Do You Know What’s In Your Water?
BY STEVE HENTGES | MAY 3RD 2017 11:48 AM

It’s widely understood that a key reason why life developed on Earth is because ofwater. A common definition of a habitable environment is one in which plenty ofliquid water is available to sustain life. In short, we can’t live without water.
But there’s more to it than just the presence of water. We want our water to beclean and healthy so as to avoid risks to people and the environment fromunwanted contaminants. With that goal in mind, numerous environmental
monitoring studies have been conducted that look for various contaminants inwater, and generally find some at trace levels.
For practical reasons, most monitoring studies target only a limited number ofsubstances, meaning we only know what we looked for – not everything that might
be present. Although these studies provide quite a bit of data, that leaves a gap in
our understanding of the potential health and environmental impacts of real-life
chemical mixtures in water.
As a step towards addressing these limitations, the U.S. Geological Survey (USGS)
and the U.S. Environmental Protection Agency (EPA) recently conducted an indepth study to provide more insight into the complex mixtures of contaminantspresent in U.S. streams.
Based on what we know from previous studies it isn’t a surprise that contaminants
were found at low levels, but some of the findings may still be an eye-opener. For
example, of the 12 most frequently detected contaminants, all but three aresynthetic substances that were designed to be biologically active as pesticides orhuman drugs.

1/6Perhaps counterintuitively, contaminants that we frequently hear about may not be
commonly found in water. For example, bisphenol A (BPA), which is a synthetic
chemical that is primarily used to make polycarbonate plastic and epoxy resins, hasbeen a popular topic in the media for years.
Yet BPA was found only at very low levels, when detected at all, in less than 40% ofthe streams. Even at the highest level detected, which is well below 1 part perbillion, an adult would have to drink over 21,000 liters of water (over 5,600
gallons) per day just to reach the safe intake limit for BPA set by EPA. Obviously
that’s not even remotely possible, indicating that the amounts of BPA found are not
likely to be a human health concern.
To begin to get a handle on how these complex mixtures of chemicals may interact
with biological systems, the researchers also tested whole water samples in a seriesof screening tests to measure biological activity. With only one exception, all of the2/6

water samples tested positive for estrogenic activity, which was the most common
type of biological activity detected.
But this result too may be counterintuitive. The researchers reported that nearly
all of the observed estrogenic activity could be attributed to naturally producedhormones, in particular estrone, which is known to be a potent estrogen and is oneof the top 12 most frequently detected contaminants.
Conversely, even though BPA is known to be weakly estrogenic, BPA contributed
well under 1% of the observed estrogenic activity. Again, these results indicatethat BPA in water is not likely to be a human health concern.
Why Did USGS and EPA Do The Study And What Did They Do?
As noted by USGS and EPA, “[c]hemical-mixture exposures in streams are globalconcerns.” For that reason, hundreds of studies have been conducted by scientists
worldwide to measure levels of various contaminants in all types of water bodies(e.g., rivers, streams, lakes, oceans) as well as in potential sources ofcontaminants (e.g., wastewater treatment plants).
These studies document the presence of a wide variety of contaminants in water,
generally at very low levels. Both natural (e.g., human and animal hormones,
phytoestrogens) and synthetic (e.g., pharmaceuticals, pesticides, industrial
chemicals) substances are frequently found. For practical reasons though, moststudies typically target only a small number of substances.
While the resulting data is useful, it does not provide a complete picture. Morecomplete knowledge is needed to understand the full scope of contaminants inwater, the potential human and environmental health risks of these complex
mixtures, and to set priorities for the most appropriate actions to mitigate risks.
To begin to address the limitations of previous targeted studies, USGS and EPA
designed a study that combined two approaches to 1) measure levels of a wide
range of contaminants in water, 2) assess biological activity of the contaminant
mixtures, and 3) relate biological activity to the contaminants present. In the firstpart of the study, surface water from 38 streams nationwide was analyzed for 719
substances.

In the second part, biological activity of the water samples was3/6

monitored in four bioassays that measured estrogen, androgen and glucocorticoidactivity.
What Did They Find?
In short, they found a lot. All of the water samples contained at least one of thecontaminants and some contained as many as 162. Even the four streams fromundeveloped areas were found to contain some contaminants, although generally
fewer contaminants compared to streams in developed areas.
The type of contaminants found is particularly interesting. The twelve mostfrequently detected contaminants, found in 66-84% of the streams, are all ofanthropogenic origin, meaning they are the result of human activity.
Of these 12, all but three are synthetic substances that were designed to bebiologically active as pesticides or human drugs. Perhaps most strikingly, one of
the remaining three is estrone, which is a potent estrogenic hormone that isnaturally produced in the human body.
Overall, 57% of the 406 substances detected are synthetic substances designed tobe bioactive (e.g., pharmaceuticals, biocides). But bioactivity is not the exclusive
realm of synthetic substances. Along with estrone, naturally occurring
phytoestrogens, which are estrogenic compounds produced by plants, were also
commonly detected.
What Does It Mean?
The frequent detection of so many substances, in particular biologically activesubstances, may sound alarming. But low levels of a contaminant are notnecessarily a concern and frequency of detection is somewhat of an artefact of thehighly sensitive analytical methods that are available today. It’s not much of an
exaggeration to say that you will find almost everything if your analytical method is
sensitive enough.
Other factors beyond the level of a contaminant are critically important, inparticular biological potency. The case of BPA, which is well known to be weakly
estrogenic, is a good example. As reported by USGS and EPA, the estrogenic

4/6

potency of BPA is about 100,000 times less than the potency of estrone, which is aprototypical estrogen and was found at a higher frequency in this study.
As a result of its low potency, a typical adult weighing 70 kilograms (154 pounds)
would need to drink 21,472 liters (5,672 gallons) of water per day containing themaximum level of BPA detected (163 nanograms/L) just to reach the safe intake
level for BPA set by EPA. That’s especially not likely to happen since the maximum
level was found in water from the Chicago Sanitary and Ship Canal, which you’re
not likely to drink at all.
To provide more context for the health and environmental significance of thecontaminants, USGS and EPA went a step further to measure biological activity infour standard assays. The assays, which measure estrogenic, androgenic andglucocorticoid activity, do not directly evaluate health or environmental risks, but
provide information on the relative potential for risks. Importantly, the assays
were run on the whole water samples, which essentially evaluates the actual
chemical mixtures to which people or wildlife would be exposed from those watersamples.
Estrogenic activity was detected in all but one of the water samples, the only
exception being one of the streams from an undeveloped area, and the level ofestrogenic activity varied considerably. Although the assays only provide screening
data, some of the streams displayed estrogenic activity that is suggestive of risks toaquatic organisms, in particular fish.
But again, potency matters. As reported by USGS and EPA, estrogens naturally
produced by the human body (primarily estrone) could explain nearly all of theobserved estrogenic activity. Conversely, less than 1% of the estrogenic activity
could be explained by the presence of all other estrogenic compounds, only one ofwhich is BPA. Considering the low estrogenic potency of BPA, only a fraction ofthat 1% can be attributed to BPA.
A question not specifically addressed in the new study is where do thecontaminants come from? Although not within the scope of the research, anecdotal
evidence reported by USGS and EPA indicates that the samples with highest
biological activity were collected downstream of wastewater treatment plants that5/6

contributed a significant amount of the streamflow. That evidence is consistent
with other studies that report numerous contaminants in wastewater.
Once again, BPA is an informative example. Although BPA has been commonly
found in wastewater, many studies have also shown that BPA is readily biodegradedin wastewater treatment plants, which substantially reduces the amount of BPA
released to the environment from treatment plants. Some of those same studies
also show that many other contaminants are not efficiently degraded in today’s
treatment processes.
The new study suggests that more research is needed to better understand what
contaminants are in water and whether those complex mixtures pose any healthrisks. More importantly, the new data should help to focus further research and,eventually, help to prioritize actions to mitigate risks.

6/6