theClinical Inquiries From
Family Physicians
Inquiries NetworkDavid Oldham, DO

341st Medical Group,
Malmstrom Air Force Base,MontanaPaul Crawford, MD

Nellis Air Force Base
Family Medicine Residency,
Nellis Air Force Base, Nevada

William Nichols, Librarian
Eglin Air Force Base, Florida

What is the best portable
method of purifying waterto prevent infectious disease?  

Evidence-based answer

There isn’t a single best method, but there
are 5 that adequately purify water according
to Environmental Protection Agency (EPA)
standards. These include 1) boiling for 1
minute if below 2000 m (6562 feet) and3 minutes if above, 2) chlorine dioxidetablets, 3) MIOX purifier, 4) ultraviolet
light (SteriPEN), and 5) portable filtration

with a absolute pore size <1 micrometer
combined with halogenation or charcoal
filtration (strength of recommendation[SOR]: C, based on expert opinion andmicrobiological testing). Halogenation alone(ie, chlorine and iodine) is not effective
against Cryptosporidium (SOR: C, based on
microbiological testing).

Clinical commentary
fast track

5 methods meet
EPA standards forlower pathogencounts under ideal
conditions:y BoilingyC hlorine dioxidetabletsy MIOX purifiery SteriPEN
y Filtration46

Why boil water when there areso many other options?
These days, “boil it, peel it, or forget it”
only goes so far with the unencumbered
traveler. Experience tells me that most hear
“Boil it” and instantly go right to “Forgetit!” Fortunately, there is an excellent
resource to assist patients in choosing
a personally acceptable portable water
purification system. It’s called the Water
Purification Database at usachppm.apgea.
army.mil/WPD/CompareDevices.aspx.1

z Evidence summary

With the rise in international travel andadventure sports, individuals are at increased risk of acquiring infections bydrinking water from impure water sources. Common waterborne infections thatback-country and international travelers
may contract include bacterial diarrhea,viruses, protozoa (such as Giardia andThis outstanding database was developedby an impartial third-party for the US Armyand gives clear, well-organized guidanceon over 60 purifiers. For each purifier,the guide covers efficacy against primarypathogens, purification mechanism, links
to manufacturers, and an advantages/disadvantages breakdown (such asweight, cost, and ease of use). Add thissite to your Internet “favorites” folder.
Timothy Mott, MD, FAAFPUS Naval Hospital, Sigonella, Italy

Cryptosporidium), and parasites (such asschistosoma). The risk of infection varies
based on travel location.
To prevent illness, travelers may
seek medical guidance regarding safe
water practice. In one study, 36% oftravelers sought advice from a physician
prior to international travel.2 Prevent-vol 57, No 1 / january 2008 The Journal of Family PracticetablePortable water purification: How do these 6 methods compare?
Method	Effectiveness	Advantages	Disadvantages

Boiling with cooling*

Kills viruses, bacteria, 	Simple, universally accepted,
protozoa, and parasites
no special equipment required

Time-consuming, may requirelarge amounts of fuel

Chlorine dioxide*

Kills bacteria, viruses, 	Same as chlorine/iodine
protozoa, and parasites
treatment but also treats		
Cryptosporidium, good		
palatability

Must wait up to 4 hours to treat
Cryptosporidium, costs more thaniodine/chlorine ($13 for 30 tabs)Chlorine/iodine

Does not kill Cryptosporidium,poor taste, must wait for water tobe treated; contraindicated inpregnancy, thyroid disease; notrecommended beyond few weeks
of useKills bacteria, viruses, protozoa
Inexpensive, easy, lightweight,(not Cryptosporidium), andtreats large quantities
parasites											Filtration†	Removes parasites, Giardia, 	Able to use water immediately, Can potentially be expensive,
Cryptosporidium, and bacteria
removes sediment, many have filters may clog easily, heavy, not		
combination of activated carbon, effective against small particle viruses,		
chemical disinfectant, or boththerefore should supplement with			chlorine or iodine

MIOX Purifier*Kills bacteria, viruses,	Light (8 oz), sturdy, treats large
protozoa, and parasites
quantities; requires camera		
batteries and salt			

Cost $130, must wait for 4 hours
and treat with higher strength to treat
Cryptosporidium; requires 30 minutes
to treat viruses, bacteria, and Giardia

UV light (SteriPEN)‡

Cost $100, does not work in turbid
conditions

Kills bacteria, viruses, protozoa, 	Light (8 oz), quick (treats 16 ozparasites in clear waterof water in 1 minute)* Meets EPA standards.
† Some filtration systems meet EPA standards. See chppm-www.apgea.army.mil/WPD/CompareDevices.aspx for testing resultsof individual filters.1‡ Meets EPA standards in clear water.

ing waterborne infections should be acomponent of traveler education, in addition to other standard advice, suchas mosquito avoidance and immunizations.3 (For more on travel safety, seethese Clinical Inquiries: “When shouldtravelers begin malaria prophylaxis?” inthe November 2007 Journal of Family
www.jfponline.com

Practice, pages 950–952, and “What is
the most effective and safe malaria prophylaxis during pregnancy?” on page 51of this issue.)
Which devices meet EPA standards?
The EPA has established a “minimalmicrobiological hazard” allowed for a
vol 57, No 1 / january 2008

47

Clinical Inquiries

fast track

The top 3
off-the-shelfdevices in US
Army tests were:yS weetWater
PurifieryM icropur MP 1tabletsy F irst Need
Deluxe purifier

48

portable water purification system tobe considered safe. Water purifiers must
reduce bacteria by 99.9999%, viruses by
99.99%, and protozoa (such as Cryptosporidium parvum) by 99.9% to receive
an EPA certification number.4
There are no head-to-head trials comparing the effectiveness of different methods of purification to prevent infectious
disease. The majority of the evidence isbased on data provided by manufacturers
to the EPA, with some independent studies
and expert opinion (Table ).
Expert opinion recommends bringing water to a rapid boil for at least
3 minutes and letting it cool as an effective means of water purification.5
Chlorine dioxide tablets, the MIOX purifier, and UV light (SteriPEN) have allmet EPA standards for lower pathogen
counts under ideal conditions. Halogenation does not reduce Cryptosporidium below the microbiological hazardof 99.9%, but it is generally acceptedto effectively treat viruses, bacteria, andother protozoa after filtering through acloth to remove large particles.6
Filtration with an absolute pore sizeof <0.1 micrometer (10 times smaller
than the EPA standard) has been generally accepted as effective against
protozoa and bacteria, but it is noteffective against viruses because of theirsmall size.7 When combined with either
halogenation or charcoal filters,
filtration can be effective against all
pathogens.8
Recommendations from others
The US Army Center for Health Promotion and Preventive Medicine (USACHPPM) published a report in 2006 on
the efficacy of commercial off-the-shelf
individual water purifiers.8 Using National Sanitation Foundation Protocol
P248 and applying it to “real-world”
emergency military operational conditions, USACHPPM found that no device
scored high on every attribute, and that
overall scores for most devices were inthe moderate range. The top score forany device was 79 (out of 100).8
The overall top 3 scoring products
were: 1) the SweetWater Purifier fromMountain Safety Research; 2) the Micropur MP 1 tablets from Katadyn North
America, Inc; and 3) the First Need
Deluxe water purifier from General Ecology, Inc. nAcknowledgments
The opinions and assertions contained herein are theprivate views of the authors and not to be construed
as official, or as reflecting the views of the US Air Force
Medical Service or the US Air Force at large.

References1.	Commercially available individual water purifiers.
Water Purification Database, US Army Center for
Health Promotion and Preventive Medicine Web
site. Available at: usachppm.apgea.army.mil/WPD/CompareDevices.aspx. Accessed on December 7,2007.
2.	Hamer DH, Connor BA. Travel health knowledge,attitudes and practices among United States travelers. J Travel Med 2004; 11:23–26.
3.	Hill DR, Ericsson CD, Pearson RD, et al. The Practice of Travel Medicine: Guidelines by the Infectious
Diseases Society of America. Clin Infect Dis 2006;
43:1499–1539.
4.	US Environmental Protection Agency: Guide Standard and Protocol for Testing Microbiological Water Purifiers: Report to Task Force. Cincinnati, OH:
US Environmental Protection Agency; 1987.
5.	Centers for Disease Control and Prevention. Watertreatment methods. Available at: wwwn.cdc.gov/travel/contentWaterTreatment.aspx. Accessed on
December 7, 2007.
6.	Gerba CP, Johnson DC, Hasan MN. Efficacy ofiodine water purification tablets against Cryptosporidium oocysts and Giardia cysts. Wilderness
Environ Med 1997; 8:96–100.
7.	Centers for Disease Control and Prevention, Division of Parasitic Diseases. Preventing Cryptosporidiosis: A guide to water filters and bottled water.
Available at: www.cdc.gov/ncidod/dpd/parasites/
cryptosporidiosis/factsht_crypto_prevent_water.
htm. Accessed on December 7, 2007.
8. 	Water Supply Management Program Project No.
31-EC-03E0. Performance and health risk assessment of commercial-off-the-shelf individual water
purifiers. Aberdeen Proving Ground, Md: US Army
Center for Health Promotion and Preventive Medicine; 2006. Available at: usachppm.apgea.army.
mil/WPD/PDFDocs/FinalReport.pdf. Accessed onDecember 7, 2007.

vol 57, No 1 / january 2008 The Journal of Family Practice