Chlorine & Clorox Bleach Health Concerns

[kbaumann]

I need to know anything you know to be negative to peoples health useing chlorine. ~ Karl

[chem geek]

Why?

[kbaumann]

Why I need this information is because the system I am putting in place will have me using Clorox 6% Bleach with a Nature 2 spa system and MPS... Because of this I must know every health risk there is so I can weigh out weather it is beneficial to use... I would like even information that was "heard through the grapevine" so I can study to see if it carries any weight... So information without facts will even help... Don’t worry about giving me that kind of information, I will study and base my decisions on facts and studies alone. Thank you s much for the time invested in helping me! Best Regards, Karl

[chem geek]

There is a lot of information on the disinfection by-products (DBPs) produced from chlorine combining with ammonia and organics. The main concerns with chlorine aren't with chlorine itself so much as with the DBPs. Of those normally found in pool or spa water, the most smelly and irritating is nitrogen trichloride. Dichloramine and monochloramine can also be smelly if in higher concentrations. The monochloramine is often associated with bad pool smell in pools that are improperly sanitized with too little chlorine since sufficient chlorine will generally oxidize monochloramine before it gets to levels you can detect. Overuse of CYA will lead to this as well since it slows down all chlorine reactions (too much, if the CYA level is too high; technically if the FC/CYA ratio is too low). Nitrogen trichloride may be able to be minimized by using lower active chlorine concentrations (FC/CYA ratios) so one tries to find a sweet spot where the FC/CYA ratio is high enough to not build up monochloramine and to oxidize bather wastes quickly enough and to kill pathogens quickly enough, but not so high as to increase nitrogen trichloride production. Note that many indoor pools do not use CYA and their active chlorine levels may lead to significantly higher nitrogen trichloride production.

The other main DBP is chloroform which is chlorine combining with methyl groups (as in a methyl ketone) that can come from the oxidation of organic compounds (such as citric acid or humic acid). Interestingly, the reaction is catalyzed by copper ions so using copper-based algicides or as supplemental sanitation along with chlorine would make the production of chloroform more rapid (see here). There are many other DBPs, but these two are the most common and often in the largest quantities (for ones of concern). Reducing the amount of soil that gets into the water helps a lot to keep the chloroform levels lower as well as limiting the bromine-related compounds. The DBPs usually found in pool/spa water include the following (where I show odor thresholds, they are the lowest from various sources which unfortunately are inconsistent):

Inorganic Chloramines:

Monochloramine (NH₂Cl) -- odor threshold 0.65 ppm

Dichloramine (NHCl₂) -- odor threshold 0.1-0.5 ppm (100-500 ppb)

Nitrogen Trichloride (NCl₃) -- most smelly and irritating; odor threshold 0.02 ppm (20 ppb); very volatile; may be related to asthma

Trihalomethanes (THMs):

Chloroform (CHCl₃) -- EPA lists this as a carcinogen "likely under high exposure conditions" (here; high odor threshold (> 85 ppm in air)

Bromoform (CHBr₃) -- EPA lists this as a "probable" carcinogen (here)

Dibromochloromethane (CHBr₂Cl) -- EPA lists this as a "possible" carcinogen (here)

Dichlorobromomethane (CHBrCl₂) -- EPA lists this as a "probable" carcinogen (here)

Other Volatile Disinfection By-Products:

Cyanogen Chloride (CNCl) -- no EPA carcinogen data; strong eye and skin irritant and highly volatile (toxic at higher concentrations); minimized by maintaining chlorine

Cyanogen Bromide (CNBr) -- no EPA carcinogen data

Dichloroacetonitrile (CNCHCl₂)

Dichloromethylamine (CH₃NCl₂)

Note that the amount of such chemicals is not only related, in some cases, to the active chlorine concentration, but to the bather load and as I noted above to the nature of that load (e.g. is soil brought into the water). Also note that concentration means everything since there are many substances that are carcinogenic that you are exposed to in daily life so while such exposure should be minimized, if the levels are already very low then the risk is far lower than with many other substances. Fortunately, many of the substances have low odor thresholds so you can tell, to some extent, the quality of your pool/spa water from the smell (which should only have the faint "clean" bleach-like smell, if anything). Unfortunately, this is not the case with chloroform which has a high odor threshold.

I'm sure you will be able to find a lot of info on the Internet since anyone selling a low or no chlorine product will reference any study they can find with regard to the problems of DPBs. If you are going to use N2 with MPS as the primary oxidizer/sanitizer, then this should oxidize many of the organic compounds (and ammonia) thus preventing formation of many of the DPBs. Such oxidation may produce different compounds, but they are less likely to be of concern though no definitive studies have been made for such substances specifically.

For more info on volatile DPBs in swimming pools (and spas), you can purchase some of the cutting-edge research that Dr. Ernest "Chip" Blatchley and his team have been doing here and here. Some of this research is funded by the National Swimming Pool Foundation (NSPF) and given the frank and honest science being done, hats off to NSPF for helping to get this work done. Another set of research (most certainly not funded from NSPF) is from Dr. Albert Bernard, though it isn't as core (especially his second paper) since its more epidemiological and retroactively statistical in nature -- I write about some of his research in this thread.

The second Dr. Blatchley paper I reference above looked at 10 indoor swimming pools and 1 indoor spa. Because these appeared to be higher bather load commercial or public pools and because they were indoors, I would assume that most if not all of them did not use CYA in the water. Nevertheless, I think it's useful to see the min/avg/max values of the various chemicals I listed above for these pools and spa. Just keep in mind that a residential pool has far lower bather load, often by a factor of 10. A residential spa usually has a fairly high bather load because the water volume is small. On the other hand as was seen in the results described in the paper, the spa had far lower THMs and this may be a result of the hotter spa temperatures driving off the volatile DPBs and the fact that the water is changed periodically. So I repeat the table from above, but give measurements which are ranges of the average mesurement for the 10 pools and the average measurement for the 1 spa (separately). These averages are of from 25-40 water samples for each pool/spa. All measurements are in µg/L which I denote below as ppb (parts-per-billion).

Inorganic Chloramines:

Monochloramine (NH₂Cl) -- 130-492 ppb (as Cl2) for pools; 186 ppb (as Cl2) for spa

Dichloramine (NHCl₂) -- 42.9-188 ppb (as Cl2) for pools; 98.5 ppb (as Cl2) for spa

Nitrogen Trichloride (NCl₃) -- 10.01-154 ppb (as Cl2) for pools; 141 ppb (as Cl2) for spa

Trihalomethanes (THMs):

Chloroform (CHCl₃) -- 24.4-138 ppb for pools; 16.2 ppb for spa

Bromoform (CHBr₃) -- .999-54.8 ppb for pools (only one pool 54.8; max of 4.4 for all others); 1.12 ppb for spa

Chlorodibromomethane (CHBr₂Cl) -- 1.2-35.3 ppb for pools; 0.605 ppb for spa

Dichlorobromomethane (CHBrCl₂) -- most readings below detection limit for pools and spa; max of any sample was 150 ppb

Other Volatile Disinfection By-Products:

Cyanogen Chloride (CNCl) -- 2.81-17.3 ppb for pools; 2.27 ppb for spa

Cyanogen Bromide (CNBr) --3.03-31.1 ppb for pools; 5.13 ppb for spa

Dichloroacetonitrile (CNCHCl₂) -- 7.03-31.4 ppb for pools; 16.3 ppb for spa

Dichloromethylamine (CH₃NCl₂) -- 4.11-18.7 ppb (as Cl2) for pools; 8.98 ppb (as Cl2) for spa

One thing to note is that the (presumed) lack of CYA tends to keep the monochloramine and dichloramine levels lower but has the nitrogen trichloride level higher. The odor threshold for monochloramine of at least 650 ppb (some say it's 5 ppm which is 5000 ppb) and for dichloramine of 100-500 ppb (some say it's 800 ppb) means that these are probably not noticed, but the 20 ppb odor threshold for nitrogen trichloride is exceeded in many of the pools and in the spa so is probably noticeable and potentially even irritating. If one used CYA and higher FC levels for an effective chlorine level that is lower by about a factor of 4 in the spa and a factor of 7 for the pools, then one would theoretically cut down the nitrogen trichloride levels by roughly those factors, but would increase monochloramine and dichloramine by those factors as well, on average. Clearly, supplemental oxidation is needed in these pools and spa. With chlorine alone, all one can do is tune between these chloramine amounts but they will still be too high no matter what you do using chlorine alone. Non-chlorine shock (MPS), ozone and/or UV would be helpful in these higher bather load situations in commercial/public pools where one still wants sanitizer levels to be high enough during the soak to prevent person-to-person transmission.

The Bernard and other asthma studies seemed to indicate that levels of nitrogen trichloride could trigger asthma somewhere starting in the 61-102 ppb range, but as I point out above, there may be a relatively easy solution for that by using lower effective chlorine levels by using CYA. The German DIN 19643 standard sets the chlorine level to 0.3-0.6 ppm with no CYA partly for this reason (0.2-0.5 ppm if ozone is also used), but it's harder to consistently achieve that low chlorine level when there is localized bather load (including urinating children) and that system also dechlorinates the water on every filter pass since they use activated carbon filters to remove all chloramines so that supplemental oxidation as well as coagulation/flocculation can remove more monochloramine and organic precursors.

As for the THMs, the EPA limit for drinking water is 80 ppb which is based on increased cancer risk of between 1 in 100,000 and 1 in 1,000,000 for a lifetime of drinking 2 liters per day. There is a dearth of specific studies (which would generally be epidemiological) on humans; most studies are on rats or mice. For chloroform, this link indicates a 1 in 1,000,000 increased cancer risk at the level of 0.26 mg/day which would be 130 ppb drinking 2 liters of water. This link indicates that dermal absorption is at a lower rate and is temperature dependent. For bromoform, the 1 in 1,000,000 increased cancer risk from the EPA is at 4 ppb (1 in 100,000 risk at 40 ppb). Dibromochloromethane has 10 times the projected risk of bromoform so 0.4 ppb at 1 in 1,000,000 and 4 ppb at 1 in 100,000. Dichlorobromomethane is roughly similar at 0.6 ppb for 1 in 1,000,000 and 6 ppb for 1 in 100,000 increased risk.

So while I would say that indoor heavy bather load commercial/public pools aren't in as good shape as they probably should be to have reasonably low risks, that's probably not the case at all for residential pools with their significantly lower bather loads (i.e. they are probably vastly safer). As for spas, there aren't enough data points though it does look encouraging that the higher temperatures and more regular water replacement may be keeping a check on the THMs. The practice (on this forum) of having a low chlorine level (1-2 ppm FC) at the start of a soak possibly minimizes exposure since most of this chlorine will form monochloramine (and possibly chlorourea) during the soak from the ammonia (and urea) in sweat and urine. The addition of additional chlorine after the soak takes care of the rest of the bather waste and also has an excess that would continue to react with organics to produce small amounts of THMs, but these would be outgassed. Keeping the cover off for a time when the chlorine is added after a soak and even more importantly taking the cover off and letting the spa air out before the soak should minimize exposure. Of course, this is just reasonable speculation at this point since no specific research on this has been done.

I find it encouraging that those spa users who target 1-2 ppm FC before their soak, and then add sufficient chlorine afterwards (in particular, Dichlor-then-bleach users) to handle their bather load, notice virtually no smell except perhaps the faint "clean" chlorine smell at the very start of the soak. Note that though copper ions increase the rate of production of chloroform, Nature2 for spas contains silver and zinc and not copper. Nature2 for pools, however, contains copper as do some copper-based algicides.

[OttawaGreg]

Why I need this information is because the system I am putting in place will have me using Clorox 6% Bleach with a Nature 2 spa system and MPS... Because of this I must know every health risk there is so I can weigh out weather it is beneficial to use... I would like even information that was "heard through the grapevine" so I can study to see if it carries any weight... So information without facts will even help... Don’t worry about giving me that kind of information, I will study and base my decisions on facts and studies alone. Thank you s much for the time invested in helping me! Best Regards, Karl

Karl,

Just an FYI. I am using Clorox 6% bleach, MPS, and have the Nature2 in my filter. After a recent cloudy water incident, because I was out of town for longer then expected and hadn't topped up the bleach or put in my floater, I am in the opinion that Nature2 does little to nothing. I paid $40 for this thing and when it could/should have kicked in it went absent. Come March I will be removing it and continuing along as I have been and will see if there is any difference. At $40 a four month cartridge that's $10 a month.. for what? ... If all I need to do is add more MPS then fine, I'll add it more often and forgo Nature2.

Just my 2 cents.

Greg

[Mikey_in_NY]

Why I need this information is because the system I am putting in place will have me using Clorox 6% Bleach with a Nature 2 spa system and MPS... Because of this I must know every health risk there is so I can weigh out weather it is beneficial to use... I would like even information that was "heard through the grapevine" so I can study to see if it carries any weight... So information without facts will even help... Don’t worry about giving me that kind of information, I will study and base my decisions on facts and studies alone. Thank you s much for the time invested in helping me! Best Regards, Karl

For what it's worth I've been using this method very successfully now for nearly 5 months with no problems (changed water first time about a month ago). The water is always well balanced in terms of PH, FC, CC and TA. My tub also has an ozonator.

Just like OttawaGreg I'm also unsure if I need to be spending $40 every 4 months on a Nature2 cartridge, but because I've had no problems with my water chemistry I'm just gonna keep on with the same old regime (if it ain't broke don't fix it).

Like Chem geek said I usually get a mild 'bleachy' / ozone smell when I lift the cover, but apart from that there's very little odor. Probably too late to worry about it now anyways as I've been drinking and bathing in chlorinated water from the faucet for the last 50 years.

[kbaumann]

I need to have an insurance system in place... So I must have a Nature 2 kind of system... Im concern about the clouding though...

[chem geek]

Greg,

The silver ions in Nature2 should have prevented uncontrolled bacterial growth so I'm not sure where the cloudiness came from unless the levels were too low (i.e. Nature2 wasn't working as it should) or it was something else (some mold or algae, though the latter is rare in spas). Also note that the silver ion rapidly decomposes the most irritating component of MPS which is potassium persulfate (aka potassium peroxydisulfate) so if you stop using the N2 see if you find irritation from the MPS, especially if you add any before the soak. Also, the silver ion combined with MPS provides for greater sanitation, though that's mostly to pass EPA DIS/TSS-12 which is an extraordinarily strong standard that doesn't represent reality when stabilized chlorine (Dichlor or Trichlor) is used and builds up even a little. For the record, MPS alone is not an EPA-registered sanitizer.

Richard

[OttawaGreg]

Greg,

The silver ions in Nature2 should have prevented uncontrolled bacterial growth so I'm not sure where the cloudiness came from unless the levels were too low (i.e. Nature2 wasn't working as it should) or it was something else (some mold or algae, though the latter is rare in spas). Also note that the silver ion rapidly decomposes the most irritating component of MPS which is potassium persulfate (aka potassium peroxydisulfate) so if you stop using the N2 see if you find irritation from the MPS, especially if you add any before the soak. Also, the silver ion combined with MPS provides for greater sanitation, though that's mostly to pass EPA DIS/TSS-12 which is an extraordinarily strong standard that doesn't represent reality when stabilized chlorine (Dichlor or Trichlor) is used and builds up even a little. For the record, MPS alone is not an EPA-registered sanitizer.

Richard

Hey Richard,

The recipe for Nature 2 has you adding more MPS and Dichlor then I want to being on the bleach method. If I'm going to be adding that much MPS & Dichlor then why do I need the Nature 2? That is the question that bothers me.

I was convinced by the sales guy to give it a try and I am. Only once I take it out of my tub in March will I see it's true effect. I currently use a good deal of bleach after each use and say 1-2 tbsp of MPS a week. If I am going to be away for more then 1-2 nights then I drop in a floater with a tab of compressed chlorine. This is what I didn't do after it's last use and didn't visit it for 4 days. The water was a shade of brown, scary. It was just the water though and I shocked it and it's back to pristine self. I just wonder where the Nature 2 was during this "holiday" ;-).

Greg

[Eric W.]

The recipe for Nature 2 has you adding more MPS and Dichlor then I want to being on the bleach method. If I'm going to be adding that much MPS & Dichlor then why do I need the Nature 2? That is the question that bothers me.

I was convinced by the sales guy to give it a try and I am. Only once I take it out of my tub in March will I see it's true effect. I currently use a good deal of bleach after each use and say 1-2 tbsp of MPS a week. If I am going to be away for more then 1-2 nights then I drop in a floater with a tab of compressed chlorine. This is what I didn't do after it's last use and didn't visit it for 4 days. The water was a shade of brown, scary. It was just the water though and I shocked it and it's back to pristine self. I just wonder where the Nature 2 was during this "holiday" ;-).

I was using the Sundance nature 2 cartridge and MPS/Chlorine since my tub was new in June, and I found if I went more than 2 days after adding chlorine I was greeted by a cloudy tub. The last straw was over the holidays when it was 10 degrees and snowy, so I didn't think about going out there to add chlorine, and I came out to a cloudy tub. I don't know what the Nature 2 cartridge was doing for me, but it seems after 2 months I get no benefit from it, and must add chlorine daily to keep it it clear.

The Monday following Christmas, I made the switch to Bromine. My tub has a bromine dispenser in the weir gate, so I followed instructions found elsewhere here and I'm happier. I checked the levels daily for over a week and I'm now confident to add bromine tabs to the dispenser and shock it once a week.