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Thread: How and why do borates suppress algae?

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    How and why do borates suppress algae?

    It seems conclusive that borates can be helpful in suppressing algae. Does anyone know how or why? Any theories?

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    Re: How and why do borates suppress algae?

    In the early patents on borates for pool use it was suggested that borates would lower CO2 levels in the water but this mechanism is not likely. Boron is both a necessary nutrient for plant and animal life and, in higher doses, a poison. It's use as a fungicide and algaecide is well documented in other industries, however.

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    Re: How and why do borates suppress algae?

    There is some speculation as to mechanisms in this document though nothing I would consider definitive. For example, it states the following:

    There is evidence in both in vitro and in vivo systems that boric acid has an affinity for cis-hydroxyl groups, and this may be the mechanism that explains the biological effects of boric acid. However, this attachment is known to be reversible and concentration dependent, responding to clearance mechanisms.

    and there was further info on the testicular effects seen in dogs and other animals from ingestion.
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    Re: How and why do borates suppress algae?

    Thank you very much for this citations.

    Can you help with the math of converting mg of boron compound/kg body weight to ppm?
    — AnnaK —

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    Re: How and why do borates suppress algae?

    50 ppm is parts-per-million which is essentially the same as milligrams per liter. So one liter (about a quart) of pool water has 50 mg of Boron (assuming the pool water has 50 ppm Borates -- the Borates measurement is actually in units of ppm Boron). The acute oral LD50 (lethal dose for 50% of the subjects) amount is 250-350 mg/kg of body weight. It looks like a level of 8.8 mg/kg had minimal effects, but higher amounts fed daily led to smaller testicles (in male dogs, obviously). 10 kg is 22 pounds so this is why I recommend that dogs not drink pool water containing borates on a daily basis (one liter of 50 ppm Borate water drunk by a 22 pound dog is 5 mg/kg). They shouldn't drink it anyway, but the borates would be the most harmful substance in the water in quantity (in SWG pools, the salt level might also be a problem).

    Richard
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    Re: How and why do borates suppress algae?

    Borax. Sodium Tetraborate decahydrate (Na2B4O7.10H2O)

    To convert sodium tetraborate decahydrate into the equivalent boron (B) content, multiply by 0.1134.

    Ingestion: Products containing Borax are not intended for ingestion. Borax has a low acute toxicity. Small amounts (e.g., a teaspoon) swallowed accidentally are not likely to cause effects; swallowing amounts larger than that may cause gastrointestinal symptoms.

    Note to physicians: Observation only is required for adult ingestion in the range of 4-8 grams of Borax.

    The World Health Organization (WHO) acceptable range of intake is 1-13 mg boron/day for adults.

    Many studies that have shown therapeutic or preventative effects of boron used about 3 mg per day. With a safe upper limit of 0.16mg. per Kg. of body mass per day. For a 150 lb. (68 Kg) person, that would be about 10.88 mg. per day.

    For a 22 lb dog that would be 1.6 mg. 0.032 liters (1.0 ounces) of 50 ppm borates per day for a safe upper limit. Using 1.6 mg/kg of body mass per day as a maximum safety level = 16 mg = .32 liters (10 fluid ounces) at 50 ppm.

    To get 10 mg of boron a day from drinking water containing 50 ppm, you would need to drink 0.2 liters or 6.76 fluid ounces per day, or just under one cup.

    The average US diet contains about 1.5 mg of boron per day.

    Over 95% of absorbed boron is excreted by the kidneys, and its biological half-life is less than one day.

    Studies of developmental effects of boron have been carried out in mice, rats, and rabbits, and have shown that there are developmental changes. The no-observed-adverse-effect-level (NOAEL) for boric acid was found to be equal to or greater than 125 mg/kg for rabbits and 450 mg/kg for mice. In the rat, a lowest-observed-adverse-effect-level (LOAEL) of 78 mg/kg resulted in decreased fetal weight.

    Doses, including dietary intake for the workers at the high end of the exposure range, averaged 0.38 mg boron/kg of body weight per day = (25 mg. for a 150 lb person) with no major adverse health effects.

    The Tolerable Upper Intake Level for boron for adults is 20 mg/day. For adults, the amount of boron commonly provided in a single dietary boron supplement is 0.15 mg but may be as high as 40 mg.

    The observations which were studied suggest that boron intake at the level of 5-6 mg./day is consistent with prevention of arthritis.

    Some experts believe 1.5 to 3.0 milligrams of boron should be included in the daily diet.

    One study shows that when human consumption of boron is less than 2 milligrams per day that there is a 20 percent increased risk of arthritis. When the diet provides 5-6 milligrams of boron per day, the prevalence of arthritis is lower than average. A 9-10 milligrams per day boron intake may be able to virtually eradicate common forms of arthritis.

    Researchers have calculated that an upper exposure dose of 18 milligrams of boron per day is safe. The American diet provides about 1.5 milligrams of boron, so water can provide up to 16.5 milligrams per day without toxicity.

    Other researchers have determined that up to 13 milligrams of boron per day are safe.

    Assuming a LD50 of 250mg/kg of body mass, a 150 lb person would need to consume 17grams to have a 50% chance of dying. To get that much a person would need to consume about 341 liters or about 90 gallons of water containing 50 ppm.

    The minimum lethal dose of boron for humans has not been established although single doses of 18 to 20 grams in adults have been fatal.

    Algal toxicity: Green algae, Scenedesmus subspicatus 96-hr EC10 = 24 mg B/L* = 24 ppm.

    Conclusions: Recommended doses for boron are 1-10 mg per day for an adult with an upper limit of 20 mg per day. Use in pools should be safe for people and animals. A 22 lb. dog should be safe drinking up to 10 fluid ounces per day.

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    Re: How and why do borates suppress algae?

    A 22 lb. dog should be safe drinking up to 10 fluid ounces per day.
    I have given my dog a graduated cylinder with which to measure his intake but all that idiot wants to do is fetch it.
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    Re: How and why do borates suppress algae?

    I have given my dog a graduated cylinder with which to measure his intake but all that idiot wants to do is fetch it.
    My dog keeps attempting to do his laundry with it. Dummy doesn't even understand the warm/cold settings on the machine yet.
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    Re: How and why do borates suppress algae?

    Quote Originally Posted by PoolOwnerNumber9
    Algal toxicity: Green algae, Scenedesmus subspicatus 96-hr EC10 = 24 mg B/L* = 24 ppm.

    Can you please explain what these notations mean: 96-hr EC10?
    — AnnaK —

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    Re: How and why do borates suppress algae?

    Quote Originally Posted by AnnaK
    Quote Originally Posted by PoolOwnerNumber9
    Algal toxicity: Green algae, Scenedesmus subspicatus 96-hr EC10 = 24 mg B/L* = 24 ppm.

    Can you please explain what these notations mean: 96-hr EC10?
    Yes, Please!

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    Re: How and why do borates suppress algae?

    PO#9, please read the following:
    rules-on-copying-and-posting-material-from-other-sources-t4594.html

    Thanks,
    Sean
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    Re: How and why do borates suppress algae?

    PoolNumber9,

    Rather than cutting and pasting, it would be more helpful if you would just provide the links such as this one and this one which have some of the info you provided. That way, one can read more detail and get context while you can extract just part of the data. As Sean posted, there are rules about copying and pasting -- in particular, one needs to attribute the source so providing a link is a great way of doing that while not cluttering up this forum.

    The original Boron link I posted earlier (here) gives a list of abbreviations used for toxicity including the following common ones:

    LOAEL Lowest-observed-adverse-effect level (human and animal toxicity)
    LOEC Lowest-observed-effect concentration (environmental effects)
    MATC Maximum acceptable toxicant concentration (environmental effects)
    NOAEL No-observed-adverse-effect level (human and animal toxicity)
    NOEC No-observed-effect concentration (environmental effects)
    RR Rate ratio (or Relative risk)
    TLV Threshold limit value

    Other abbreviations may be found here including the following common ones:

    LC50 lethal concentration 50 percent kill
    LCLo lowest published lethal concentration
    LD50 lethal dose 50 percent kill
    LDlo lowest published lethal dose
    TC toxic concentration (other than lowest concentration)
    TCLo lowest published toxic concentration
    TD toxic dose (other than lowest toxic dose)
    TDLo lowest published toxic dose

    The EC10 definition may be found by looking for EC50 and finding this link or considering LOEC from above from which one can derive:

    EC effect concentration

    So, EC10 is the concentration that has an effect on 10% of the population being studied. So the "96-hr EC10 = 24 mg B/L = 24 ppm" means that when the green algae was exposed over a 96 hour period to 24 milligrams of Boron per liter which is the same as 24 ppm that 10% of the algae were affected which in this context (i.e. "toxicity") means killed.

    The safe upper limit of 1.6 mg/kg you quote (which is probably "per day") is probably too conservative (you also say 0.16 mg/kg, but I believe that is a typo). In any event, my main point of having dogs avoid daily drinking of pool water containing borates still stands.

    By the way, I cannot find any studies that show algae degradation of CYA. The loose reference of slow plant uptake of CYA as a source of nitrogen (fertilizer) is not something that would imply that this happens with algae to any great extent even though algae is a form of plant (it's single cell and far simpler, so isn't quite the same). Everything we've seen in pools losing CYA when "let go" is consistent with bacterial growth and not algae since some of the pools have been clear and not showed signs of algae (and others, as noted in this thread, are cloudy though not green, which is not as definitive).

    Any of us can use the Internet to search. What is more helpful is interpretation of such searched data by those with knowledge or skills. I usually stick with areas of inorganic chemistry (and general math such as applied to disinfection rates), for example, while others like mas985 (Mark) tend to stick with hydraulics such as pump curves (though he also performed the experiment that showed the non-linear protection effect of CYA shielding chlorine from breakdown from sunlight) and waterbear has unique expertise with water test systems, aquariums, general water chemistry (among other things). (There are many, many others, so don't feel slighted, y'all). Since you are a long-time service tech, your most valuable contribution would probably be the experience you have in what you have seen over the years and figured out from cause and effect. After all, theory isn't useful if it doesn't jibe with reality.

    Richard
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    Re: How and why do borates suppress algae?

    I just wanted to post a quick Thank-You to everyone who offered information, citations, and resources in this thread.

    From the paper Richard cited at InChem.org we were able to calculate the toxic borax dosage for our dogs who weigh between 65 and 85 pounds. Using the Pool Calculator, and knowing how much 20 Mule Team I've put in the pool, I was able to estimate the borax concentration in our 12,000 gallons. The bottom line is that they have to keep their daily pool water consumption to under 3 litres (very approximately 3 quarts). That's easy enough to control.

    This thread, though pretty technical, does include information which is necessary to all of us who have dogs that swim in our pools. So, thanks again.
    — AnnaK —

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    Re: How and why do borates suppress algae?

    I will review the posting rules and follow them. Please advise if postings need to be further adjusted.

    The 0.16mg/kg is accurate and works out to about 10.88 mg per day for a 150 lb. adult.
    Source: http://www.food.gov.uk/multimedia/pdfs/evm_boron.pdf

    The 1.6 mg/kg was my estimate of a conservative "safe" dose for a dog to drink every day (note: I did put “per day” in my post).
    ____________________________________________________________ _______________________________
    According to http://www.ehponline.org/docs/1994/Supp ... livan.html

    “The no-observed-adverse-effect-level (NOAEL) for boric acid was found to be equal to or greater than 125 mg/kg for rabbits and 450 mg/kg for mice. In the rat, a lowest-observed-adverse-effect-level (LOAEL) of 78 mg/kg resulted in decreased fetal weight. The developmental abnormalities noted, however, are found at or near the level that produce maternal toxicity.”
    ____________________________________________________________ _________________________________

    Another reference http://www.humco.com/assets/pdf/0030-Borax.pdf

    I think that there is a lot of room to debate what a "safe" dose would be for a dog to drink on a regular basis. I think that there is a lot of room between what is a "safe" dose and what is an "adverse" dose. I agree that it would be best to have the dog avoid drinking any pool water at all. However, it is always good to know, or at least have an educated opinion, about exactly what we are doing. There will always be dogs that drink the water. We should know how much is OK for them to drink on a regular basis. What is everyone's opinion about what is the highest safe dose for a dog to drink everyday? I think that 3 liters is a bit high, even for an 85 lb. dog. Possibly closer to 1 liter per day, every day; although 3 liters periodically would probably be fine.

    Note to Richard: Re your quote: "Since you are a long-time service tech, your most valuable contribution would probably be the experience you have in what you have seen over the years and figured out from cause and effect."

    Perhaps you did not mean it in any derogatory way, but to be clear, I do not need anyone trying to figure out some sort of niche that they can assign me to fit into. You do not know me. You do not know what I know and don't know. I will post whatever I feel can be helpful. If you disagree with something I say and want to challenge it, then do so. We don't always have to agree.

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    Re: How and why do borates suppress algae?

    From: http://www.food.gov.uk/multimedia/pdfs/evm_boron.pdf

    "The NOAELs for reproductive effects are 4.4 mg boron/kg bw/day in dogs and 9.6 mg boron/kg bw/day in rodents. Similar effects are observed in different animal species."

    This means that a 10 kg (22 lb) dog could ingest up to 44 mg per day, or about .88 Liters (29.8 fluid ounces) of water with a 50 ppm borate concentration. However, to be conservative, I used a somewhat arbitrary 1.6 mg/ kg of body mass per day, everyday.

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    Re: How and why do borates suppress algae?

    Could you put this in simpler terms so the majority of non technical forum users could benefit from it?

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    Re: How and why do borates suppress algae?

    Quote Originally Posted by PoolOwnerNumber9
    From: http://www.food.gov.uk/multimedia/pdfs/evm_boron.pdf

    "The NOAELs for reproductive effects are 4.4 mg boron/kg bw/day in dogs and 9.6 mg boron/kg bw/day in rodents. Similar effects are observed in different animal species."

    This means that a 10 kg (22 lb) dog could ingest up to 44 mg per day, or about .88 Liters (29.8 fluid ounces) of water with a 50 ppm borate concentration. However, to be conservative, I used a somewhat arbitrary 1.6 mg/ kg of body mass per day, everyday.
    Realize that the ppm borates that is normally expressed for pools is actually ppm boric acid and not boron. This will change your math. You might want to correct it.

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    Re: How and why do borates suppress algae?

    Quote Originally Posted by waterbear
    Could you put this in simperler terms so the majority of non technical forum users could benefit from it?
    I think that's why this thread is in the deep end.
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    Re: How and why do borates suppress algae?

    And adjust for estimated average daily dietary intake of boron, which was given as 1.2 mg per day in the InChem.org document. That source also cites a conversion factor of 0.113 for borax to boron (see section 2.3.2).
    — AnnaK —

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    Re: How and why do borates suppress algae?

    Quote Originally Posted by waterbear
    Realize that the ppm borates that is normally expressed for pools is actually ppm boric acid and not boron. This will change your math. You might want to correct it.
    Actually, the ppm Borates for pools is measured as ppm Boron, not boric acid. It's true that the primary chemical species in pool water is boric acid with a small amount of borate ion, but the measurement is in ppm Boron. This is why Michael Beach's calculator was incorrect because he used the molecular weight of boric acid instead of boron. It's also why something seemingly as low as 50 ppm has a rather large effect on pool water buffering. 50 ppm Boron is equivalent to 286 ppm boric acid. You and I figured this out a long time ago and there are posts somewhere about it.
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