THE CYCLE OF EMERGING CONTAMINANTS
Susan T. Glassmeyer [EPA]

The use of the term “emerging” has led to a common misconception: that ECs are chemicals that have only recently
been released into the environment. In reality, these chemicals have likely been entering the environment as long as
they have been in use. What is “emerging” is the awareness in both the scientific community and general public that
these chemicals are being released into the environment through household wastewater, and can be detected in
water, sediment, soil and biota.

Excerpt; Water Resources IMPACT •  page 5, Volume 9 • Number 3                                                        May • 2007

The best wine is the oldest, the best water the newest.
William Blake (1757-1827)

For the past decade, so-called “emerging contaminants” (ECs) have become an increasing area of interest for
environmental research. This is because of concern about potential impacts of these chemicals on human health
and the environment. In 1998, there were approximately 100 papers published in the scientific literature on ECs.
In 2006, the number of papers increased to over 300, including a special issue dedicated to the topic in the journal
Environmental Science and Technology. But, what are these “emerging contaminants?” ECs are broadly defined
by the scientific community as pollutants that are currently not included in routine monitoring programs, and
which may be candidates for future regulation, depending on research on their toxicity, potential health effects,
occurrence in various environmental matrices, and public perception. The term has come to encompass a wide
variety of chemicals – pharmaceuticals and household chemicals such as fragrances, antimicrobials, surfactants,
and fluorescent whitening agents. Some definitions of ECs include newer classes of compounds, such
as nanomaterials and genetically modified food items. The majority of the ECs differ from the “conventional”
environmental pollutants, such as pesticides, metals, polycyclic aromatic hydrocarbons (PAHs), polychlorinated
biphenyls (PCBs), and dioxins because many ECs are used in typical households. The use of the term “emerging”
has led to a common misconception: that ECs are chemicals that have only recently been released into the
environment. In reality, these chemicals have likely been entering the environment as long as they have been in
use. What is “emerging” is the awareness in both the scientific community and general public that these chemicals
are being released into the environment through household wastewater, and can be detected in water, sediment,
soil and biota.

Recently, the practice of flushing unused or expired medications has come under scrutiny because pharmaceuticals
have been detected in wastewater treatment plant (WWTP) discharges. Several Federal agencies have
published guidelines advocating the disposal of unused medications in the trash, rather than the toilet,
to minimize their potential environmental impact (
http://www. whitehousedrugpolicy.gov/news/press07/
022007.html; http://www.fws.gov/news/NewsReleases/ showNews.cfm?newsId=708A991D-F915-7BD0-
085DE68425ABF68B).

In addition, some communities have begun working with local pharmacies on “take back” programs, as well as adding
pharmaceutical collections to their household hazardous waste collection programs. While these “take back” programs
have obstacles, particularly when dealing with pharmaceuticals  that have the potential for abuse, the efforts reflect the
growing awareness of the need to limit the environmental release of these chemicals.

The level of treatment that household wastewater receives varies throughout the United States (U.S.). Approximately
one-quarter of the homes in the U.S. use onsite septic systems to process household wastewater. These septic
systems depend on the homeowners’ diligence for maintenance, thus, treatment efficiency may decrease over time.
The remaining 75 percent of household wastewaters are discharged to municipal WWTPs. WWTPs are designed to
remove solid materials and reduce metal, bacteria, and other pathogen levels, but are not designed to specifically
destroy chemicals (see Figure 1 for a description of typical wastewater treatment processes). During wastewater
treatment, the solid materials are settled out, forming biosolids (commonly referred to as sludge). The concentrations
of several ECs have been measured in these biosolids. The concentrations are typically in the range of milligrams of
chemical per kilogram of biosolid, or parts per million (ppm). Biosolids can be incinerated, disposed of in landfills, or
spread on land as a fertilizer for agricultural crops or a soil amendment. These land applications potentially
allow the ECs to leach from the biosolids into the soil and surface and ground waters, depending on the fate and
transport properties of the chemicals. Human waste streams are not the only route of environmental introduction
for these chemicals. While this paper has primarily discussed the chemicals used in households, ECs also have
veterinary applications. Chemicals such as antibiotics and insecticides are often used in concentrated
animal feeding operations (CAFOs). The urine and feces from the animals can contain traces of these prophylactic
chemicals. As with human biosolids, if these wastes are not suitably contained, the ECs can seep from the
fecal material and enter the soil and surface and ground waters.

Returning to the WWTP process, after removing the solids, the liquid portion of the wastewater is further
subjected to disinfection to reduce the level of pathogens. The concentrations of ECs may be reduced, but are typically
not completely removed, by these steps. In a recent collaborative study between the U.S. Environmental Protection
Agency (USEPA) and the U.S. Geological Survey (USGS), the discharges from 11 WWTPs were examined
(Glassmeyer et al., 2005). Of the 110 chemicals that were tested, 68 were found in at least one effluent sample and
34 were found in at least half of the effluent samples.

Nine chemicals – including the fragrances benzophenone, ethyl citrate, galaxolide, tonalide and antimicrobial triclosan
– were found in every WWTP effluent sample. The number of chemicals found in any given effluent sample
ranged from 27 to 50; the median number of chemicals was 35. The concentrations of the ECs in these effluents
were typically in the high nanogram per liter (ng/L) to low microgram per liter (μg/L), or high parts per trillion (ppt)
to low parts per billion (ppb) range.

Through the effluent of WWTPs, outlets from individual septic systems, and runoff from land applied
biosolids, ECs can enter surface and ground waters. Because ECs have been measured in surface waters, there
are concerns regarding their impact on the environment. For example, some ECs can act as endocrine disrupting
chemicals (EDCs). EDCs have the potential to affect hormonal driven processes, such as reproduction. Aquatic
organisms are particularly susceptible to EDCs, because their entire life cycles are spent in continuous contact
with water. A variety of different physical, chemical, and biological processes, such as photolysis, hydrolysis,
biodegradation, volatilization, sorption, and simple dilution, work to decrease the concentration of ECs that are
ultimately detected in the water. These removal and transformation processes are compound-specific, and
some chemicals can remain at detectable levels miles downstream from their environmental introduction. In
the USEPA/USGS study, 54 of the 110 chemicals were detected in at least one sample downstream from the
WWTPs. However, there were fewer chemicals detected in the downstream samples, as compared to the effluent
samples. The numbers of chemicals detected ranged from 12 to 35 (median 24). The nine chemicals that were
found in every effluent sample were also less frequently detected in the downstream samples, decreasing from
100 percent to a range between 50 and 90 percent. The median concentrations of the chemicals in the downstream
samples similarly decreased. For the nine, the declines in median concentrations ranged from 44 to 86
percent.

Humans may also be exposed to ECs in the environment. Waters downstream of WWTP effluent outfalls, or
those receiving runoff from land where biosolids have been applied, may be used as source water for drinking
water supplies, and hence are potential routes of human exposure to ECs. Figure 1 depicts the processes that are
typically used in drinking water treatment. Several studies in Europe and the U.S. have examined the concentrations
of ECs in finished drinking water. For the chemicals that are detected, the concentrations are normally
less than 100 ng/L, with many of the detections reported at levels less than 10 ng/L. It should be noted that frequency
of detection of ECs in drinking water is far less than that found in surface water and wastewater, and
the concentrations in drinking water are a hundred to a thousand times lower.

While the disinfection steps in both drinking and wastewater treatment are primarily designed to remove
pathogens, they can also affect chemicals, forming disinfection by-products (DBPs). Researchers and regulators
are aware of formation of chemicals such as of formation of chemicals such as trihalomethanes (THMs) and haloacetic
acids (HAAs), and drinking water treatment plant operators are under strict rules to keep these chemicals to safe
levels. But the ECs may also be forming by-products. Laboratory studies have shown that several pharmaceuticals,
including acetaminophen, can become halogenated when treated with a chlorine disinfectant. Little is known about the
toxicity and the dose-responses of these by-products. Most of the published environmental monitoring studies only
report the removal rate of ECs during wastewater and drinking water treatment. These studies have not looked for,
and therefore have not found, any byproducts that may be forming during the disinfection process. To fully understand
the potential for human and environmental exposure to ECs, additional studies need to be conducted to determine the
concentrations of both the intact chemicals, as well as any metabolite and DBPs that may be formed during wastewater
and drinking water treatment processes. This information may assist state and federal regulators in deciding how to
improve the treatment of human and animal wastes and maintain a safe drinking water supply for the public.

Disclaimer: The U.S. Environmental Protection Agency through its Office of Research and Development funded and
managed the research described here. It has been subjected to Agency’s administrative
review and approved for publication. The conclusions and opinions drawn are solely those of the author and
should not be construed to reflect the views of the Agency. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.

REFERENCE
Glassmeyer, S.T., E.T. Furlong, D.W. Kolpin, J.D. Cahill, S.D.
Zaugg, S.L. Werner, M.T. Meyer, and D.D. Kryak, 2005. Transport
of Chemical and Microbial Compounds From Known
Wastewater Discharges: Potential for Use as Indicators of
Human Fecal Contamination. Environmental Science and
Technology 39(14):5157-5169.

Susan T. Glassmeyer
U.S. Environmental Protection Agency
26 W. Martin Luther King Dr., MS 564
Cincinnati, OH 45268
(513) 569-7526 / Fax: (513) 569-7757
glassmeyer.susan@epa.gov

Susan T. Glassmeyer is a Research Chemist in the
USEPA’s Office of Research and Development, National
Exposure Research Lab., Microbiological and Chemical
Exposure Assessment Research Div. in Cincinnati, Ohio.
She received a BS in Chemistry from Xavier University in
Ohio, and an MSES and PhD in Environmental Science
from Indiana University’s School of Public and Environmental
Affairs. Her research is focused in two areas: the
assessment of pharmaceuticals and other emerging contaminants
as indicators of human fecal contamination,
and the analysis of microorganisms, including Cryptosporidium
parvum, Giardia lamblia, and enterococci, by
mass spectrometry.
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