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ag_toxicity-6.pdf
IDAHO STATE UNIVERSITY
Toxicology of Silver Nanoparticles
Environmental Assessment CE4404
Kelli Seeliger
05/06/2013
This Document is the assessment of silver nanoparticles being released into the environment.
Table of Contents Purpose 2
History of Silver Use 3
Introduction of Silver IManoparticles 4
Uses of Silver Nanoparticles 9
Exposure Paths 11
Health Concerns for Plant Life 12
Health Concerns for Marine Life 14
Health Concerns for Human Life 15
Environmental Laws 17
Conclusion 20 '/
References 21
List of Figures
Figure 1: Nanomaterials dimensions on the metric scale (in nm)
Figure 2: Analysis of FIFRA registered products containing nanosilver
Figure 3: Silver killing Bacteria
Figure 4: Top-down and Bottom-up synthesis approaches
Figure 5: Representative TEM images of silver nanoparticles synthesized at various temperature
Figure 6: Green Synthesis of Silver Nanoparticles
Figure 7: Nanoparticle Surface Area to Volume ratio
Figure 8: Silver Nanoparticles in clothe
Figure 9: schematic of exposure in the environment
Figure 10: L. minor growth (dry weight) after exposure
Figure 11: Dose Response-Silver nanoparticles concentration and %mortality
Figure 12: A schematic of the human body with pathways of exposure to nanoparticles
Figure 13: Systemic Argyria of the skin from ingestion of colloidal silver
List of Tables
Table 1: Medical devices containing nanosilver
Page 1 of 21
Purpose /" ^ The purposes of this repoi^t itto make an assessment of the effects of placing silver
\_/
nanoparticles into a commercial washing machine. This report will discuss the history of silver
use and the purpose of using silvering nanoparticles. It will discuss the properties of silver
nanoparticles. The effects that silver nanoparticles have on marine life, plant ecosystem, as
well as the potential affects on human health will all be discussed. The Environmental Laws
affected by this project will be discussed as well. The report will go into the opposing views as
well as the supporting opinions. A conclusion will be found about whether the washing
machine should include the silver nanoparticles in the interior to help with odor and bacteria
eliminations.
Page 2 of 21
History of Silver Use The use of silver goes back centuries. Silver is one of the 'heavy metals', along with
lead, mercury, cadmium, and gold. Unlike the other heavy metals, silver in its pure form is non-
toxic to humans and animals. Historians believe that the ancient Macedonians covered wounds
l^r with silver plates to assist in the healing. The olden day Turkey, Anatolia, was the first known
region to mass-mine silver. Silver was used for cups and dishes in many European countries. It
was later found that having water in silver cups helps kill the bacteria that caused the bubonic
plaque.
Beginning around 900 B.C., the mines near Athens, Greece became the leading silver
producing mines for the Eastern Continents. They continued as such for many more years.
They seemed to recognizing the value of silver vessels in water purification and storage. Greek
craftsmen produced silver vessels for use on ships and for trade with other countries.
When the 'new world' was discovered and colonized Bolivia, Peru and Mexico produce
about 85 percent of the world's silver between 1500 and 1800 with an estimated total output
between 70K to 150K tons. In the 1700s, people started to discover the antibacterial qualities
of silver and applied them to their practice of medicine. They used silver nitrate to treat skin
ulcers, burns, compound fractures and infected wounds. ("The long history," )
It was more recently discovered that if you produce product that contaii^silver
nanoparticles, you get the same benefits of the pure silver without the cost of having a silver
product or coating the material with silver.
Page 3 of 21
Introduction of Silver Nanoparticles Nanoparticles are small particles between the size of 1 nm and 100 nm. "On December
3, 2003, President Bush signed into law the 21st Century Nanotechnology Research and
Development Act, which authorizes funding for nanotechnology research and development
(R&D) over 4 years, starting in Fiscal Year 2005. This legislation puts into law programs and
activities supported by the National Nanotechnology Initiative (NNI), one of the President's
highest multi-agency R&D priorities" ("21st century nanotechnology," 2003) As you can see in
Figure 2, the amount of Silver nanoparticles increases dramatically in 2003. r- ->
V
The Scale off Things - Nanometers and More Things Natural
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Things Manmade
Quantum corral of 48 iron atoms on copper surfaceoncopmrsurl positioned one at a timt with an STM tip
Corral diameter 14 nm
Figure 1: Nanomaterials dimensions on the metric scale (in nm) ("Scientific, technical, research,,")
Page 4 of 21
100 " NANOSI LVERs restored per year pel! axis)
Total AU. star woducfc registered (rigM as) Total NANOSILVER prnducls regaered (right am)
Ml registrants nano First NON-nanosil.fr
First silver registration (FIFRA) s nano
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Figure 2: Analysis of FIFRA registered products containing nanosilver ("Scientific, technical, research,,")
Silver is one of the most used nanoparticle in today's economy. Over 320 ton per year
of silver nanoparticles is produced and used worldwide. 30% of nanomaterial-containing
consumer products have claimed that they use silver nanoparticles.
In order to understand how silver nanoparticles work, you must understand what they are
working against and how. All bacteria use an enzyme referred to as a 'chemical lung' in order to
metabolize oxygen. Silver ions attacjvto the enzyme and keep it from obtaining oxygen. This
essentially suffocates any bacteria and leaves surrounding tissue or material unaffected.
Research to date has shown that bacteria have been unable to develop any immunity to silver.
Viruses grow by taking over another cell turning it into the virus. The silver ions stops oxygen 1 ̂
being brought into the virus-producing cell and it dies by suffocation. A fungus is composed of •
Page 5 of 21
a series of single cells. Each cell survives by means of a 'chemical lung' just like bacteria. The
silver ions disables the chemical lung and the fungus dies.
bacterium
bacterium docks and takes up Ag4
bacterium damaged or destroyed
on
Figure 3: Silver killing Bacteria (http://www.lintbells.com)
There are many different ways to synthesize silver nanoparticles. All the methods are
very similar; they just use different conditions or different reactants. The categories include
top-down, bottom-up, green, non-green, conventional, and a few others.
Top-down techniques use the generation of isolated atoms from the bulk materials
using different techniques. Methods include milling, attrition, repeated quenching are usually
involved in the top-down strategies. "Bottom-up method starts with a silver salt precursor that
Page 6 of 21
is reduced in a chemical reaction and the nanoparticles are formed through nucleation and
growth" ("Scientific, technical, research,,").
Physical methods:
•Photolithography
•Laser-beam processing
•Mechanical techniques (grinding and polishing)
0.1 nm 10 ran 100 nm 10pm 100 im
Bottom-up
Wet chemical methods:
•Organic synthesis
•Self assembly
•Colloidal aggregation
Figure 4: Top-down and Bottom-up synthesis approaches ("Scientific, technical, research,,") Synthesis approaches can be classified as either green or non-green. Green approaches
use environmentally safe components such as sugars and plant extracts to form and stabilize
nanosilver. The weakness of the green approaches is that there is less control over the process
of the produced nanosilver compared to the non-green methods.
Synthesis processes can be grouped as conventional and unconventional methods.
Conventional synthesis include the use of a two-phase systems, organic reducers, and inverse
micelles in the synthesis process. Unconventional methods include laser ablation methods,
radio catalytic methods, vacuum evaporation of metal etc. ("Scientific, technical, research,,")
Page 7 of 21
«PI
:n ^+]±9*m V.'***V *» •*•**••• •* 0
•v^^fefr•^••tim ^$$&
Figure 5: Representative TEM images of silver nanoparticles synthesized at various temperature and
reaction time: (a) 180 °C, 3 min; (b) 180 °C, 5 min; (c) 190 °C, 3 min; (d) 200 °C, 3 min. (Chen, 2007)
Figure 6: Green Synthesis of Silver Nanoparticles (Chen, 2007)
Page 8 of 21
Uses of Silver Nanoparticles When silver is turned into silver nanoparticles, the toxicity level increases. With silver,
antibacterial usefulness increases as particle size decreases because of the higher surface area
per unit volume. In the case of silver nanoparticles this allows them to easily interact with
other particles. This extra interaction gives them the extra antibacterial properties. Though, it
also increases their toxicity.
4-nm particle
50% of atoms on the surface
30-nm particle
- 5% of atoms on the surface
Figure 7: Nanoparticle Surface Area to Volume ratio.
Currently, Silver nanoparticles have various uses. The main use is for medical purposes. Silver
nanoparticles are in different types of creams. These are applied to skin conditions that include
infections, burns, and wounds. This helps kill bacteria in the skin. They also have catheters as well as
endotracheal tubes to help prevent bacteria and infections. Table 1 shows the various types of medical
devises that contain silver nanoparticles.
Silver nanoparticles are also used in clothes and textiles, most commonly socks and shirts. The
purpose of these items is to eliminate odors by using the antibacterial properties of silver nanoparticles
to kill the odor causing bacteria. Studies were done and that by the second washing, about 30% of the —- -
silver nanoparticles had been released and entered the groundwater.
Page 9 of 21
Table 1: Medical devices containing nanosilver Medical Domains Anesthesiology Cardiology
Nephrology Urology
Wound care
Examples Catheter for administration of local anesthetic (1) Battery used in implantable cardioverter-defibrillator (1)
Hemodialysis catheter (2) Urinary catheter (2) Battery used in implantable electrical pulse generator (1)
Burn and wound dressing, professional use (15) Burn and wound dressing, over the counter (2) Bum glove (1) Bum sock (1) Tubular stretch knit (1) (Adhesive) strip, professional use (2) (Adhesive) strip, over the counter (2) Gel(l) Compress (2) IV/catheter dressings (2)
BACTERIA
SILVER IONS
SILVER PARTICLES
SMARTSILVER ENHANCED SUBSTRATE
MOISTURE
Figure 8: Silver Nanoparticles in clothes (http://illumin.usc.edu/)
Silver Nanoparticles are also used in water purification. Many hospitals use water filters
that contain silver nanoparticles to help with MRSA and other various infections. There is also a
new ceramic filter being produced and studied. The ceramic coated with colloidal silver, which
is used for the antibacterial properties. Yakub et al. did a study on the adhesion of this porous
Page 10 of 21
ceramic material and E. coli. The results show that silver and colloidal silver coatings have the
strongest adhesion to E. coli, making it a good filter for E coli.
Some other various application include use for children toys, makeup, sunscreen,
condoms, Laundry Detergent, HEPA filter, among other things. The application this assessment
is most concerned with is in appliances. Silver Nano Health System is a patented application
released by Samsung in the mid 2000's. This system is an antibacterial technology that uses
silver nanoparticles inside various appliances that include washing machines, refrigerators, air
conditioners, air purifiers, and vacuum cleaners. Many of these appliances have a thin silver
nanoparticles coating on the interior.
Exposure Paths The production and use of silver nanoparticles are growing at an exponential pace. The
more that silver nanoparticles are used and produced, the high likelihood of the general public
has to be being exposed. The exposure paths can include through your skin from the textiles
and medical treatment, through ingestions of water, as well as through inhalation.
A q j f s
Figure 9: schematic of exposure in the environment. ("Scientific, technical, research,,")
Page 11 of 21
Health Concerns for Plant Life Gubbins et all did a study on silver nanoparticles and the effects on Lemna L. minor, or
Duckweed. There is currently so little known on how silver nanoparticles affect the
environment and more specifically, aquatic plants. The study looked into how silver at different
<JA concentrations affected plant growth. The results show that there was a slow in plant growth
^er^ over time with even a small concentration of 5 u.g/L. The effect grows as the concentration and
time exposed increases. A linear dose-response relationship after 14 d exposure was found.
This shows that silver nanoparticles may pose a significant risk to the environment. Duckweed
is an important food source to waterfowl as well as human in some cultures.
Page 12 of 21
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Figure 10: L. minor growth (dry weight) after exposure to A) NPlfor 7d, B) NPlfor 14d, C) NP2for7d, D)NP2for 14d, E)ionic silver for 7d, and F)ionic silver for 14d. (Gubbins, 2011)
A , •
Page 13 of 21
Health Concerns for Marine Life Many uses today of silver nanoparticles deals with the particles getting entered into the
groundwater and much marine life was being exposed to them. Still, there is not much known
about how the silver nanoparticles affect these animals. Bilberg et al performed a study on
zebra fish and their reaction to silver nanoparticles. This study dealt with the chemistry that
characterized PVP coated silver nanoparticles. A 48-hour study was done on the acute toxicity
of the nanosilver on the zebrafish. This was also compared to the toxicity of Silver Ions
(AgNOa). The zebra fish were given doses of 84 jUg/L of nanosilver and 25 jUg/L of silver ions.
The fish were observed every three hours for 48 hours. It was found that the fish has a
significant reduction in movement and also an increase of surface respiration. These symptoms
suggest a respiratory reaction. It was also found that silver nanoparticles have the chance of
becoming lethal to the zebrafish.
100
90
80
70
£ 60 x £ 50 -I n
c 40 ^
30
20
10
20 40 60 80 100 120 140 160
Silver nanoparticle concentration (^g L ~ ' )
Figure 11: Dose Response-Silver nanoparticles concentration and %mortality (Bilber, 201 1)
Page 14 of 21
Health Concerns for Human Life As discussed, silver nanoparticle uses have grown recently. This growth has had a direct
impact on the amount of silver nanoparticles that humans are subjected to.
NANOPARTICLES INTERNALIZED IN CELLS
Mithocotulrion
Nucleus
Cytoplasm •
Membrane •
Lipid vesicle
* Brain (neurological diseases: Parkinson's. Al^ieimer's disease)
\ Nanoparticle inhalation
I
Nanoparticles ingestion
Gastrointestinal system
(Crohit's disease, colon cancer)
Orthopedic implant' wear debris
(Auto-immune diseases, dermatitis, urticaria, vasculitis)
I Asthma, bronchitis, emphvsema, cancer)
'Circulatory lArtheriosderosis, vasoconstriction, system thrombus, high Unod pressure)
Heart inrryihmia. heart disease, death)
< disease of unknown Other organs
etiology in kidneys, liver)
•Lymphatic system Kaposi's sarcoma)
I I Auto-immune diseases. 'Skin dermatitis)
Figure 12: A schematic of the human body with pathways of exposure to nanoparticles ("Scientific, technical, research,,")
Various studies have been done to find the effects that silver nanoparticles have on humans.
OSHA has implemented the working environment limit value for a 40-hr/week exposure of 0.1
mg/m3 for metallic silver and 0.01 mg/m3 for soluble silver compounds being produced
(OSHA). It was shown that an over exposure to silver nanoparticles in the work environment
can cause adverse health effects that include respiratory and cardiovascular issues.
Some symptoms that have been found to be cause by silver nanoparticles are allergic
reactions from the silver build up in the body as well as Argyria. Argyria is a skin condition
caused by excessive exposure to silver. The symptoms are skin and organs that turns a
Page 15 of 21
bluish/grey color. Argyria has two types, generalized and local. Generalized occurs when there
is a long term build up of silver in the body and the discoloration is more extensive. Local
occurs when you are exposed to silver at a specific point of origin, like burn treatments.
("Argyria,")
Figure 13: Systemic argyria of the skin from ingestion of colloidal silver Silver nanoparticles are also known to build up in the liver as well as other organs like
the brain, respiratory system, and the kidney. There are symptoms believed to be related to the
exposure to silver nanoparticles, but there is not many studies to support that theory.
Page 16 of 21
Environmental Laws There are not many environmental laws and acts that regulate the production and use
of silver nanoparticles. The acts that do or could at some point affect silver nanoparticles
include The Clean Water Act (CWA), the Safe Drinking Water Act (SDWA), the Toxic Substance
Control Act (TSCA), and the Federal Insecticide Fungicide and Rodenticide Act (FIFRA).
Currently silver nanoparticles are being produced and used worldwide. There is no
requirement for any packaging to announce that there are silver nanoparticles present, there
for it makes it nearly impossible to track and regulate all consumer products using silver
nanoparticles.
The Clean Water Act
"The Clean Water Act (CWA) establishes the basic structure for regulating discharges of
pollutants into the waters of the United States and regulating quality standards for surface
waters. The basis of the CWA was enacted in 1948 and was called the Federal Water Pollution
Control Act, but the Act was significantly reorganized and expanded in 1972. "Clean Water Act"
became the Act's common name with amendments in 1972.
Under the CWA, EPA has implemented pollution control programs such as setting wastewater
standards for industry. We have also set water quality standards for all contaminants in surface
waters." ("Clean water act," 1972) It is very difficult for The CWA to regulate the release of
silver nanoparticles into the environment. It is doable at the production sites for silver
nanoparticles. With many of the new applications like textiles and washing machines, there is
not an easy way to quantify the amount being released.
Page 17 of 21
The Safe Drinking Water Act
"The Safe Drinking Water Act (SDWA) is the main federal law that ensures the quality of
Americans' drinking water. Under SDWA, EPA sets standards for drinking water quality and
oversees the states, localities, and water suppliers who implement those standards.
SDWA was originally passed by Congress in 1974 to protect public health by regulating the
nation's public drinking water supply. The law was amended in 1986 and 1996 and requires
many actions to protect drinking water and its sources: rivers, lakes, reservoirs, springs, and
ground water wells" ("Safe drinking water," 1974). If Silver nanoparticles are found to have a
negative effect on human health by the EPA, than there must be efforts made to keep silver
nanoparticles from being released into the drinking water.
Toxic Substance Control Act
"The Toxic Substances Control Act granted EPA authority to create a regulatory framework to
collect data on chemicals in order to evaluate, assess, mitigate, and control risks that may be
posed by their manufacture, processing, and use. TSCA provides a variety of control methods to
prevent chemicals from posing unreasonable risk.
Under TSCA Section 6, EPA can ban manufacture or distribution in commerce, limit use, require
labeling, or place other restrictions on chemicals that pose unreasonable risks. Among the
chemicals EPA regulates under Section 6 authority are asbestos, chlorofluorocarbons (CFCs),
Page 18 of 21
lead, and polychlorinated biphenyls (PCBs)." ("Toxic substance control," 1976). There is
currently support and legislation that would make silver nanoparticles a chemical that the EPA
would regulate also. This would put silver nanoparticles under the control of the TSCA.
Federal Insecticide Fungicide and Rodenticide Act
"The first pesticide control law was enacted in 1910. This law was primarily aimed at protecting
consumers from ineffective products and deceptive labeling. When the Federal Insecticide,
Fungicide, and Rodenticide Act (FIFRA) was first passed in 1947, it established procedures for
registering pesticides with the U.S. Department of Agriculture and established labeling
provisions. The law was still, however, primarily concerned with the efficacy of pesticides and
did not regulate pesticide use.
FIFRA was essentially rewritten in 1972 when it was amended by the Federal Environmental
Pesticide Control Act (FEPCA). The law has been amended numerous times since 1972,
including some significant amendments in the form of the Food Quality Protection Act (FQPA)
of 1996. In its current form, FIFRA mandates that EPA regulate the use and sale of pesticides to
protect human health and preserve the environment." ("Federal insecticide, fungicide,," 1976).
The U.S. Environmental Protection Agency (USEPA) has gained a large interest in the usage of
silver nanoparticles. USEPA is conducting and funding research to help with understanding the
potential implication of exposure to silver nanoparticles. The agency is currently pursuing
legislation that would place silver nanoparticles under the jurisdiction of the FIFRA. Undj
FIFRA, products containing silver nanoparticles with the aim of killing microbes will be classified
as pesticides. This would allow higher regulations.
Page 19 of 21
Conclusion There are numerous factors to take into account when analyzing silver nanoparticles. The
following conclusions can be made from the information this assessment made.
• Silver nanoparticles have a very strong antibacterial property that is effective at killing
viruses, fungus, and bacteria.
• Silver nanoparticles are a very effective and economical way to get the advantages of
silver.
• Silver nanoparticles can be a very effective tool in the industrial setting due to it's high
conductivity and catalytic properties.
• Silver nanoparticles is found to be toxic to certain aquatic plant life and inhibits growth
• Silver nanoparticles have found to be toxic to certain marine wildlife.
• Silver nanoparticles have been found to have an adverse effect on human health.
• There are not many regulations on labeling and using silver nanoparticles in consumer
<T. il— / V (^ . MV NN^""^
products.
With the information found, it is decided th\ silver nanoparticles will not be used in the
washing machine in questions. VThe pro's, which are the antibacterial and anti-odor properties,
do not outweigh the cons and unknowns, which are the amount of silver nanoparticles being
released into the water and the exposure the users are getting from the use of the machine.
Page 20 of 21
References
Argyria. Wilipedia. com,
Bilber, K. (2011). In vivo toxicity of silver nanoparticles and silver ions in zebrafish (danio rerio). Journal of Toxicology,
' Chen, Z. (2007). A facile and novel way for the synthesis of nearly monodisperse silver nanoparticles. Materials Research Bulletin, 42(9),
Gubbins, E. (2011). Phytotoxicity of silver nanoparticles to lemna minor 1. Environmental Pollution, 159(6),
Main, E. (n.d.). Why "anti-odor" clothes stink Rodale, Retrieved from http://www.rodale.com/silver-nanoparticles
The long history of silver in health and healing, (n.d.). Retrieved from http://www.painreliefwellness.com/clients/2842/documents/History_of_Silver_Usage.pdf
United State Department of Agriculture National Institute of Food and Agriculture, (2003). 21st century nanotechnology research and development act. Retrieved from website: http://www.csrees.usda.gov/nea/technology/in_focus/nanotech_if_resdev.html
U.S. Environmental Protection Agency, (1972). Clean water act (cwa)
U.S. Environmental Protection Agency, (1974). Safe drinking water act (sdwa)
U.S. Environmental Protection Agency, (n.d.). Scientific, technical, research, engineering and modeling support final report state of the science literature review: Everything nanosilver and more.
U.S. Environmental Protection Agency, (1976). Federal insecticide, fungicide, and rodenticide act (fifra)
U.S. Environmental Protection Agency, (1976). Toxic substance control act (tsca)
Yakub, I. (2012). Adhesion of e. coli to silver- or copper-coated porous clay ceramic surfaces . Journal of Applied Physics, 111(12),
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