A U.S. Geological Survey team sampled the Potomac River's waters (part of a nationwide survey, 2003-2005) to check for nearly 300 new contaminants. Some information on what they found...

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• Organic Compounds in Potomac River Water Used for Public Supply Near Washington, D.C., 2003-05
  The U.S. Geological Survey published this fact sheet detailing their findings that 85 out of 277 manmade compounds were found at least once in water at the Washington Aqueduct. And of the 26 most commonly detected compounds, two-thirds were found in the treated water.
• Judy Denver
• Robert Lawrence
• Thomas Jacobus
• Linda Birnbaum

Judy Denver
U.S. Geological Survey

We were involved, as part of our national program, in a study here at the Potomac River, at the Washington Aqueduct water facility, to look at both source waters, which are just the waters coming straight out of the river, and then also to sample finished water that's gone through the treatment plant. This is part of a larger study that's taking place in several locations across the country from here to Boston, the Midwest, Texas, Oregon, to get a broad cross section of public water supplies from the ambient water here in the river to the treatment plant. ...

I don't think most people think about their drinking water coming from a river like the Potomac right here. Somebody else's wastewater may be up the river and then it becomes drinking water?

Oh, yes. The Potomac River … is over 11,000 square miles. It's a mix of forest, agriculture and urban land use, so there's sewage treatment outfalls up north; there's industrial outfalls; there's a lot of water coming off of forest, which is pretty clean. That's the majority of the land use. And there's a good bit of agricultural runoff during storms and also from groundwater input. ...

What did your study find in the Potomac in terms of standard contaminants and new contaminants?

… We also are looking at a broad range of chemicals to find out if they're there. Many of them aren't things we have standards for. They are organic, manmade chemicals, so it's good to find out if they're there, and we do have analytic techniques to do that now for many of those chemicals.

So what did you find?

... We found 85 of 277 compounds were detected once here in the Potomac River. ... Only 35 of those compounds were detected what we consider frequently, which was greater than 20 percent of the samples. There were a few that were detected year-around -- just a few. They were all detected at part-per-billion levels, which are generally lower than any health standards we have. So even though many compounds were detected, we didn't exceed any existing standards in this river.

Does that mean it's safe, or does that mean there just are no standards established and maybe we haven't looked at them closely enough?

About half of the compounds had some kind of guideline to compare to for human health, and they were below that. About half of them don't, so those are places ... where toxicologists need to do some more research. ...

What did you find in terms of the treatment plants along the Potomac here, particularly, say, the Washington Aqueduct?

We sampled the finished water at the Washington Aqueduct, and we found about two-thirds of the compounds we detected were still detected in finished water. There were a few that disappear altogether, and there were some that are probably created in treatment. ... They were all still below existing standards in the treated water, too. ...

[Did you find the same kinds of things in the other areas that were studied -- Colorado, Texas, Massachusetts, Indiana?]

… Yes, we see similar concentrations and similar-type chemicals in other areas.

And is this going to lead to further testing?

Yes. Now we've done nine sites, and USGS [U.S. Geological Survey] wants to do 30 by 2012 for these, so we have a really good preliminary assessment ... in many different river basins of different sizes with different land uses upstream of the intake.

Robert Lawrence
Johns Hopkins School of Public Health

The USGS study is an important contribution to our understanding of just how widespread these manmade compounds are in the water supply. ...

My response as a public health person is that we should take those USGS data and use them to inform the EPA [Environmental Protection Agency] in developing much more appropriate clean water standards, which up to this point have not included monitoring and measuring all these organic chemicals. ... Whenever you find trace amounts of that many chemicals in our water supply -- and we know that some of those chemicals, even at parts of 1 per million or 1 per billion, are physiologically active -- yes, that's a real cause of concern.

You said the EPA should get the information and start drafting things, but the EPA can take a decade to draft rules. Do we have an urgent problem here?

The urgency is in protecting the watershed of water systems for our great cities and rural areas as well. And unfortunately, we have not had a very effective cooperation either between states or within regions to do that. And protecting a watershed means not allowing these chemicals to get in the source water to begin with.

So that means banning the chemicals.

It means restricting their use, and in some cases, yes, we may have to ban them. If we found, for example, that a particular chemical is repeatedly linked with serious health consequences, whether endocrine disruption or causing cancer or causing some other problem like autism, then I think we would need a ban.

Most of these things, there is no detectable safe limit available. That's the frustrating part of it. We know that when you do a risk analysis of things that are parts per million, parts per billion, parts per trillion, that it is a continuous variable, so at some point you may have reduced the risk to the point where perhaps only 1 in 5 million exposed Americans will have a bad health consequence.

At that point, you have to have a political decision. What are the trade-offs? Are we willing to allow that level of risk in order to have this economic benefit, etc.? That debate needs to start.

Were you surprised by the findings of this USGS study, or did that fit with what you thought was probably going on?

I was surprised by the number of different compounds that were detectable. I knew we were swimming in a sea of chemical soup, but I didn't realize the soup was quite as concentrated as it is.

... Is there a danger that if a level of a particular compound were acceptable and another one were acceptable, that you start to put a bunch of them together and then that's no longer a safe level?

You put your finger on one of the real concerns about toxicology. It may be safe to have a little bit of compound A or a little bit of compound B, but when the two of them are together, there's synergism, and they become really deadly. Sorting that out from a data collection and epidemiologic analysis perspective is a really difficult thing to do, but we need to get on with it, because that's exactly the kind of concern when you have so many different compounds entering the human body. ...

If you're talking to a drinking-water system manager who says, "I'm following the EPA's instructions; we're holding down all the substances that the EPA has identified, and therefore your water is safe," do you buy that? Is the water safe?

The water is safe from a bacteriologic and parasite basis, maybe from a viral basis, but not from a chemical basis. ... We have no methods in place now to regulate the entry into the water system of endocrine disruptors. ...

Part of the dilemma is that there are so many of these compounds to try to evaluate, and the testing procedures are so expensive. It costs $800 to do a single test of a water sample or food sample or a blood sample from a patient for dioxin. At $800 a test, you cannot accumulate the kind of data that you need to make the scientific validation as firm as most skeptics ... will accept as proof.

Thomas Jacobus
General Manager, Washington Aqueduct

... How tough is the challenge just to keep up with all [the] new sources of pollutants?

Fortunately, the drinking-water process is very effective. It can remove particles. It can remove chemicals, organics, inorganics. It can disinfect and get rid of the microbial activity.

But it was designed for a water source where ... you had an idea of what was out there. But as new elements come in -- synthetics, herbicides, pesticides, pharmaceuticals --[and] enter the water stream in concentrations because of more advanced development, more human activity, more animal activity, more commercial activity, those things, as they get in the water, make it harder for us to do our job. There's no question about that.

You're just racing to keep up with the change?

Right, and the real challenge is to figure out what to do, because we know a lot about water treatment. The water treatment industry throughout the United States is just excellent, but the treatment process you use really has to match what it is you're trying to treat. ...

Today I drink the water with great confidence, because our water meets the regulations. But of course, the question is, do the regulations match the threat? For now I think they do, but there's this whole concept of emerging contaminants -- contaminants that we're learning even more about, we're able to see at lower concentration levels than we were able to measure before. And then the logical question is, what is the effect of those on the river, on the fish, the plant life, and then, eventually, as you use that water for drinking, on the humans? ...

You've been here how many years?

I've been here 15 years.

... Over that period of time, how often has whoever determines water-quality standards changed the standards and said: "Look, there are new chemicals out there. ... You've got to put new filters in"? ...

... Every couple of years, there are fundamental rule changes that change some aspect of the water treatment. They do that to be increasingly more protective of the public as they look at both acute possibilities and the long-term, chronic effects of exposure to water over a lifetime and knowledge of some of the chemicals that we put into the water. Even disinfection byproducts, which are created at very minute levels, we've changed the treatment to manage those. We're always evolving on a parallel track with the technology [not only] to be able to do things, but to determine what that technology ought to be to meet the public health.

So we've got EPA, but we also have the health component and the Centers for Disease Control. And all those people feed information in as we figure out what treatment do we need to put in place to create a water that is continuously healthful. …

Health experts, other people talk to us about tens of thousands of new chemicals being used in one industry or another, from personal health care to road construction to automobiles. How many of these tens of thousands of chemicals can your Washington Aqueduct scientists keep up with?

We keep up with all the regulated chemicals. … We test here in our laboratories and send out for a few others, about 350 different substances either physical, organic, inorganic, synthetics, those kind of things. And over the course of a year, we will conduct about 65,000 tests daily, weekly, monthly, on various frequencies, depending on what it is we're interested in looking at. We will evaluate that, and then we will report all that data back to the EPA. We report it to the public in a confidence report. ...

What about unregulated substances? That's the frontier.

And the problem is this: It's a science issue. How do you test for something if you don't have a test for it? One of the things that has to happen is you have to identify those exceptions, and then you have to create a laboratory method, so everybody can use the same method to get the same result.

[Did the results of the USGS survey at the Washington Aqueduct indicate to you that there's a problem?]

It's a problem that we need to figure out the dynamics of whether or not what gets through does have a human health effect. That's the issue that has to be determined. Yes, we can measure at very low levels these things do get through the treatment plant, but USGS, in their work, will tell you that they're not trying to determine what the efficacy of the treatment is; they're trying to determine what is out there.

And so then we will take that information -- "we," the nation, the international community -- will take that information and look at the health effects of that. First thing they ought to do is look at keeping it out of the water in the first place. Don't put the pills in the toilet to go to the river. Don't have the runoff from the cattle-feeding operations. Don't do all of those things. Be more careful. That's the easy part, because if you don't put it in the water, then you don't have to take it out.

But the quantities that we're dealing with, we don't know if those quantities are harmful. We don't think they are.

Linda Birnbaum
Director, National Institute of Environmental Health Sciences

When you looked at that list that [the USGS] found, were there chemical compounds in the Washington Aqueduct intake water that were of concern to you in terms of their potential impact on human health?

Are there chemicals of concern? Yes. ... In that specific study, what was reported has some chemicals that I would rather not see in the water.

But to the point where you're worried about human health, or is it just why take the risk?

I think at this point the levels are very, very low, so I don't have a great deal of concern that something needs to be done imminently, but it would certainly be nice to reduce what's getting into the water so that we can avoid human exposure.

Nice? Or safer? Or necessary?

It's a hard question. I think it would be important to try to prevent environmental chemicals from getting into our drinking-water supply. ...

Risk is related not only to hazard -- in other words, can they cause an effect? -- but also the issue of dose. You need enough exposure as well to the chemical. So there are very low levels present in the drinking water. ... People only drink this water a little bit at a time. They're not in it and exposed continuously 24 hours a day, seven days a week for their lifetime.

... Do you know what the safe levels are?

In most cases, we don't know what the safe levels are. And some of the new science is suggesting that levels that we used to think were safe may in fact not be safe.

For humans.

For humans. So we're finding in certain cases that much lower levels than we previously thought were a problem may in fact have the potential to harm at least some segment of the population. We're not all alike. There's differential genetic susceptibility between people. There's differential age susceptibility between people. Our susceptibility can be influenced not only by the environmental chemicals that we're exposed to but by the different foods that we eat, which can affect the way that our body handles some of these different chemicals. So you have a wide range in the susceptibility of the human population, and while you may not be susceptible to a certain exposure, maybe I will. ...

Is it alarmist for somebody to say they wouldn't be drinking this water based on the chemicals being in there?

I wouldn't raise the alarm. I think that the levels of the chemicals in the water are very, very low. I would like to see them continue to decrease. ... A couple of years ago, when lead was reported in the Washington drinking water, I'd be out there beating the drum, saying those levels are high enough that they could potentially cause problems. These levels are really very, very low. ... Very honestly, the levels of chemicals in our finished drinking water are much lower than the levels of chemicals you find in most bottled water that you buy in the grocery store.