I am moving to a house with fluoridated city-water.  I think reverse
osmosis is my best option for removing it.  I need to verify whether
human skin does absorb fluoride from the water in baths and showers. 
I saw one source that claimed that fluoride used to be added to baths
in the 1920's? to cool down overactive thyroid conditions.  If it is
absorbed, then a simple, low-volume, under-counter reverse osmosis
system, for cooking and drinking water system will only handle part of
the problem.  Whole house RO systems are very spendy.  Do I have other
options?  (I know that the term "fluoride" is not scientifically
precise, but it is enough to identify the stuff municipal water
providers add to domestic water supplies.)

Hello

Thanks for the interesting question.

There is plenty of thought-provoking information on the net about
whether fluoride can be absorbed through the skin.  A lot of it is
linked to an investigative journalist called George Glasser, an
American who publishes in Europe as well as at home.

His main points are these:

Above all there is a lack of evidence due to a lack of research done
in this area.  But his opinion is clearly that fluoride is scary
stuff, especially in the form in which it is commonly added to city
water supplies.

The EPA has described how many chemicals are taken in through the skin
(dermal absorption) but it has never done any studies of this in
relation to fluoride.  Nor has the US Public Health Service.

Nevertheless, the EPA's own reports state that children may be
particularly at risk of absorbing chemicals from bath water because of
a greater surface area to body weight area than adults, the greater
vulnerability of their developing physiology and because of their
enjoyment of long bath/play sessions.

There are other research projects which have highlighted how easy it
is to absorb toxins through the skin (though not specifically
fluoride.) Glasser cites a study done in the 1980s which suggests 64%
of waterborne contaminants are taken in through the skin.  He also
describes research at the University of Pittsburgh showing more
chemical exposure from showering in, than from drinking contaminated
water. (Though again there is no specific reference to fluoride.)

You can pursue thezse points at:
http://www.npwa.freeserve.co.uk/vulnerable.htm

There is an article Glasser published in The Ecologist at:
http://www.theecologist.org/archive_article.html?article=170&category=92

Other sites suggesting you should be concerned are at:  
http://www.wholly-water.com/d.cgi/BO90/Fluoride.htm
http://www.thirdworldtraveler.com/Environment/Bathtub_Toxic_Dump.html
http://www.greenparty.org.uk/reports/2000/fluoride/yorkassessment.htm

But you should be aware there is no widespread support for the idea
that dermal absorption of fluoride is a serious risk.
Find huge amounts of general information on fluoride and its problems
at:
http://www.fluoridealert.org/fluoridation.htm

So, if you want to avoid bathing in water with fluoride in, what can
you do?
Your question suggests you have already looked into this and
discovered reverse osmosis - a process that can remove 85-90% of
fluoride.

There doesn't seem to be anything betwen a large under-sink RO
apparatus capable of purifying up to 75 gallons a day or the
horrifyingly expensive whole-house systems. ($8000 or so.)  Examples
of these are at:
http://www.raindancewatersystems.com/whole-house-reverse-osmosis.html
http://www.raindancewatersystems.com/reverseosmosis.html
If you do decide to purchase, there is plenty of consumer buying
advice at:
http://directory.google.com/Top/Home/Consumer_Information/Appliances/Water_Filters/

You ask "do I have any other options?" and I fear the answer may be
no.  I hope you won't find this idea too ecentric - but if you have
small children, I wonder if you would consider going back in time to a
system of heating water from the sink faucet for their baths?  Then
you would only need the $500 or less under-sink option if the adults
were prepared to risk absorbing some fluoride.

Good luck with making a decision on this complex subject.  Let me know
if I can clarify anything.

P.S.

You mention a connection between fluoride and thyroid problems.  More
about this at:
http://www.thyroidtears.co.uk/fluorideantagonist.html    




search strategy terms:
fluoride skin dermis absorb "dermal absorption" bath shower
"reverse osmosis" treatment domestic residential "whole house" "water
purification"

Great answer!  I had not yet encountered Glasser's work.  I wish there
was another, non-RO answer for us, but we have vulnerable young
children and we have to do something.  One has already had significant
damage to his teeth due in part to prescribed fluoride drops (when we
had well water).  Maybe we'll try catching (and filtering) rain water
instead!

Good answer, 
       but not complete. You do have other options then RO,
       not nececearly more economical: 

 Each type of filtration system reduces fluoride content: 
the activated carbon filter (81% reduction), the
reverse osmosis system (84% reduction), 
and the distillation unit (99% reduction)
 http://216.239.35.100/search?q=cache:yqhXouKR3KMC:www.dhfs.state.wi.us/heal
th/Oral_Health/pdf_files/pph4559.pdf+reverse+osmosis+fluoride&hl=en&ie=UTF-8

There are other methods (listed for As, but applicable to F as well):
http://www.epa.gov/safewater/ars/treat.html  

 Alumina filters may be least expensive solution:
http://www.pwgazette.com/fluorideinwater.htm
There are cartriges for $37 offered here:
http://www.pwgazette.com/cdsdiaal.htm
or here:
http://www.purewater4u.com/store/specialtyAAL.shtml

Even less expensive, but perhaps less verified and less suitable for
residential treatment is use of bauxite:
http://www.indian-express.com/ie/daily/19981029/30250034.html
     
There are less expensive  Point of Entry (POE) Whole-house Filters
then $8000
  http://www.purewaterexpress.com/

 If you really want to spend lot of money, it is important to verify
 the vendor claims. There are kits and services which will test your
water  ...

 That may be another question and I would defintly probe more the the
 risks at given concentration. EPA established the standard somehow -
 there must be some study behind that. Discussion of the effect of
different concentrations is here:
http://www.centralsupplyinc.com/statenh/ws-3-5.htm


 For now, just a comment : it looks likely that shower
will reduce absorbtion compared to bath and:

 If you own a house - did you consider digging a well in the city?

The Food and Nutrition Bureau of the National Academy of Sciences
recognizes fluoride as an Essential Nutrient with a Recommended Daily
Allowance of 1 mg for prevention of osteoporosis and dental carries.