http://www.boston.com/dailyglobe2/154/science/Germs_can_lurk_in_water_bottles+.shtml

Germs can lurk in water bottles

By Cathryn M. Delude, Globe Correspondent, 6/3/2003

ummer's coming, and thoughts turn to the great outdoors. Before grabbing a water bottle and heading out, think about that bottle and how to keep its contents clean.

Water bottles are not all created equal. Soft plastic bottles bend and crinkle, giving bacteria a place to establish a beachhead, according to Ryan Jordan, a researcher at Montana State University's Center for Biofilm Engineering. Bottles made of hard, unbreakable Lexan plastic don't have that problem. Still, over time, bacteria from your mouth or the environment can grow in any bottle, especially if it contains sweet sports drinks or becomes warm.

No one has actually studied how many people get sick from water bottle bacteria, yet there are ample warnings about water-quality problems encountered by hikers in the back country. All streams and ponds are supposedly contaminated with microbes spread by wildlife, and humans and their animals. These microbes include giardia, fecal bacteria, and cryptosporidium, which cause various gastrointestinal problems such as diarrhea, cramping, and bloating.

To prevent diarrhea on the trail, hikers are warned to use water filters, which strip the microbes from the water, or iodine tablets, which kill many microbes (but not cryptosporidium). These warnings, however, are not based on scientific investigations about the actual risk of water-borne disease in the back country or the effectiveness of water-treatment methods on the trail, according to Jordan.

During the past two years, his research group decided to assess the water quality in streams and lakes at popular recreational areas, such as Yellowstone National Park and the Appalachian Trail, where they could expect to find bacterial contamination because of the numerous hikers. Indeed, they found that gastrointestinal problems are uncomfortably common on the trail. For example, of the 120 hikers who had been on the Appalachian Trail for three months or more that Jordan interviewed for his study, 90 percent had suffered gastrointestinal problems, and 20 percent had problems within the first week.

The prevalence of gastrointestinal infections among hikers might make it seem as though there were high levels of microbes swimming around in back-country water. On the contrary, Jordan found the water had very few microbes swimming about.

But the coating on rocks and sediment at the bottom of streams and ponds, as well as the thin surface film on standing water, did contain the usual suspects. These microbes grew in a slime, which scientists call a biofilm.

If you stir up the sediment or slurp in the surface film while filling your bottle, you gather biofilm clumps with your water. ''If a biofilm clump contains a thousand bacteria,'' Jordan explained, ''there's a much higher chance of getting sick than if you drank the same number of free-floating individual cells.'' By virtue of living together in large, attached groups, bacteria in biofilms become more virulent and resistant to the helpful bacteria in your gut that normally eliminate foreign intruders.

Biofilms can also foil trailside water-treatment efforts. Iodine tablets can't sterilize biofilms, and biofilms clog water filters.

In fact, all the hikers in Jordan's study who had been on the Appalachian Trail for three months or more had experienced filter failure. ''The common perception is that the water filters failed because they were plugged with sediments, and that certainly does happen,'' Jordan said. ''But we found failures even in Montana where we were filtering water from crystal-clear streams all summer. We discovered that the filters' performance degraded because we were filtering bacteria into them, and bacteria were growing biofilms on the filters. Eventually those biofilms plugged up the filters. That's a huge part of filter failure, one that's relatively unknown.''

Currently water filter manufacturers are not regulated, and they safety-test their own products. Because they don't understand biofilms, their tests may not cover the conditions people actually meet in the back country, Jordan said.

For hikers, Jordan recommends these ''best practices.'' To gather water, find a spot where you do not disturb the sediment, submerge your closed water bottle, open it under the surface, and let water flow in from the middle of the water column. Close the bottle underwater and lift it out. That way, you start with biofilm-free water, which you can filter for drinking.

To prevent biofilms from growing on the filter, back-flush the filter every few days to wash out the bacteria. Scrubbing the filter's outer element with a toothbrush is even more effective.

Jordan himself doesn't use filters. He relies on chlorine dioxide drops, which unlike iodine pills can kill giardia and cryptosporidium even in biofilms. (Chlorine dioxide has long been used in municipal water treatment, but is a relatively new product for back-country use.)

Surprisingly, the primary route of intestinal infection on the trail is not water, Jordan said, but rather the link between not washing hands after going to the bathroom, and handling food. He recommends alcohol hand gels rather than soap: ''Soap is too impractical to use properly and alcohol gels kill fecal bacteria more effectively.''

Back-country dishwashing can become very elaborate, but Jordan has these suggestions: Don't wash dishes! Just wipe them clean and dry them out. Bacteria can't live long on a dry surface, and putting them in the sun for an hour will disinfect them. Boiling water for your next freeze-dried meal will sterilize anything that's left in the cooking pot.

All the more time to lie back and enjoy the stars -- or whatever brought you so far from indoor plumbing to begin with.

This story ran on page C3 of the Boston Globe on 6/3/2003.
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