Pharmaceuticals, hormones, and other organic wastewater contaminants in U.S. streams, 1999-2000: a national reconnaissance.

TL;DR: The U.S. Geological Survey used five newly developed analytical methods to measure concentrations of 95 organic wastewater contaminants (OWCs) in water samples from a network of 139 streams across 30 states during 1999 and 2000 as mentioned in this paper.

Abstract: To provide the first nationwide reconnaissance of the occurrence of pharmaceuticals, hormones, and other organic wastewater contaminants (OWCs) in water resources, the U.S. Geological Survey used five newly developed analytical methods to measure concentrations of 95 OWCs in water samples from a network of 139 streams across 30 states during 1999 and 2000. The selection of sampling sites was biased toward streams susceptible to contamination (i.e. downstream of intense urbanization and livestock production). OWCs were prevalent during this study, being found in 80% of the streams sampled. The compounds detected represent a wide range of residential, industrial, and agricultural origins and uses with 82 of the 95 OWCs being found during this study. The most frequently detected compounds were coprostanol (fecal steroid), cholesterol (plant and animal steroid), N,N-diethyltoluamide (insect repellant), caffeine (stimulant), triclosan (antimicrobial disinfectant), tri(2-chloroethyl)phosphate (fire retardant), and 4-nonylphenol (nonionic detergent metabolite). Measured concentrations for this study were generally low and rarely exceeded drinking-water guidelines, drinking-water health advisories, or aquatic-life criteria. Many compounds, however, do not have such guidelines established. The detection of multiple OWCs was common for this study, with a median of seven and as many as 38 OWCs being found in a given water sample. Little is known about the potential interactive effects (such as synergistic or antagonistic toxicity) that may occur from complex mixtures of OWCs in the environment. In addition, results of this study demonstrate the importance of obtaining data on metabolites to fully understand not only the fate and transport of OWCs in the hydrologic system but also their ultimate overall effect on human health and the environment.

Summary

Introduction

• The continued exponential growth in human population has created a corresponding increase in the demand for the Earth’s limited supply of freshwater.
• Household chemicals, pharmaceuticals, and other consumables as well as biogenic hormones are released directly to the environment after passing through wastewater treatment processes (via wastewater treatment plants, or domestic septic systems), which often are not designed to remove them from the effluent (2).
• Potential concerns from the environmental presence of these compounds include abnormal physiological processes and reproductive impairment (7-12), increased incidences of cancer (13), the development of antibiotic-resistant bacteria (14-17), and the potential increased toxicity of chemical mixtures (18).
• They represent a starting point for this investigation examining the transport of OWCs to water resources of the United States.
• This paper describes the analytical results available from 139 streams sampled during 1999-2000 .

Site Selection and Sampling

• Little data were available on the occurrence of most of the targeted OWCs in U.S. streams at the onset of this investigation.
• Therefore, the selection of sampling sites primarily focused on areas considered susceptible to contamination from human, industrial, and agricultural wastewater.
• The 139 stream sites sampled during 1999-2000 represent a wide range of geography, hydrogeology, land use, climate, and basin size.
• Water samples for each chemical analysis were stored in precleaned-amber, glass bottles and collected in duplicate.
• Samples collected in 1999 were analyzed for a subset of the OWCs based on the watershed land-use characteristics.

Analytical Methods

• To determine the environmental extent of 95 OWCs (Table 1) in susceptible streams, five separate analytical methods were used.
• Methods 1 and 2 process calibration standards through the extraction procedure, which generally corrects concentrations for method losses but not matrix effects.
• The laboratory blanks were used to assess potential sample contamination.
• Compounds that were measured by more than one analytical method also were used to evaluate the results for this study.

Results and Discussion

• One or more OWCs were found in 80% of the 139 streams sampled for this study.
• The presence of the parent compound and/or their select metabolites in water resources has previously been documented for OWCs (40, 41) as well as other classes of chemicals such as pesticides (42, 43).
• The data show two environmental determinations: frequency of detection and percent of total measured concentration for each group of compounds.
• SCIENCE & TECHNOLOGY 9 1209 Mixtures of various OWCs were prevalent during this study, with most (75%) of the streams sampled having more than one OWC identified.
• Thus, the results of this study suggest that additional research on the toxicity of the target compounds should include not only the individual OWCs but also mixtures of these compounds.

Acknowledgments

• The authors wish to acknowledge the USGS scientists and field technicians who provided essential assistance to this project by identifying candidate stream sites across the United States and in collecting and processing stream samples.
• In addition, the authors thank Michele Lindsey, Jeff Cahill, and Greg Brown for their important contributions to developing the analytical methods being used.
• The authors also acknowledge Steffanie Keefe for her efforts in compiling the existing ecotoxicological data, Jessica Hopple for her assistance in generating select figures for this paper, and Kymm Barnes for her assistance in compiling the water-quality data for this study.
• This project was supported by the U.S. Geological Survey, Toxic Substances Hydrology Program.
• The use of trade, firm, or brand names in this paper is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.

Figures

TABLE 1. (Continued)

TABLE 1. (Continued)

FIGURE 5. Relation between total concentration (summation from all detections) and number of organic wastewater contaminants found per water sample (Spearman’s rank correlation coefficient ) 0.94, P < 0.001).

FIGURE 4. Frequency of detection of organic wastewater contaminants by general use category (4A), and percent of total measured concentration of organic wastewater contaminants by general use category (4B). Number of compounds in each category shown above bar.

FIGURE 1. Location of 139 stream sampling sites.

TABLE 2. Summary of Quality Assurance/Quality Control Results for Target and Surrogate Compoundsb

FIGURE 2. Measured concentrations for the 30 most frequently detected organic wastewater contaminants. Boxplots show concentration distribution truncated at the reporting level. Estimated values below the reporting level are shown. Estimated maximum values for coprostanol and cholesterol obtained from Method 5 (Table 1) are not shown. The analytical method number is provided (in parentheses) at the end of each compound name. An explanation of a boxplot is provided in Figure 3.

FIGURE 3. Comparison of concentrations of select compounds that were measured using two different methods with significantly different reporting levels. Boxplots show concentration distribution truncated at the reporting level. Estimated values below the reporting level are shown. Estimated maximum values for chloesterol and coprostanol obtained from Method 5 (Table 1) are not shown. The analytical method number is provided (in parentheses) at the end of each compound name.

Full text

University of Nebraska - Lincoln University of Nebraska - Lincoln
DigitalCommons@University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln
USGS Staff -- Published Research US Geological Survey
2002
Pharmaceuticals, Hormones, and Other Organic Wastewater Pharmaceuticals, Hormones, and Other Organic Wastewater
Contaminants in U.S. Streams, 1999-2000: A National Contaminants in U.S. Streams, 1999-2000: A National
Reconnaissance Reconnaissance
Dana Kolpin
U.S. Geological Survey
Edward Furlong
U.S. Geological Survey
Michael Meyer
U.S. Geological Survey
, mmeyer@usgs.gov
E. Michael Thurman
U.S. Geological Survey
Steven Zaugg
U.S. Geological Survey
See next page for additional authors
Follow this and additional works at: https://digitalcommons.unl.edu/usgsstaffpub
Part of the Earth Sciences Commons
Kolpin, Dana; Furlong, Edward; Meyer, Michael; Thurman, E. Michael; Zaugg, Steven; Barber, Larry; and
Buxton, Herbert, "Pharmaceuticals, Hormones, and Other Organic Wastewater Contaminants in U.S.
Streams, 1999-2000: A National Reconnaissance" (2002).
USGS Staff -- Published Research
. 68.
https://digitalcommons.unl.edu/usgsstaffpub/68
This Article is brought to you for free and open access by the US Geological Survey at DigitalCommons@University of
Nebraska - Lincoln. It has been accepted for inclusion in USGS Staff -- Published Research by an authorized
administrator of DigitalCommons@University of Nebraska - Lincoln.

Authors Authors
Dana Kolpin, Edward Furlong, Michael Meyer, E. Michael Thurman, Steven Zaugg, Larry Barber, and
Herbert Buxton
This article is available at DigitalCommons@University of Nebraska - Lincoln: https://digitalcommons.unl.edu/
usgsstaffpub/68

Pharmaceuticals, Hormones, and
Other Organic Wastewater
Contaminants in U.S. Streams,
1999-2000: A National
Reconnaissance
DANA W. KOLPIN*
U.S. Geological Survey, 400 S. Clinton Street, Box 1230,
Iowa City, Iowa 52244
EDWARD T. FURLONG
U.S. Geological Survey, Box 25046, MS 407,
Denver, Colorado 80225-0046
MICHAEL T. MEYER
U.S. Geological Survey, 4500 SW 40th Avenue,
Ocala, Florida 34474
E. MICHAEL THURMAN
U.S. Geological Survey, 4821 Quail Crest Place,
Lawrence, Kansas 66049
STEVEN D. ZAUGG
U.S. Geological Survey, Box 25046, MS 407,
Denver, Colorado 80225-0046
LARRY B. BARBER
U.S. Geological Survey, 3215 Marine Street,
Boulder, Colorado 80303
HERBERT T. BUXTON
U.S. Geological Survey, 810 Bear Tavern Road,
West Trenton, New Jersey 08628
To provide the first nationwide reconnaissance of the
occurrence of pharmaceuticals, hormones, and other
organicwastewatercontaminants(OWCs)inwaterresources,
the U.S. Geological Survey used five newly developed
analytical methods to measure concentrations of 95 OWCs
in water samples from a network of 139 streams across
30 states during 1999 and 2000. The selection of sampling
sites was biased toward streams susceptible to contami-
nation(i.e.downstreamofintenseurbanizationandlivestock
production). OWCs were prevalent during this study,
being found in 80% of the streams sampled. The compounds
detected represent a wide range of residential, industrial,
and agricultural origins and uses with 82 of the 95
OWCs being found during this study. The most frequently
detected compounds were coprostanol (fecal steroid),
cholesterol (plant and animal steroid),
N
,
N
-diethyltoluamide
(insectrepellant),caffeine(stimulant),triclosan(antimicrobial
disinfectant), tri(2-chloroethyl)phosphate (fire retardant),
and4-nonylphenol(nonionicdetergentmetabolite).Measured
concentrations for this study were generally low and
rarely exceeded drinking-water guidelines, drinking-water
healthadvisories,oraquatic-lifecriteria.Manycompounds,
however, do not have such guidelines established. The
detection of multiple OWCs was common for this study, with
a median of seven and as many as 38 OWCs being
found in a given water sample. Little is known about the
potential interactive effects (such as synergistic or
antagonistic toxicity) that may occur from complex mixtures
of OWCs in the environment. In addition, results of this
study demonstrate the importance of obtaining data on
metabolitestofullyunderstandnotonlythefateandtransport
of OWCs in the hydrologic system but also their ultimate
overall effect on human health and the environment.
Introduction
Thecontinuedexponentialgrowthinhumanpopulationhas
created a corresponding increase in the demand for the
Earth’s limited supply of freshwater. Thus, protecting the
integrity of our water resources is one of the most essential
environmental issues of the 21st century. Recent decades
have brought increasing concerns for potential adverse
human and ecological health effects resulting from the
production, use, and disposal of numerous chemicals that
offer improvements in industry, agriculture, medical treat-
ment, and even common household conveniences (1).
Research has shown that many such compounds can enter
the environment, disperse, and persist to a greater extent
than firstanticipated. Somecompounds, suchas pesticides,
are intentionallyreleased in measuredapplications. Others,
suchasindustrialbyproducts,arereleasedthroughregulated
and unregulated industrial discharges to water and air
resources.Householdchemicals,pharmaceuticals,andother
consumables as well as biogenic hormones are released
directlytotheenvironment afterpassingthroughwastewater
treatment processes (via wastewater treatment plants, or
domestic septic systems), which often are not designed to
remove them from the effluent (2). Veterinary pharmaceu-
ticals used in animal feeding operations may be released to
the environment with animal wastes through overflow or
leakage from storage structures or land application (3). As
a result, there are a wide variety of transport pathways for
many different chemicals to enter and persist in environ-
mental waters.
Surprisingly, little is known about the extent of environ-
mental occurrence, transport, and ultimate fate of many
synthetic organic chemicals after their intended use, par-
ticularly hormonally active chemicals (4), personal care
products,andpharmaceuticalsthataredesignedtostimulate
a physiological response in humans, plants, and animals (1,
5). One reason for this general lack of data is that, until
recently, there have beenfew analytical methods capable of
detecting these compounds at low concentrations which
mightbeexpectedintheenvironment(6).Potentialconcerns
from the environmental presence of these compounds
include abnormalphysiological processes andreproductive
impairment (7-12),increased incidencesof cancer(13), the
development of antibiotic-resistant bacteria (14-17), and
the potential increased toxicity of chemical mixtures (18).
For many substances, the potential effects on humans and
aquatic ecosystems are not clearly understood (1, 2, 19).
The primary objective of this study is to provide the first
nationwidereconnaissanceoftheoccurrenceofabroadsuite
of 95 organic wastewater contaminants (OWCs), including
* Correspondingauthorphone: (319)358-3614;fax: (319)358-3606;
e-mail: dwkolpin@usgs.gov.
Environ. Sci. Technol.
2002,
36,
1202-1211
1202
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 36, NO. 6, 2002 10.1021/es011055j Not subject to U.S. copyright. Publ. 2002 Am. Chem.Soc.
Published on Web 03/13/2002

many compounds of emerging environmental concern, in
streamsacrosstheUnitedStates.TheseOWCsarepotentially
associated with human, industrial, and agricultural waste-
waters and include antibiotics, other prescription drugs,
nonprescription drugs, steroids, reproductive hormones,
personalcare products,productsof oiluseand combustion,
andotherextensivelyusedchemicals.ThetargetOWCswere
selectedbecausetheyareexpectedtoentertheenvironment
through common wastewater pathways, are used in signifi-
cant quantities, may have human or environmental health
implications, are representative or potential indicators of
certain classes of compounds or sources, and/or can be
accurately measured in environmental samples using avail-
able technologies. Although these 95 OWCs are just a small
subset of compounds being used by society, they represent
astartingpointforthisinvestigationexaminingthetransport
of OWCs to water resources of the United States.
This paperdescribes the analytical resultsavailable from
139streamssampledduring1999-2000(Figure1).Theresults
areintendedtodetermineifOWCs areenteringU.S.streams
and to estimate the extent of their co-occurrence in sus-
ceptiblewaters.In addition,this studyprovides afocal point
for the development and testing of new laboratory methods
formeasuringOWCs inenvironmentalsamplesattracelevels,
an interpretivecontext forfuture assessmentsof OWCs,and
a means for establishing research priorities and future
monitoring strategies. More complete interpretations, in-
cluding an evaluation of the role of potential sources of
contamination, will follow in subsequent papers.
Site Selection and Sampling
Little data were available on the occurrence of most of the
targeted OWCs in U.S. streams at the onset of this investiga-
tion. Therefore, the selection of sampling sites primarily
focused on areas considered susceptible to contamination
from human, industrial, and agricultural wastewater. The
139 stream sites sampled during 1999-2000 (Figure 1)
represent a wide range of geography, hydrogeology, land
use, climate, and basin size. Specific information on the
individual sampling sites is provided elsewhere (20).
All samples were collected by U.S. Geological Survey
personnel using consistent protocols and procedures de-
signedtoobtainasamplerepresentativeofthestreamwaters
usingstandard depthand widthintegrating techniques(21).
At each site, a composite water sample was collected from
about 4-6 vertical profiles which was split into appropriate
containers for shipment to the participating laboratories.
For those bottles requiring filtration, water was passed
through a 0.7 µm, baked, glass-fiber filter in the field where
possible, or else filtration was conducted in the laboratory.
Water samples for each chemical analysis were stored in
precleaned-amber, glass bottles and collected in duplicate.
The duplicate samples were used for backup purposes (in
case of breakage of the primary sample) and for laboratory
replicates. Following collection, samples were immediately
chilledandsenttothelaboratory.Tominimizecontamination
of samples, use of personal careitems (i.e. insect repellents,
colognes,perfumes),caffeinatedproducts,andtobaccowere
discouraged during sample collection and processing.
Each stream site was sampled once during the 1999-
2000 study period. Samples collected in 1999 were analyzed
for a subset of the OWCs based on the watershed land-use
characteristics. Samples collected in 2000were analyzed for
the complete suite of OWCs. The analytical results for each
stream sample are available elsewhere (20).
Analytical Methods
To determine the environmental extent of 95 OWCs (Table
1) in susceptible streams, five separate analytical methods
were used. Each method was developed independently in
different laboratories, with somewhat different data objec-
tives, such as identifying hormones versus identifying
antibiotics. As a result of these differing objectives, varying
approaches were used in the development of the five
analytical methods. For example, select methods (Methods
1-3 below) used filtered water for solid-phase extraction
(SPE) with liquid chromatography/mass spectrometry posi-
tive-ion electrospray (LC/MS-ESI(+)) analysis, while others
(Methods 4 and 5 below) used whole-water continuous
liquid-liquid extraction (CLLE) with capillary gas chroma-
tography/mass spectrometry (GC/MS) analysis.
All methods use selected ion monitoring (SIM) for
improved sensitivity, thus, only the target compounds were
reported with no attempt to report data for nontarget
FIGURE 1. Location of 139 stream sampling sites.
VOL. 36, NO. 6, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
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TABLE 1. Summary of Analytical Results of Streams Sampled for 95 Organic Wastewater Contaminants
i
chemical (method) CASRN
N
RL
(µg/L)
freq
(%)
max
(µg/L)
med
(µg/L) use
MCL or
HAL
(
23
)
(µg/L)
lowest LC
50
for the
most sensitive
indicator species
(µg/L)/no. of aquatic
studies identified (
24
)
Veterinary and Human Antibiotics
carbodox (1) 6804-07-5 104 0.10 0 ND ND antibiotic --/1
chlortetracycline (1) 57-62-5 115 0.05 0 ND ND antibiotic - 88000
a
/3
chlortetracycline (2) 57-62-5 84 0.10 2.4 0.69 0.42 antibiotic - 88000
a
/3
ciprofloxacin (1) 85721-33-1 115 0.02 2.6 0.03 0.02 antibiotic --/0
doxycycline (1) 564-25-0 115 0.1 0 ND ND antibiotic --/0
enrofloxacin (1) 93106-60-6 115 0.02 0 ND ND antibiotic - 40
b
/29
erythromycin-H
2
O (1) 114-07-8 104 0.05 21.5 1.7 0.1 erythromycin
metabolite
- 665000
b
/35
lincomycin (1) 154-21-2 104 0.05 19.2 0.73 0.06 antibiotic --/0
norfloxacin (1) 70458-96-7 115 0.02 0.9 0.12 0.12 antibiotic --/6
oxytetracycline (1) 79-57-2 115 0.1 0 ND ND antibiotic - 102000
a
/46
oxytetracycline (2) 79-57-2 84 0.10 1.2 0.34 0.34 antibiotic - 102000
a
/46
roxithromycin (1) 80214-83-1 104 0.03 4.8 0.18 0.05 antibiotic --/0
sarafloxacin (1) 98105-99-8 115 0.02 0 ND ND antibiotic --/0
sulfachloropyridazine (2) 80-32-0 84 0.05 0 ND ND antibiotic --/0
sulfadimethoxine (1) 122-11-2 104 0.05 0 ND ND antibiotic --/5
sulfadimethoxine (2) 122-11-2 84 0.05 1.2 0.06 0.06 antibiotic --/5
sulfamerazine (1) 127-79-7 104 0.05 0 ND ND antibiotic - 100000
c
/17
sulfamerazine (2) 127-79-7 84 0.05 0 ND ND antibiotic - 100000
c
/17
sulfamethazine (1) 57-68-1 104 0.05 4.8 0.12 0.02 antibiotic - 100000
c
17
sulfamethazine (2) 57-68-1 84 0.05 1.2 0.22 0.22 antibiotic - 100000
c
/17
sulfamethizole (1) 144-82-1 104 0.05 1.0 0.13 0.13 antibiotic --/0
sulfamethoxazole (1) 723-46-6 104 0.05 12.5 1.9 0.15 antibiotic --/0
sulfamethoxazole (3) 723-46-6 84 0.023 19.0 0.52 0.066 antibiotic --/0
sulfathiazole (1) 72-14-0 104 0.10 0 ND ND antibiotic --/0
sulfathiazole (2) 72-14-0 84 0.05 0 ND ND antibiotic --/0
tetracycline (1) 60-54-8 115 0.05 0 ND ND antibiotic - 550000
b
/3
tetracycline (2) 60-54-8 84 0.10 1.2 0.11 0.11 antibiotic - 550000
b
/3
trimethoprim (1) 738-70-5 104 0.03 12.5 0.71 0.15 antibiotic - 3000
c
/4
trimethoprim (3) 738-70-5 84 0.014 27.4 0.30 0.013 antibiotic - 3000
c
/4
tylosin (1) 1401-69-0 104 0.05 13.5 0.28 0.04 antibiotic --/0
virginiamycin (1) 21411-53-0 104 0.10 0 ND ND antibiotic --/0
Prescription Drugs
albuterol (salbutamol) (3) 18559-94-9 84 0.029 0 ND ND antiasthmatic --/0
cimetidine (3) 51481-61-9 84 0.007 9.5 0.58
d
0.074
d
antacid --/0
codeine (3) 76-57-3 46 0.24 6.5 0.019 0.012 analgesic --/0
codeine (4) 76-57-3 85 0.1 10.6 1.0
d
0.2
d
analgesic --/0
dehydronifedipine (3) 67035-22-7 84 0.01 14.3 0.03 0.012 antianginal --/0
digoxin (3) 20830-75-5 46 0.26 0 ND
d
ND
d
cardiac stimulant - 10000000
a
/24
digoxigenin (3) 1672-46-4 84 0.008 0 ND ND digoxin metabolite --/0
diltiazem (3) 42399-41-7 84 0.012 13.1 0.049 0.021 antihypertensive --/0
enalaprilat (3) 76420-72-9 84 0.15 1.2 0.046
d
0.046
d
enalapril maleate
(antihypertensive)
metabolite
--/0
fluoxetine (3) 54910-89-3 84 0.018 1.2 0.012
d
0.012
d
antidepressant --/0
gemfibrozil (3) 25812-30-0 84 0.015 3.6 0.79 0.048 antihyperlipidemic --/0
metformin (3) 657-24-9 84 0.003 4.8 0.15
d
0.11
d
antidiabetic --/0
paroxetine metabolite (3) - 84 0.26 0 ND
d
ND
d
paroxetine
(antidepressant)
metabolite
--/0
ranitidine (3) 66357-35-5 84 0.01 1.2 0.01
d
0.01
d
antacid --/0
warfarin (3) 81-81-2 84 0.001 0 ND ND anticoagulant - 16000
c
/33
Nonprescription Drugs
acetaminophen (3) 103-90-2 84 0.009 23.8 10 0.11 antipyretic - 6000
a
/14
caffeine (3) 58-08-2 84 0.014 61.9 6.0 0.081 stimulant - 40000
e
/77
caffeine (4) 58-08-2 85 0.08 70.6 5.7 0.1 stimulant - 40000
e
/77
cotinine (3) 486-56-6 84 0.023 38.1 0.90 0.024 nicotine metabolite --/0
cotinine (4) 486-56-6 54 0.04 31.5 0.57 0.05 nicotine metabolite --/0
1,7-dimethylxanthine (3) 611-59-6 84 0.018 28.6 3.1
d
0.11
d
caffeine metabolite --/0
ibuprofen (3) 15687-27-1 84 0.018 9.5 1.0 0.20 antiinflammatory --/0
Other Wastewater-Related Compounds
1,4-dichlorobenzene (4) 106-46-7 85 0.03 25.9 4.3 0.09 deodorizer
75
1100
c
/190
2,6-di-
tert
-butylphenol (4) 128-39-2 85 0.08 3.5 0.11
d
0.06
d
antioxidant --/2
2,6-di-
tert
-butyl-1,4-benzoquinone (4) 719-22-2 85 0.10 9.4 0.46 0.13 antioxidant --/0
5-methyl-1H-benzotriazole (4) 136-85-6 54 0.10 31.5 2.4 0.39 antiocorrosive --/0
acetophenone (4) 98-86-2 85 0.15 9.4 0.41 0.15 fragrance - 155000
e
/21
anthracene (4) 120-12-7 85 0.05 4.7 0.11 0.07 PAH - 5.4
e
/188
benzo[
a
]pyrene (4) 50-32-8 85 0.05 9.4 0.24 0.04 PAH 0.2 1.5
a
/428
3-
tert
-butyl-4-hydroxy anisole (4) 25013-16-5 85 0.12 2.4 0.2
d
0.1
d
antioxidant - 870
c
/14
butylated hydroxy toluene (4) 128-37-0 85 0.08 2.4 0.1
d
0.1
d
antioxidant - 1440
a
/15
bis(2-ethylhexyl) adipate (4) 103-23-1 85 2.0 3.5 10
f
3
f
plasticizer 400 480
a
/9
bis(2-ethylhexyl) phthalate (4) 117-81-7 85 2.5 10.6 20
f
7
f
plasticizer 6 7500
a
/309
1204
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Frequently asked questions

Q1. What are the contributions in "Pharmaceuticals, hormones, and other organic wastewater contaminants in u.s. streams, 1999-2000: a national reconnaissance" ?

For example, Wolpin et al. this paper used analytical results from 139 streams sampled during 1999-2000 to determine if organic wastewater contaminants ( OWCs ) are entering U.S. streams and to estimate the extent of their co-occurrence in susceptible waters. 

Q2. What have the authors stated for future works in "Pharmaceuticals, hormones, and other organic wastewater contaminants in u.s. streams, 1999-2000: a national reconnaissance" ?

Future research will be needed to identify those factors ( i. e. high use and chemical persistence ) that are most important in determining the occurrence and concentration of OWCs in water resources. Furthermore, little is known about the potential interactive effects ( synergistic or antagonistic toxicity ) that may occur from complex mixtures of these compounds in the environment.