that consisted of public health professionals, recreational water facility operators and treatment chemical manufacturers. The completed document will become the first NSF standard designed specifically for swimming pool treatment chemicals.

The Toxicology Review and Evaluation Procedures for Swimming Pool Treatment Chemicals are summarized below. At present, the inclusion of evaluation criteria for pool chemicals in NSF/ANSI 50 is focused primarily in the area of health effects. This is most important for those chemicals that are not covered by the scope of the US EPA Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) requirements such as disinfectants, algaecides and other biocides, which undergo a separate evaluation/registration through the US EPA Office of Pesticides. Disinfectants, algaecides and other biocides that are registered by the agency are not subject to the additional risk assessment criteria of the new NSF/ANSI 50 Annex; however, such chemicals would still be tested for contaminants.

While pool and spa disinfectants have been regulated by US EPA, there is a lack of regulations in the US that address the potential health effects for other types of pool chemicals. Some states have required pool chemicals to conform to the NSF standard for drinking water treatment chemicals, NSF/ANSI 60. The use of that standard to evaluate pool chemicals, however, is overly restrictive when assessing oral exposure and lacked the methodology to evaluate dermal and inhalation effects. The overall lack of an adequate method to assess the health effects of pool chemicals prompted public health officials to propose to the NSF/ANSI 50 committee the development of new criteria to assess pool and spa chemicals. A task group was formed in 2012 to develop the criteria and this group worked with chemical manufacturers, state agencies and officials with the US EPA Office of Pesticides to develop the new criteria.

Summary of the new toxicology review and evaluation procedures for swimming pool treatment chemicals:

  • Detailed product formulation information shall be obtained that allows for the identification of all unique chemical components of the product, as well as the concentrations of each component. Additionally, the maximum recommended dose rate of the product shall be provided.
  • Based on formulation information and label or use instructions, the concentration of each swimming pool treatment chemical (and/or contaminants) in the swimming pool water following dosing at the maximum recommended dose rate shall be calculated.
  • As an initial toxicity screening evaluation, any chemical constituent (or contaminant) in the product formulation that has a concentration in the swimming pool water of ≤ 10µg/L at the maximum recommended dose does not require further toxicology evaluation. This threshold value shall 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 10µg/L. All chemical constituents (or contaminants) that exceed the 10µg/L threshold at or below the maximum recommended dose require additional evaluation.
  • For chemical constituents (or contaminants) with concentrations in the swimming pool water that exceed 10µg/L at or below the maximum recommended dose, an exposure assessment shall be performed utilizing A New Standard for Pool Chemicals By Blake Stark Water Conditioning & Purification August 2015 equations and assumptions prescribed in the new standard.
  • Following the determination of exposure levels (in mg/ kg-day) for chemical constituents (or contaminants) with concentrations in the swimming pool water that exceed 10µg/L at or below the maximum recommended dose, the procedure defines several approaches that may be utilized to determine the acceptability of the calculated exposure.
  • A determination shall be made as to whether a published (publicly available in printed or electronic format) and peer-reviewed, quantitative risk assessment for the chronic exposure to the substance is available. When a quantitative risk assessment is available, the assessment and its corresponding reference dose shall be reviewed for their appropriateness in evaluating the human health risk of the swimming pool treatment chemical constituent (or contaminant).
  • As an alternative approach, the total allowable concentration (TAC) values as reported in NSF/ANSI Standard 60 (2013) and NSF/ANSI Standard 61 (2013) may be utilized if available for the specific chemical constituent (or contaminant) by converting the TAC value into a mg/kg-day rate by utilizing default body weight and drinking water consumption assumptions (70 kg and 2 L), respectively. The resulting mg/kg-day rate may be compared with the estimated exposure at the maximum recommended dose to determine acceptability
  • If a TAC value or other published risk assessment value is unavailable, a risk assessment for the specific chemical constituent (or contaminant) may be conducted in accordance with the procedures outlined. However, in lieu of determining a TAC value, the identified point of departure may be utilized to conduct a margin of exposure (MoE) analysis.
  • If a TAC value or other published risk assessment value is unavailable and there are insufficient toxicity data from which to perform a risk assessment, the chemical exposure cannot be assessed and presence of the chemical in the formulation is precluded at a concentration in the swimming pool water of greater than 10ug/L.

Raising the bar on safety in the pool
For years, NSF/ANSI 60 Drinking Water Treatment Chemicals–Health Effects has provided scientific criteria that is used and widely accepted to assess the safety of chemicals used to disinfect and otherwise treat drinking water. Now, thanks to the efforts of the NSF Joint Committee on Recreational Water Facilities, NSF/ANSI 50 includes analogous criteria to evaluate the safety of chemicals used in the treatment of swimming pool water. This development will help chemical manufacturers and distributors, public health officials, pool and waterpark operators and consumers be assured of safety for those enjoying a swim.

About the author
Blake Stark is NSF’s Business Unit Manager for Water Treatment Chemicals & Filtration Media. He has been with NSF for over 20 years, most of which has been in management of NSF’s treatment chemicals certification to NSF/ANSI 60. Stark has a Bachelor’s Degree in geology from Adrian College and an MBA from Walsh College (both in Michigan). He can be reached at (800) NSF-MARK or email: [email protected]