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Use of Borates in Swimming Pools: Consideration of Health Effects

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Presentation on theme: "Use of Borates in Swimming Pools: Consideration of Health Effects"— Presentation transcript:

1 Use of Borates in Swimming Pools: Consideration of Health Effects
Kevin Cox Senior Research Toxicologist NSF International

2 Boric Acid and Sodium borate
Boric Acid (and Sodium Borate salts) Active ingredients in insecticides, herbicides, algaecides, fungicides and wood and material preservatives Used in cosmetics, pharmaceuticals, water treatment chemicals Property Boric Acid Borax Borax Pentahydrate Anhydrous Borax Structure CAS# Chemical Formula H3BO3 Na2B4O7 10 H20 Na2B4O7  5 H20 Na2B4O7

3 Use in Swimming Pools Boric acid is commonly used as a pH buffer in pools Increases capacity of the water to resist changes in pH Boric acid is a Lewis acid (acquires OH- from water) At typical pH levels in pools, boric acid will be the primary form Other promoted functionalities of boron Algaecide, corrosion inhibition, protection against hypochlorite photolysis, adding tint or sparkle to water, improving water “feel” Sodium borate salts may be used as substitutes for boric acid Operators must be careful to add appropriate levels of boron based on the type of boron product used (e.g. boric acid v. borax)

4 Toxicity Profile of Boron
Absorption/Distribution/Metabolism/Excretion Readily absorbed from GI tract but poorly absorbed through skin Within the body, exists as undissociated boric acid Limited human toxicity data exists for boron Lethal doses range from 15 to 20 grams (adult), 5 to 6 g (child) Animal Studies Key toxicity findings reported in animal studies have been reproductive and developmental effects Chronic studies did not report any increase in tumors while available genetic toxicity studies were negative “Not likely to be carcinogenic to humans” per U.S. EPA guidelines

5 Organizational Assessments of Boron
Agency/Organization Year Numerical Risk Value Basis U.S. Environmental Protection Agency (U.S. EPA) – Integrated Risk Information System (IRIS) 2004 0.2 mg/kg-day (oral RfD) Used BMDL5 of 10.3 mg/kg-day based on reduced fetal weights reported from a developmental study in rats. Applied a UF of 66. U.S. Environmental Protection Agency (U.S. EPA) 2008 5 mg/L (lifetime health advisory for drinking water) Used BMDL5 of 10.3 mg/kg-day based on reduced fetal weights reported from a developmental study in rats. Applied a UF of 66 and a source contribution of 80%. World Health Organization (WHO) 2009 2.4 mg/L (drinking water limit) Used BMDL5 of 10.3 mg/kg-day based on reduced fetal weights reported from a developmental study in rats. Applied a UF of 60 and 40% source allocation. Agency for Toxic Substances and Disease Registry (ATSDR) 2010 0.2 mg/kg-day (intermediate MRL) Used BMDL5 of 10.3 mg/kg-day based on reduced fetal weights reported from a developmental study in rats. Applied a UF of 66.

6 U.S. EPA FIFRA Assessment (2008)
U.S. EPA evaluated the use of boron in swimming pools as part of FIFRA regulatory requirements U.S. EPA evaluated each specific boron use by assessing the margin of exposure (MOE) A NOAEL of 8.8 mg/kg-day from a chronic toxicity in dogs was divided by estimated exposures to determine the MOE The Level of Concern (LOC) was set at 100 For use of boron in swimming pools, application rates above 240 mg/L (as Borax Pentahydrate) resulted in MOE values that were below the LOC It was recommended that end uses that exceeded 240 mg/L (as Borax Pentahydrate) be revised Equivalent to 35 mg/L as boron

7 U.S. EPA FIFRA Assessment (2015)
In 2015, U.S. EPA re-evaluated the use of boron in swimming pools as part of requirements under FIFRA Again, U.S. EPA evaluated each specific boron use by assessing the margin of exposure (MOE) A NOAEL of 8.8 mg/kg-day from a chronic toxicity in dogs was divided by estimated exposures to determine the MOE The Level of Concern (LOC) was set at 100 Using updated swimming pool exposures and a swimming pool concentration of 35 mg/L (as boron), the U.S EPA found exposures to be acceptable for children (6<11), children (11<16) and adults

8 NSF Standard 50 Assessment
As concentrations of mg/L (as boron) are commonly recommended in products, use of boron was assessed using methods of Annex R of NSF/Standard 50 NSF assessed both 35 mg/L and 50 mg/L use rates (as boron) for children and adults U.S. EPA IRIS chronic oral reference dose of 0.2 mg/kg- day was used to assess acute and chronic exposures Chronic exposures were assessed against the RfD adjusted to account for other sources of boron exposure The results indicated that application rates of 35 mg/L and 50 mg/L (as boron) meet the requirements of NSF 50

9 Summary Increasing concern about exposures to chemicals in daily lives
Boron has demonstrated both reproductive and developmental toxicity in animals following oral exposure U.S. EPA in both 2008 and 2015 has recommended a swimming pool concentration limit of 35 mg/L (as boron) These limits were based on the toxicity observed in laboratory animals Assessment under Annex R found mg/L application to be acceptable As pool application rates have been established based on health effects criteria, it is important to monitor levels of boron in pools

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