Sunday, April 20, 2008

What's in your water?

Bottled water has been taking a beating, rightly so, over the past several months for being unnecessary and profligate of resources - one liter of the precious bottled nectar requiring three liters to manufacture, not to mention the petrochemicals and energy that are also consumed in the process. And all for so little gain given the stricter quality control standards applied to tap water compared with the bottled variant, surprising as that may seem, especially in light of the marketing ploys of the bottling companies. Yet the perception is widely held that tap water in this country is unsafe, or at least something to be wary of. Dulcie tells of a nutty columnist in the Tribune that happily ignored her mother's headache (it proved to be the harbinger of a fatal stroke) while studiously avoiding the dreaded tap water at all cost.

Now the bottle is fighting back: huge front page story the other day in the Tribune about "contamination" in Chicago water. There has been quite a bit of chatter recently about pharmaceuticals building up in water supplies and how it is even possible to detect illegal drug use by monitoring the effluent. Traces of pharmaceuticals and other chemicals were detected in various tap water sources around Chicago, but not in any of the bottled water supplies that were tested.

Cause for concern? I think not. Of course the take-away will be people getting all concerned about the purity of their tap water, which may prompt them to do things like install extra filters or purchase bottled products instead. I think the only significance of this story is the amazing ability of modern analytical techniques to detect fantastically minuscule quantities, so that almost nothing can be considered pure any more on that scale of impurity. The contaminants, like acetaminophen for example, were detected at the level of about one part per trillion - 1 in 10^12. That is one million times more dilute than one part per million or 1 ppm, a level where you might have to be concerned, where the Safe Drinking Water Act sets its levels for contaminants.

There are very few people who would think twice about popping a 100 mg dose of acetaminophen for a headache (actually I think the typical tablet contains 200 mg). So I did a quick calculation to determine how much water I would need to drink to get my from that source. In order to obtain 100 mg of acetaminophen from the Chicago water supply I would need to drink 4 L (about 1 gallon) per day for 30,000 years, a shade over 300 lifetimes. So tell me, should I be concerned? Should you?

Of course we should be vigilant about the purity of water and in fact the cities in America do a very good job on that. It is important to monitor the presence of new impurities that don't fall under the umbrella of contaminants listed in the Safe Drinking Water Act. I'm not sure it serves a useful purpose to report it in such a way that gives the impression that there is something really to be concerned about in the water right now. So why plonk it on the front page?

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