H2O 911

Q&A

Rick Andrew, technical manager, Drinking Water Treatment Units, NSF International

Outpost: If a region you’re visiting has a communal water supply, can you count on it to be safe?

Rick Andrew: No, and China is a good example of why not. China is becoming more developed and you can stay in a nice hotel, but even there they say don’t drink the water. They do not treat the water to be at a potable level, and even if they treat it to potability at the water treatment plant, by the time it goes through the distribution system it’s been exposed to infiltration and other sources of contamination that render it unsafe… If you’ll be in an area where there’s livestock like cows and chickens, which are common sources of cryptosporidium, assume any water source in the vicinity is contaminated.

O: You’re talking about harmful micro-organisms, not chemical contaminants?

RA: The biggest concern [when travelling] is micro-organisms. They’re the ones that cause acute illness, like Montezuma’s revenge. Chemical contaminants tend to be chronic contaminants—drinking the water for a number of years on an ongoing basis could lead to chronic effects like cancer. But on a [trip], chemical contaminants are not going to kill you or cause an acute illness, unless it’s water you suspect has industrial pollutants in it, or something along those lines, and in that case I wouldn’t drink it at all.

O: How does NSF define purification of drinking water?

RA: Purification is rendering a microbiologically questionable water supply safe to drink… The EPA [US Environmental Protection Agency] has a specific definition of a water purifier. That definition speaks in terms of treatment of microbiological [contaminates], and it breaks them down into three categories: bacteria, viruses and protozoa [parasites], all three of which could make you sick. The EPA requires that devices be able to reduce the concentration of active organisms by logs. For bacteria, it is six logs, which means 99.9999 percent—that’s six nines; for viruses they require a four-log treatment, so it’s 99.99 percent; and for microbiological cysts [like giardia and crypto] they require a three-log reduction, which would be 99.9 percent.*

O: There’s a big difference with each additional nine. Why is that?

RA: [Bacteria] can be present in higher numbers than viruses and parasites in any given water source. And they have a low infectious dose, meaning it doesn’t take that many to make you sick. So a filter needs to remove 99.9999 percent of [bacteria]. That way you’re unlikely to be attacked by an infectious dose.

O: What do you think of devices that use ultraviolet light to purify water?

RA: I would have some concerns—if the water had some cloudiness to it, or turbidity, it might inhibit the UV radiation from reaching all of the water.

EXTRA, EXTRA

Be sure to pack the following, wherever your travels take you:

• Water bottle(s) for refilling at hostels, hotels, guest houses: be sure to ask if you can boil the water yourself and always let it cool before bottling; buy bottles at outdoor stores as they are more resilient with multi-use, and resist residue and odour. Vallely advises taking two bottles on any trip so you can be disinfecting one while drinking from the other.

• Test strips to check for residual levels of iodine, chlorine or chlorine dioxide in water after you’ve treated it; if no residual is present, water is not purified and more chemical must be added (always check again).

• Vitamin C tablets or flavoured crystals, to offset the taste of iodine or chlorine.

The How-To’s of Water Safety

• Boiling water: boil for five to seven minutes, since longer times cause evaporation; at higher altitudes boil longer (one minute more/500 feet); be sure receiving bottle is clean and dry so water is not re-contaminated.

• Contact time for purifiers is the minimum time a chemical needs to be in water for disinfection to occur: for bacteria and viruses, it’s at least 15 minutes, for some parasites it’s 30 minutes in warm water, but up to four hours in cold; cold or turbid (dirty/cloudy) water takes longer to disinfect; turbid or unfiltered water needs double or triple the dose of chemical than clear.

• To clean turbid water before purifying it (if you don’t have a portable), put a piece of cloth/coffee filter over top of a container, pass water through it, add purifier. • Iodine should not be used by pregnant women or people with thyroid problems.

• Purifiers: check if they follow EPA (US Environmental Protection Agency) guidelines or protocols (see Q&A above).

• Portable water filters: check label to verify pathogens it claims to filter; look for a filter pore size of at least one micron or less; some experts recommend 0.3 or 0.2 micron size filter to ensure maximum screening; keep intake hose (where raw water comes in) away from newly filtered water; use caution when cleaning contaminated filter.

• Don’t drink local tap water even if local people drink it. They’ve built up an immunity.

NOTE: This information is a guideline only. Always get individual medical advice or information from a qualified source before travelling. For in-country info on water quality, go to www.safewateronline.com. Portable filters sold at specialty outdoor stores offer a good range of quality and price. Chemical purifiers are sold at outdoor stores and pharmacies. *The EPA, NSF and Health Canada do not certify portable water filter systems, however, some manufacturers of water safety products grade to the EPA’s definition of water purification.

This entry was posted on Wednesday, July 23rd, 2008 at 2:06 pm and is filed under Health. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a comment, or trackback from your own site. Add to del.icio.us.