Borate Toxicity?

[ThinkPad]

I was reading through a couple other threads on borates when I discovered the toxicity issue. What risk would a pool with borates of 50 ppm do to cats? I have a couple of cats that drink out of the pool. I know for dogs they have to drink 8 liters per day before even being still being considered at risk.

I am also interested in the risk for humans.

Would other pool chemicals be higher risk than borates?

 

[zea3]

I don't know the specific risk to cats from borates, but encourage them not to drink from the pool (squirt gun) and provide plenty of fresh water nearby.

 

[ThinkPad]

We do provide water in bowls for them, but my sisters tell me they just see the cats drinking from the pool. From the cat's mind: why go looking around for bowls they probably don't even know have water in them, when there is a large pool in the ground.

We wouldn't be able to always catch them when they are drinking from the pool.

I haven't borated yet, just deciding if I should consider it or not.

How about other chemicals in the pool, and the risk of borates to humans (if there are any)?

 

[chem geek]

For details, see the thread Are Borates Safe to Use? The only testing with cats was the same done for dogs and rabbits for the acute oral LD₅₀ which is the lethal dose where 50% of the animals die. This was in the range of 250-350 mg/kg of body weight. A typical cat is usually more than 8 pounds so 3.6 kg so would have to drink (3.6*250)/50 = 18 liters for a lethal dose. Since the lethal dose for cats was similar to that of dogs, we can use the No Observed Adverse Effect Limit (NOAEL) for dogs which is 8.8 mg/kg/day which for a 3.6 kg cat is (3.6*8.8)/50 = 0.64 liters or 2.7 cups. Cats do not drink very much water as they are supposed to get more of their water requirements from wet food and there is no way they drink close to cups of pool water every day.

So your cats are probably fine. It's dogs that are more of a concern since they tend to drink a lot more (even accounting for their body weight) though even then they are not likely to drink so much as to be affected. Nevertheless, it gets close enough given intra-species variation (variation between members of the same species) that if one has a dog it's probably best to train them not to drink from the pool or to consider not using borates.

As for people, the EPA uses a Margin of Exposure (MOE) safety factor of 100 -- a factor of 10 for intra-species variation and a factor of 10 for inter-species variation. This is very conservative. With the 8.8 mg/kg/day, they assume oral exposure of 8.8/100/50 = 1.76 ml/kg of body weight. So for a 50 kg (110 pound) person this is 88 ml or 3 fluid ounces. Remember that this would have to be every day for months and even then this is with a factor of 100 safety margin and still at the No Observed Adverse Effect Limit. Without the safety margin, it's 9.3 quarts per day. So unless people drink a lot of pool water every day, it's very unlikely they are at risk. That's why the EPA set the limits where they did at 50 ppm Boron for swimming pools -- they tend to be fairly conservative and safe.

As for other chemicals in the pool, they are even safer at their levels in the pool. Nevertheless, if your pool is a salt pool with 3000 ppm salt, you wouldn't want to drink large quantities. It wouldn't kill you, but it would equal the recommended 1500 mg salt per day by drinking just half a liter (about 2 cups). Basically, pool water is not for drinking. It's for swimming.

 

[ThinkPad]

Thank you chem geek! That was very informative. I plan on borating this year. Fortunately, my dogs are indoor dogs.

 

[DogsHouse_MyPool]

My dog stopped drinking the water when I went SWG earlier this year, so I'm not too worried about borax at this point.

 

[ThinkPad]

I know this a tad bit off topic, but how much chlorine would I save by having borates? Does anyone know a percentage?

 

[bobodaclown]

You use the same amount of chlorine. It buffers PH rise, and are able to run lower TA. Makes the water feel smoother, and some say more sparkly.

 

[ThinkPad]

Oh, I thought that borates reduced chlorine usage. Maybe because if buffers the pH and makes the chlorine more effective for extreme cases of pH bounce.

 

[chem geek]

Not really. The only practical way that borates could reduce chlorine usage is via its mild algaecidal properties. So if you were on the edge of algae growth because you weren't consistently maintaining a sufficient FC/CYA ratio, then the borates could help suppress the algae thereby reducing the amount of chlorine that got consumed trying to kill/oxidize the algae.

For a saltwater chlorine generator (SWG) pool, one can get scaling in the salt cell at the hydrogen gas generation plate and the use of borates will reduce that significantly via it's pH buffering effect so if such scaling was enough to reduce the chlorine output from the SWG, then it would appear as if borates helped to reduce chlorine demand though technically it improved the rate of chlorine production.