drugs in drinking water

One of those news items that tends to freak out the general public is the idea of pharmaceuticals and personal care products (e.g., shampoo) in our water supplies.  There’s birth control in the water!  There’s ibuprofen in the water!  There’s Prozac in the water!  Time to panic, indeed.  What the news media doesn’t report (and, I suspect, doesn’t understand) is that the concentrations we’re talking about here are low.  Reeeeaaallly low.  Let’s think about a generic liter of water (a liter is a little more than a quart, for the metrically challenged out there).  A generic liter of water weighs about 1 kg / 1000 g / 2.2 lbs.  In the environment, it could easily have 100 mg (0.1 g) of calcium carbonate dissolved in it.  Calcium and carbonate are considered major ions in drinking water.  More minor ions include chloride (about 9 mg per liter in my drinking water supply (0.009 g)) and fluoride, added for dental health (about 0.8 mg per liter – 0.0008 g).  The drinking water standard for lead, which is a known toxin, is 15 micrograms (ug) per liter (= 0.015 mg = 0.000015 g).

The levels of pharmaceuticals that are being detected in water sources are on the order of nanograms per liter.  That’s right, a one-thousandth of a microgram, a one-millionth of a milligram, a one-billionth of a gram, a one-trillionth of a kilogram.  Since that liter of water weighs a kilogram, we talk about ng per liter as “parts per trillion”.  Frankly it’s a modern miracle that we can even measure stuff at these trace levels, and the advances in aqueous analytical chemistry are the only reason we know that some of these compounds are out there in the environment.  (Side note: in true chemistry, there is no such thing as a concentration of “zero”.  Instead, concentrations are not detectable by current technology.)

Don’t let the small concentrations fool you — these compounds are able to do damage at these uber-trace levels…but so far we’ve only seen evidence of damage to fish and amphibians.  When you think about our lifestyles compared to those of fish and amphibians, it kind of makes sense — we’re not the ones constantly bathing in the water in question.  We spend an awful lot of time exposed to air rather than water.  So take a deep breath (no pharmaceuticals in the air, knock on wood) and keep drinking tap water.

This gets tricky when it comes to regulations.  EPA is charged with protection of “navigable waters” under the Clean Water Act, and generally has developed standards for tap water and treated wastewater that protect human health and, to a lesser extent, the environment.  The Clean Water Act itself was born from environmental disasters like the Cuyahoga river catching fire and giant foam piles in rivers and lakes, but most of today’s regulations are about people, a subject most of us can agree upon.  I think it would be a striking development for EPA to begin regulation of trace levels of pharmaceuticals for the protection of aquatic life — there are plenty of non-environmentalists who couldn’t care less about some transgender frogs but sure do care a lot about their water and wastewater bills.

The main solution to these trace contaminants is additional wastewater treatment, whether at a treatment plant or in a septic system, since these point sources are the largest entry point for these compounds into the water supply.  Drugs are designed to deliver the target dose into the body, assuming some fraction of the active ingredient will not be absorbed by the body and will pass through to wastewater.  I don’t think we would ever decide to take lower doses of drugs to protect the environment (again, your cancer or a transgender frog?  I’d probably vote for your cancer, too).  In an odd development, I appear to be advocating for UV treatment of wastewater, once again.  (I did not see that coming, for the record.)

So what’s the conclusion?  Trace levels of pharmaceuticals are out there, but they aren’t high enough to affect human health.  They are high enough to affect fish and amphibians, and it will be interesting to see if EPA develops wastewater discharge limits to protect aquatic life from these compounds.

One thought on “drugs in drinking water

  1. Hey Claire!

    Your blog is fantastic, thank you for doing what you do! Your writing is exceptional and really interesting to read. This post is particularly pertinent. It is an emerging issue that people are maybe overstating but I think is definitely worth monitoring.

    h2obig is a joint project that my friend Monique and I are only just starting. It would be great to trade emails with you (our email is info.h2obig@gmail.com) about your passions, what you see as the biggest challenges to water security, what interests you most in the water world etc etc. Basically we want to pick your brains!!

    We would appreciate any advice and/or wisdom that you have!

    Thank you and take care!!!
    Ariel and Monique, h2obig

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