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Chemical Marketplace: Shower at Your Own Risk?

by Bill Chameides | March 24th, 2011
posted by Erica Rowell (Editor)

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More than 80,000 chemicals are produced,
used, and present in the United States. These are some of their stories.

Turns out that cleanliness might not be such a good idea after all.

Combing through the scientific literature last week, I came across a paper by Gemma Castano-Vinyals of the Center for Research in Environmental Epidemiology in Barcelona and co-authors. “Socioeconomic Status and Exposure to Disinfection By-products in Drinking Water in Spain,” published in the journal Environmental Health, reported that folks with higher levels of education may be exposed to higher levels of toxicants from tap water. Why? Because, in large part, they take more and longer showers.

The Chemical Marketplace
A series that looks at chemicals in everyday consumer products
     Aluminum and antiperspirants »
     BPAF »
     Dioxin and eggs »
     Flame retardants and pets »
     Fluoride and water »
     Formaldehyde and no-iron shirts »
     Insect repellents »
     Nanoparticles and food »
     PBDE and fire retardants »
     PFOA and popcorn »
     TDCPP and the air»
     Triclosan and toothpaste »
     Trihalomethanes (THM) and

I am pretty much nonplussed about the whole socioeconomic-education-showering differential part of the paper — the idea that if you’re well-educated you shower more. While the authors’ data seems to support this contention, I am skeptical.

For one, the bulk of the Spanish study’s participants were older males (average age of 65) with 30 percent of them illiterate and only 17 percent with a minimum education level of high school. These education levels are not very representative of similarly aged Americans’ levels (see here and here), and so I am not all that sure how applicable the authors’ results are for the United States.

Secondly, the data was segmented into folks who bathed for less than seven minutes a day and those who bathed for more than seven minutes a day, with seven minutes being the average. (If someone asked you how many minutes you showered per day, would you be able to give an answer correct to the minute?)

Essential — and Potentially Hazardous? — to Our Health

What did surprise me was the fact that showering can pose a significant threat to our health. Sure, I had known that the use of chlorine to decontaminate drinking water generates byproducts such as trihalomethanes (THM), which have been linked to an increased risk of several cancers (including bladder, rectal and colon) as well as possible adverse developmental and reproductive effects during pregnancy. And that is why, in part, I and so many others filter our tap water before drinking it.

But filtering tap water may not be enough. It turns out that THMs are volatile (they readily move from water into the air), and they are easily inhaled and absorbed by the skin. And so, when you take a shower you are exposing yourself to THM vapors (it’s a similar case but less so in a bath). The longer you shower (and the hotter the water), the greater the exposure. (And by the way, hanging out in a chlorinated swimming pool packs quite an exposure punch too. See here, here, and here.)

Don’t Throw the Bathing Out With the Bath Water

Before you panic and start eschewing the shower, you should note that the U.S. Environmental Protection Agency says there is no epidemiological data that demonstrates a causal link to a bad health endpoint from chlorination byproducts. And I highly doubt that any data exists linking length of showers with disease — unless perhaps if we’re talking about multiple-hour-long sojourns in the shower stall preferably with a friend. And before you start lobbying to get the chlorine out of your municipal water system don’t forget that there’s a reason for using it: clean drinking water is a fundamental component of our health.

However, if you’re concerned about exposure from bathing and you already filter your drinking water, maybe it’s time to add a comparable filter to your shower/bath or step up to a whole house filter.

Still, this has to give one pause. And speaking of pauses. Time for me to duck out. Got a meeting in an hour and still have not taken my morning shower.

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