Question For The Chemistry Experts

[raydz]

Recently I found out that I am allergic to products that contain MPS. I use Bromine in my hot tub as a sanitizer. My understanding is that you can use either chorine or MPS to "activate" the Bromine. Chlorine gets totaly converted to Bromine. Does anyone know if MPS is converted in a way that the MPS allergy would not happen? I'd like to have the option of using either if possible.

[chem geek]

MPS is composed of a salt of three components. One is essentially potassium sulfate (K2SO4), another is potassium bisulfate (KHSO4) which is very similar to sodium bisulfate aka "dry acid", and the third which is the active component that is double in quantity is potassium peroxymonosulfate (KHSO5). If you have a general allergy to sulfates, then these will NOT go away when activating bromide to bromine (and you should not use "dry acid" in your spa in that case since you would be allergic to sulfates generally). If your allergy is specific to peroxymonosulfate, then most of this will get broken down converting bromide to bromine, but there will likely be a residual left. After about 8 hours, this residual may be low, but if you are allergic I don't think you'd want to take the chance, but I can't really say if you will be affected (you could see -- assuming your allergy isn't really bad -- i.e. if it's just a rash that goes away or something like that).

The downside to using chlorine instead of MPS is that if there are organics left in your pool that bromine has not oxidized, then using chlorine can form chlorinated organics which measure as Combined Chlorine (CC) and some of these can be smelly and some are even carcinogenic. Shocking with MPS does not produce such compounds. So there's a bit of a catch-22 by not using MPS, but assuming your bromine levels are always well-maintained, then the amount of organics in the pool will hopefully be low so that chlorine shocking won't from a lot of CCs. If you buy a good chlorine test kit that can measure CCs (the best are drop-based FAS-DPD test kits), then that could tell you more about your situation, but I can't really predict it in advance.

Personally, I think you'll be fine using chlorine for shock instead of MPS, but just wanted to give you the various possibilities.

[raydz]

MPS is composed of a salt of three components. One is essentially potassium sulfate (K2SO4), another is potassium bisulfate (KHSO4) which is very similar to sodium bisulfate aka "dry acid", and the third which is the active component that is double in quantity is potassium peroxymonosulfate (KHSO5). If you have a general allergy to sulfates, then these will NOT go away when activating bromide to bromine (and you should not use "dry acid" in your spa in that case since you would be allergic to sulfates generally). If your allergy is specific to peroxymonosulfate, then most of this will get broken down converting bromide to bromine, but there will likely be a residual left. After about 8 hours, this residual may be low, but if you are allergic I don't think you'd want to take the chance, but I can't really say if you will be affected (you could see -- assuming your allergy isn't really bad -- i.e. if it's just a rash that goes away or something like that).

The downside to using chlorine instead of MPS is that if there are organics left in your pool that bromine has not oxidized, then using chlorine can form chlorinated organics which measure as Combined Chlorine (CC) and some of these can be smelly and some are even carcinogenic. Shocking with MPS does not produce such compounds. So there's a bit of a catch-22 by not using MPS, but assuming your bromine levels are always well-maintained, then the amount of organics in the pool will hopefully be low so that chlorine shocking won't from a lot of CCs. If you buy a good chlorine test kit that can measure CCs (the best are drop-based FAS-DPD test kits), then that could tell you more about your situation, but I can't really predict it in advance.

Personally, I think you'll be fine using chlorine for shock instead of MPS, but just wanted to give you the various possibilities.

Thanks for the great answer! In my case... I had just re-filled the hot tub and put in some MPS as an initial shock. Went in about 5 hours later... and had a rash. Nothing terrible... just annoying. I'm hoping it disapates enough not to cause any problems.... I have'nt been in for 3 days and have just been maintaining the bromine at 3ppm. I run ozone and a mineral cartridge. I don't feel like dumping the water again so soon if I don't have to.

[chem geek]

Well, let us know how it is to get back in after a few days. If you don't get a rash, then perhaps the "waiting a day" after adding MPS might do the trick. In some sense, your allergy is an MPS measurement kit Well, maybe that's over the top -- I'm sure having that kind of allergy is unpleasant, but at least you know what triggers it rather than just randomly finding youself with a rash.

[waterbear]

The downside to using chlorine instead of MPS is that if there are organics left in your pool that bromine has not oxidized, then using chlorine can form chlorinated organics which measure as Combined Chlorine (CC) and some of these can be smelly and some are even carcinogenic. Shocking with MPS does not produce such compounds. So there's a bit of a catch-22 by not using MPS, but assuming your bromine levels are always well-maintained, then the amount of organics in the pool will hopefully be low so that chlorine shocking won't from a lot of CCs. If you buy a good chlorine test kit that can measure CCs (the best are drop-based FAS-DPD test kits), then that could tell you more about your situation, but I can't really predict it in advance.

Personally, I think you'll be fine using chlorine for shock instead of MPS, but just wanted to give you the various possibilities.

In a bromine system you do not worry about bromamines since they are considered to be effective sanitizers (unlike chloramines). Also, unless there is NOT a 30 ppm level of bromide in the water (which is easily achieved in a bromine system by ALWAYS adding the sodium bromide on each refill) then any chlorine added will convert to bromine sanitizer and if any bromamines form it's not a big deal. In fact, in a bromine system the Taylor FAS-DPD test for bromine (such as in the Taylor K-2105 kit) and all other test kits I have ever seen, including strips, only tests for TOTAL bromine for this reason. Bottom line, although chlorine and bromine are similar in some ways there are major differences in how the two systems are used and tested (and what is a major problem with one [chloramines] becomes moot in the other[bromamines]).

Also, bromine is a known sensitizer and does commonly cause a rash in some people. (What else is in the product that 'contains MPS' that you are allergic to? Are you sure you are not allergic to the bromine itself?) You can try using only chlorine for "shocking" on your next refill to see if it eliminates the problem. That way you know if your rash is caused by the MPS or the bromine! IF it's from the bromine then I would suggest switching to chlorine for sanitizing. I would use biguanide only as a last resort as my choice of sanitizer if there were also problems with chlorine.

[raydz]

In a bromine system you do not worry about bromamines since they are considered to be effective sanitizers (unlike chloramines). Also, unless there is NOT a 30 ppm level of bromide in the water (which is easily achieved in a bromine system by ALWAYS adding the sodium bromide on each refill) then any chlorine added will convert to bromine sanitizer and if any bromamines form it's not a big deal. In fact, in a bromine system the Taylor FAS-DPD test for bromine (such as in the Taylor K-2105 kit) and all other test kits I have ever seen, including strips, only tests for TOTAL bromine for this reason. Bottom line, although chlorine and bromine are similar in some ways there are major differences in how the two systems are used and tested (and what is a major problem with one [chloramines] becomes moot in the other[bromamines]).

Also, bromine is a known sensitizer and does commonly cause a rash in some people. (What else is in the product that 'contains MPS' that you are allergic to? Are you sure you are not allergic to the bromine itself?) You can try using only chlorine for "shocking" on your next refill to see if it eliminates the problem. That way you know if your rash is caused by the MPS or the bromine! IF it's from the bromine then I would suggest switching to chlorine for sanitizing. I would use biguanide only as a last resort as my choice of sanitizer if there were also problems with chlorine.

After waiting a week ...since adding the MPS and maintaining the Bromine at 3ppm (with ozonator) I went in........ and within hours... had a rash.

I took the easy way out this time... I already had Baqua spa chemicals.... so I drained, cleaned and started up with Baqua spa. I have never had any real problems with it. Allergy is gone !

I would like to find out which component (MPS, Bromine) is causing the problem.... I might have to go to an allergist to isolate the allergy.

I'll keep everyone posted...