Background: Chemicals, used everyday in homes, industry 

and agriculture, can enter the environment in wastewater. 

These chemicals include human and veterinary drugs (including 

antibiotics), hormones, detergents, disinfectants, plasticizers, 

fire retardants, insecticides, and antioxidants. To assess whether 

these chemicals are entering our Nation’s streams, the Toxic 

Substances Hydrology Program of the U.S. Geological Survey 

(USGS) collected and analyzed water samples from 139 streams 

in 30 states during 1999 and 2000. Streams were sampled that 

were considered susceptible to contamination from various 

wastewater sources, such as those downstream from intense 

urbanization or livestock production. Thus, the results of this study 

are not considered representative of all streams. 

Although each of the 95 chemicals is used extensively, there 

is little information about the extent or occurrence of many of 

these compounds in the environment. Some may be indicators 

of certain classes of contamination sources, such as livestock 

or human waste, and some have human or environmental 

health implications. The results of this study are a starting point 

for investigation of the transport of a wide range of organic 

wastewater contaminants in the Nation’s waters.

New laboratory methods were developed in several USGS 

research laboratories to provide the analytical capability to 

measure concentrations of 95 wastewater-related organic 

chemicals in water. Uniform sample-collection protocols and field 

and laboratory quality-assurance programs were followed to 

ensure that results are comparable and representative of actual 

stream conditions.

Pharmaceuticals, Hormones, and Other Organic Wastewater 

Contaminants in U.S. Streams

A recent study by the Toxic Substances Hydrology Program of the U.S. Geological Survey (USGS) shows that a broad range 

of chemicals found in residential, industrial, and agricultural wastewaters commonly occurs in mixtures at low concentrations 

downstream from areas of intense urbanization and animal production. The chemicals include human and veterinary drugs 

(including antibiotics), natural and synthetic hormones, detergent metabolites, plasticizers, insecticides, and fire retardants. 

One or more of these chemicals were found in 80 percent of the streams sampled. Half of the streams contained 7 or more 

of these chemicals, and about one-third of the streams contained 10 or more of these chemicals. This study is the first 

national-scale examination of these organic wastewater contaminants in streams and supports the USGS mission to assess 

the quantity and quality of the Nation’s water resources. A more complete analysis of these and other emerging waterquality issues is ongoing.

Household chemicals can enter streams through wastewater 

discharges. A wastewater treatment facility near Atlanta, 

Georgia, is shown above. (Photograph by Daniel J. Hippe, 

U.S. Geological Survey)

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet FS-027-02

June 2002

Pharmaceuticals, hormones, and other organic wastewater 

contaminants were measured in 139 streams during 1999 and 

2000.
Findings: One or more chemicals were detected in 80 percent of 

the streams sampled, and 82 of the 95 chemicals were detected 

at least once. Generally, these chemicals were found at very 

low concentrations (in most cases, less than 1 part per billion). 

Mixtures of the chemicals were common; 75 percent of the 

streams had more than one, 50 percent had 7 or more, and 34 

percent had 10 or more.

The most frequently detected chemicals (found in more than 

half of the streams) were coprostanol (fecal steroid), cholesterol 

(plant and animal steroid), N-N-diethyltoluamide (insect repellent), 

caffeine (stimulant), triclosan (antimicrobial disinfectant), tri 

(2-chloroethyl) phosphate (fire retardant), and 4-nonylphenol 

(nonionic detergent metabolite). Steroids, nonprescription drugs, 

and insect repellent were the chemical groups most frequently 

detected. Detergent metabolites, steroids, and plasticizers 

generally were measured at the highest concentrations.

Human and environmental effects: Knowledge of the potential 

human and environmental health effects of these 95 chemicals 

is highly varied; drinking-water standards or other human or 

ecological health criteria have been established for 14. Measured 

concentrations rarely exceeded any of the standards or criteria. 

Thirty-three are known or suspected to be hormonally active; 46 

are pharmaceutically active. Little is known about the potential 

health effects to humans or aquatic organisms exposed to the low 

levels of most of these chemicals or the mixtures commonly found 

in this study.

Significance of findings: This study suggests that mixtures of 

pharmaceuticals, hormones, and other wastewater contaminants 

can occur at low concentrations in streams that are susceptible 

to various wastewater sources. It provides methodology and 

guidance for future monitoring and assessment of these types 

of environmental contaminants, and establishes the needed 

foundation for setting priorities for further study of sources, 

pathways and effects.

Future directions: Further analyses of these data, including 

relationships to specific source types, are ongoing. The Toxic 

Substances Hydrology Program is conducting research on the 

occurrence of organic wastewater chemicals in susceptible wells 

and drinking-water sources across the nation; assessments of 

antibiotics and antibiotic-resistant bacteria; the identification of 

wastewater indicators; and the development of new laboratory 

analytical capabilities, including sediment and fish tissue.

Additional information: These findings are based on 

“Pharmaceuticals, hormones, and other organic wastewater 

contaminants in U.S. streams, 1999-2000: A national 

reconnaissance,” an article published in the March 15, 2002 issue 

of Environmental Science & Technology, v. 36, no. 6, pages 1202-

1211. Data are presented in a companion USGS report, “Waterquality data for pharmaceuticals, hormones, and other organic 

wastewater contaminants in U.S. streams, 1999-2000” (USGS 

Open-File Report 02-94). These and other reports, data, and 

maps can be accessed on the Internet at http://toxics.usgs.gov.

Herbert T. Buxton and Dana W. Kolpin

Steroids

Nonprescription drugs

Inseect repellent

Detergent metabolites

Disinfects

Plasticizers

Fire retardants

Antibiotics

Insecticides

PAHs

Hormones

Other prescription drugs

Antioxidants

Fragrances

Solvent

0

3.0

0.5

1.0

1.5

2.0

2.5

EXPLANATION

DETECTION FREQUENCY, IN PERCENT

89 81 74 69 66 64 60 48 45 44 40 32 29 27 24

TOTAL CONCENTRATION, IN MICROGRAMS PER LITER*

Minimum value

25th percentile

Median

75th percentile

Maximum value *Maximum values not shown:

Steroids: 18.3

Nonprescription drugs: 17.4

Detergent metabolites: 55.6

Plasticizers: 17.4

Antibiotics: 3.6

Fragrances: 4.3

Steroids, nonprescription drugs, and an insect repellent 

were the three chemical groups most commonly detected 

in susceptible streams. Detergent metabolites, steroids, 

and plasticizers generally were found at the highest 

concentrations.

Veterinary pharmaceuticals used in animal agriculture can 

enter streams through runoff or infiltration. A swine facility 

near the South Fork Iowa River, Iowa, is shown above. 

(Photograph by Doug Schnoebelen, U.S. Geological Survey)

Contact for additional information:

Herb Buxton

Toxic Substances Hydrology Program

412 National Center, 12201 Sunrise Valley Dr.

Reston, VA 20192