Download This is by the way

Pharmaceuticals in Drinking Water: An Overview
By Steven Drangsholt, Lesley Leggett, Jennifer Parker,
Ching-Yu Peng, and Kelly Stumbaugh
Introduction
The extensive use and disposal of pharmaceuticals worldwide leads to their presence in
wastewater and surface water; eventually, pharmaceuticals find their way into drinking water
supplies. Researchers and scientists have detected prescription and over-the-counter (OTC)
drugs, antibiotics, and synthetic hormones in aquatic systems. Detection of these chemicals is
limited by current technology; low levels of many compounds are not detectable, but are likely to
occur in water. While the ecologic and human health effects of pharmaceuticals in aquatic
ecosystems and drinking water are not fully known, evidence suggests that chronic low-level
exposure may be harmful. Pharmaceutical residues in drinking water may cause effects such as
contributing to antibiotic resistance of human pathogenic bacteria, reproductive effects, and
increased cancer risk. Conventional drinking water treatment techniques are inefficient at
removing most pharmaceuticals; other available treatment options may be more effective.
Prescription and Over-the-Counter (OTC) Drugs
Every year, thousands of prescription and OTC drugs are used. Most are ingested and
metabolized by the body before being excreted to sewage. Unused or expired drugs are
commonly flushed down the toilet and enter sewage without being metabolized. There are
numerous classes of prescription and non-prescription drugs. Whether or not these compounds
reach water sources used for drinking water depends on several factors: stability,
biodegradability, and water solubility. While prescription and non-prescription drugs are
detected in sewage effluents and drinking water, these substances are found at low-levels.
Typical concentrations in the ng/L-g/L (ppt-ppb) range. A 2002 USGS study, which sampled
many U.S. streams, reported detection frequencies of 32% and 81% for prescription and nonprescription drugs, respectively (toxics.usgs.gov).
Prescription drugs used in high doses have a much higher probability of entering and
persisting in water sources. Blood lipid regulators are the most commonly and widely detected
prescription drugs in receiving waters. Due to the high doses used in humans (often grams per
day) there is very high input of blood lipid regulators into the environment. Clofibric acid is an
active metabolite of lipid regulators and is formed when the drug is metabolized within the body.
In Europe, this compound has been detected in groundwater (4 g/L), lakes (1-9 g/L), and in
drinking water (270 ng/L). The annual input into the North Sea has been estimated to be as
much as 50-100 tons (Daughton and Ternes, 1999). This compound is persistent in the
environment, which also contributes to its widespread detection (Daughton and Ternes, 1999).
Effects from exposure to clofibric acid at low levels in not known.
Other prescription drugs are known to cause reproductive, mutagenic, and teratogenic
effects in various aquatic organisms. Beta-blockers (anti-hypertensive drugs) produce the
metabolites metroprolol and propranolol, which have been detected in sewage effluents at
concentrations <0.2 g/L. Reproductive effects following exposure have been shown for both
crayfish and fiddler crabs. Antidepressants, which increase serotonin neurotransmission, also
cause negative effects on aquatic organisms. Male mussels were induced to spawn when
exposed to low concentrations of fluoxetine and fluoroxamine; the active ingredient in Prozac
and the active ingredient in Luvox, respectively. More alarming effects are associated with antitumor drugs, known as antineoplastics, used in chemotherapy. These drugs are alkylating agents
with the capability to cause mutagenic or teratogenic effects in any organism. Antineoplastics
2
have been detected in sewage effluent (17 ng/L) and are primarily found in hospital sewage
effluent. Many other prescription drugs may be important source water pollutants: antiepileptics,
impotence drugs, and tranquilizers (Daughton and Ternes, 1999). Potential human health effects
are not well understood, but the animal evidence suggests there may be cause for concern.
Non-prescription drugs are commonly detected in source water. Ibuprofen, the active
ingredient in Advil, is the second most commonly detected pharmaceutical in water samples.
Both ibuprofen and naproxen have been detected at levels >1 g/L in sewage effluent and at
lower concentrations in surface water. While these drugs are used at very high levels, they may
be less stable in the environment; photolysis can degrade ibuprofen. Acetaminophen is another
commonly used OTC drug and has been detected in sewage effluent at concentrations of 6 g/L.
It is not detected in drinking water, most likely, because it is efficiently removed during the
drinking water treatment process. Other non-prescription drugs that are highly prevalent in
sewage effluent are caffeine and nicotine (Daughton and Ternes, 1999). The effects of chronic
low-level exposure to drugs, whether prescription or over-the-counter, is unknown.
Antibiotics
As the quantity and distribution of antibiotic resistance genes increases in microbial
populations, attempts are being made to identify the factors contributing to the rapid spread of
resistance. Infiltration of antibiotics and other antimicrobials into the aquatic environment has
the potential to be a significant part of the resistance problem. Antibiotics have the opportunity
to enter water bodies and come in contact with bacteria through their direct release in sewage and
from animal wastes. Through drinking water, in particular, antibiotic residues are able to come
into direct contact with humans, which may be a cause for concern in terms of spreading
3
resistance genes to human bacterial flora. This action could have serious implications for
treating bacterial infections in the future.
A variety of antibiotics have been detected in wastewater effluents, surface waters, and
drinking source waters (Kolpin et al., 2002). Researchers have detected low level concentrations
of fluoroquinolone (Vieno et al., 2007), macrolide and quinolone antibiotics (Ye et al., 2006) in
finished drinking water despite the lack of research into the presence of antibiotics in drinking
water. Antibiotic resistance in bacteria is encouraged by the presence of low concentrations of
antibiotics (Jørgensen and Halling-Sørensen, 2000). Low doses allow the bacteria to survive in
the presence of antimicrobials without being eliminated; thereby, giving them the opportunity to
adapt and develop resistance. Though little is known about the causal connection between the
occurrence of resistant bacteria and the low environmental concentrations of antibiotics (Hirsch
et al., 1999), it is plausible that the presence of aquatic antibiotics would generate bacterial
resistance.
Synthetic Hormones and Other Endocrine Disrupting Chemicals
Concerns about trace levels of synthetic hormones and other endocrine disrupting
chemicals in the environment have increased because evidence of endocrine disruption has been
found in wildlife. In particular, aquatic wildlife that lives downstream of wastewater discharges.
This situation has translated into concerns about the possible human health effects of consuming
drinking water contaminated with trace levels of such hormones. Research has found endocrine
disrupting chemicals in aquatic systems worldwide. Though current human epidemiological data
is inconclusive (Falconer et al., 2006), it is plausible that health effects from trace levels of
hormones may exist based on the known health effects of these compounds found in animal
studies.
4
Endocrine disrupting chemicals fall into two broad classes: synthetic pharmaceutical
hormones (oral contraceptives, hormone replacement therapy drugs, and steroids) and
anthropogenic chemicals (pesticides, industrial chemicals, and manufactured plastics). Synthetic
pharmaceutical hormones enter wastewater after being metabolized by humans. Anthropogenic
chemicals enter aquatic systems though industrial point source discharges or indirect pathways.
In general, endocrine disrupting compounds are lipophilic; concentrations would be expected to
be reduced during water treatment processes through sorption (Daughton and Ternes, 1999).
However, concentrations of estrogens in wastewater, although reduced during treatment, can still
be found at detectable levels post-treatment (Falconer et al., 2006). The drinking water process
used will determine its removal efficiency.
Removal of Pharmaceuticals in Drinking Water
According to a recent studies, the conventional drinking water treatment processes (e.g.,
coagulation and sand filtration) that effectively reduce the amount of natural organic matter
(NOM) and turbidity were inefficient for the removal of pharmaceuticals found in the source
water (Vieno et al., 2007 and Kim et al., 2007). Coagulation and the subsequent sedimentation
eliminated pharmaceuticals by only 3%. Rapid sand filtration following coagulation and
sedimentation eliminated an additional 10% of the pharmaceuticals (Vieno et al., 2007).
According to present knowledge and available technology, oxidation by ozone,
adsorption to activated carbon (either powered or granular), and separation by membranes are the
most promising methods for the removal of pharmaceuticals (Vieno et al., 2007, Kim et al., 2007
and Stackelberg et al., 2007). Ozonation showed an average removal efficiency of 75%.
Removal efficacy is a function of the contaminant structure and ozone dose. When the ozone
dose was 1.0-1.3 mg/L of O3 (typical dose applied in drinking water treatments), it was
5
sufficiently high to remove most of the pharmaceuticals to below their limit of quantifications.
Ozone is a very selective oxidant and reacts preferentially with unsaturated bonds and aromatic
rings substituted by electron donor groups (e.g., OH, NH2, and OCH3). Amine functionalities are
structural components of many pharmaceuticals, such as beta blockers and fluoroquinolones
antibiotics, making these compounds highly reactive with ozone (Vieno et al., 2007).
The average removal efficiency of pharmaceuticals by granular activated carbon (GAC)
treatment is 75%. Removal capacity is limited by contact time, competition from natural organic
matter, contaminant solubility, and carbon type. During GAC filtration, adsorption occurs mainly
by hydrophobic interactions, but also ion exchange processes may take place. Adsorption
through hydrophobic interactions tends to increase with an increasing octanol-water partition
coefficient (Kow) value of a substance. The more hydrophobic pharmaceuticals have been
reported to be more efficiently eliminated by GAC filtration (Vieno et al., 2007 and Stackelberg
et al., 2007). Reverse osmosis (RO) and nanofiltration (NF) membranes provide effective
barriers for rejection of pharmaceuticals. Both RO and NF membrane processes showed
excellent removal rates (95%) for the pharmaceuticals (Kim et al., 2007).
Conclusions
Many classes of pharmaceuticals have made their way into water bodies worldwide.
Current exposure levels to humans via drinking water are not well characterized, but evidence
indicates that a variety of pharmaceuticals are present at low levels in drinking water.
Additionally, while the human health effects of drug residues in drinking water are not well
understood, animal studies suggest that these chemicals may be harmful to humans. Further
research is needed to better quantify the efficiency of different drinking water treatment methods
in order to reduce possible health hazards.
6
References
Daughton CD, and Ternes TA. Pharmaceuticals and personal care products in the environment:
agents of subtle change? Environmental Health Perspectives 1999, 107(6), 907-938.
Falconer IR, Chapman HF, Moore MR, Ranmuthagala G. Endocrine-disrupting compounds: a
review of their challenge to sustainable and safe water supply and water resuse.
Environmental Toxicology 2006, 10, 181-191.
Hirsch R, Ternes TA, Haberer K, and Kratz L. Occurrence of Antibiotics in the Aquatic
Environment. The Science of the Total Environment 1999, 225, 109-118.
Jørgensen, SE and Halling-Sørensen B. Drugs in the Environment. Chemosphere 2000, 40,
691-699.
Kim SD, Cho J, Kim IS, Vanderford BJ, and Snyder SA. Occurrence and removal of
pharmaceuticals and endocrine disruptors in South Korean surface, drinking, and waste
waters, Water Research 2007, 41, 1013-1021.
Kolpin DW, Furlong ET, Meyer MT, Thurman EM, Zaugg SD, Barber LB, and Buxton HT.
Pharmaceuticals, Hormones, and Other Organic Wastewater Contaminants in U.S.
Streams, 1999-2000: A National Reconnaissance. Environmental Science and
Technology 2002, 36, 1202-1211.
Stackelberg PE, Gibs J, Furlong ET, Meyer MT, Zaugg SD, and Lippincott RL. Efficiency of
conventional drinking-water-treatment processes in removal of pharmaceuticals and other
organic compounds. Science of the Total Environment 2007, 377, 255–272.
U.S. Geologic Survey. Pharmaceuticals, Hormones, and Other Organic Wastewater
Contaminants in U.S. Streams. USGS Fact Sheet FS-027-02, June 2002.
http://toxics.usgs.gov/pubs/FS-027-02/index.html.
Vieno NM, Härkki H, Tuhkanen T, and Kronberg L. Occurrence of pharmaceuticals in river
water and their elimination in a pilot-scale drinking water treatment plant. Environmental
Science and Technology 2007, 42, 5077-5084.
Ye Z, Weinberg HS, and Meyer MT. Trace analysis of trimethoprim and sulfonamide,
macrolide, quinolone, and tetracycline antibiotics in chlorinated drinking water using
liquid chromatography electrospray tandem mass spectrometry. Analytical Chemistry
2007, 79(3), 1135-1144.
7