Week 6: Halogen of the Week

What is the difference between Chlorine and Bromine?

I love the water and its therapeutic benefits, and yet I really despise the feeling and smell of chlorine.  It makes my skin feel dry and unhealthy.  When I’ve had a hot tub in the past, I’ve used Bromine as alternative but didn’t really know how it’s different than Chlorine…so I’m inspired to do a bit of research.  I am now convinced that halogens are not well suited for water purification in terms of therapeutic benefits.  While they may be effective at sanitation, they are toxic and carcinogenic.   I think the only way this will shift out of popularity is by consumer demand.  While it is more expensive to use salt and ozone purification systems, if people demand them in public pools and spas, the “norm” will definitely shift to less toxic options.

Bromine (Br): 

  • Atomic Number 35
  • Means “stench (of he-goats)”
  • Is a reddish-brown volatile liquid at standard room temperature that is intermediate in reactivity between chlorine and iodine.
  • Bromine vapors are corrosive and toxic
  • Bromine is most commonly used as a fire retardant, but is also used in other applications such as water purification.

Chlorine (Cl):

  • Atomic Number 17
  • In its elemental form, it’s a pale green gas about 2.5 times as dense as air
  • Its poisonous and is a powerful oxidant used in bleaching and disinfectants.
  • In the upper atmosphere, chlorine-containing molecules have been implicated in the destruction of the ozone layer.


So both are halogens, although the use of bromine in pools and spas is much more recent than chlorine.  Bromine came into use in pools/spas in the early 1980’s, and at first it appeared to be the best thing for spas and hot tubs. It is more stable in water than chlorine since it has a very high evaporation point as compared to chlorine. Less of it escapes from the tub as a gas.  I found an article that talks about “Chlorine vs. Bromine” http://www.thesolar.biz/hot_tub_faq.htm

Bromine continues to sanitize the water even after it combines with organic compounds to form bromamines. When chlorine combines to form chloramines, they are at best a nuisance and just serve to sting your eyes and smell up your tub.

So, bromine seemed like a great thing when it first appeared. But then the industry started to pick up on the problems with bromine. It was so stable that it was difficult to get into the water. Erosion feeders needed to be supplied with a mixture of one third chlorine and two thirds bromine so the chlorine could give the bromine a “kick”.

They’re have also been reports that bromine is not as wide spectrum a sanitizer as chlorine. That is, there are some forms of organisms, most notably certain forms of either a black fungi or algae according to anecdotal reports, that are not susceptible to bromine.

Furthermore, because bromine is so stable, its odor is much more difficult to wash off the skin after bathing. And, those wonderful bromamines that maintained their ability to sanitize? It turns out that they are far more carcinogenic (cancer causing) than their chloramine cousins.

With chlorine there are three basic types, liquid, sodium-trichlor and sodium dichlor. The first two should only be used in swimming pools. Liquid chlorine will throw your pH so far out of wack it will be nearly impossible to balance your water. With the trichlor, the higher temperatures of hot tubs tends to make it a little caustic to your skin. If you choose to use chlorine, sodium-dichlor is the way to go.

The fact that both bromamines and chloramines are carcinogenic is reason enough to consider eliminating halogens with an ozonator. After years of experience, we have come to the opinion that if you must use halogens, granulated chlorine added manually is still the best method. This way, you have complete control over the process.

Regardless of which halogen you use and regardless of the method you employ to get it into the water, testing will be required to verify that the halogen levels are neither too high nor inadequate.

The thing that strikes me is that these are so commonly being used in pools and spas, which are largely “therapeutic” in nature.  It is disturbing that these halogens are the most popular forms of sanitation and purification because they distort the larger context of “purification” given that they’re so toxic.


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