identity, grouping and characterisation of silver based biocidal
TRANSCRIPT
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Identity, grouping and Identity, grouping and
characterisation of silver based characterisation of silver based
biocidal active substances biocidal active substances
including nanoincluding nano--silversilver
Ulrike Frank
Swedish Chemical Agency
February 2012
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Identity, grouping and Identity, grouping and
characterisation of silver based characterisation of silver based
biocidal active substances biocidal active substances
including nanoincluding nano--silversilver
• What are biocides?
• The evaluation of silver under the biocides legislation
• Applications of biocidal silver
• Treated articles and their implications for risk assessment
• When is nano an issue?
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What are Biocides?What are Biocides?
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What are Biocides?What are Biocides?
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What are Biocides?What are Biocides?
• Biocides are agents usually meant to kill organisms
• They must not be sold without pre-marketing approval = authorization.
• Details are regulated in the European Biocides Directive (98/8/EC) respectively in the Biocides Regulation (Reg. EC No xxxx/2012) � to be published in summer 2012
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The evaluation of silverThe evaluation of silver
• Silver is a potent antimicrobial agent
• Silver is used as active substance in biocidal
products and in treated articles
• All active substances have to be authorized to be permitted to be placed on the market after
May 2014
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The evaluation of silverThe evaluation of silver
• KemI (SE) is responsible for the evaluation of
silver as an active substance within BPD
• At the moment: transitional period = unregulated
market
• In future: only silver uses which show acceptable
risks get authorized
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Silver?Silver?
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Silver?Silver?Silver containing substance (SCAS)
CAS
No.
Elemental silver
a) Particulate silver 7440-22-4
b) Silver ionisation systems
7440-22-4
Silver adsorbed to silica dioxide Not yet allocated
Silver chloride adsorbed to titan dioxide Not yet allocated
Silver nitrate 7761-88-8
Silver sodium hydrogen zirconium phosphate 265647-11-8
Silver zinc zeolite 130328-20-0
Silver copper zeolite 130328-19-7
Silver phosphate glass 308069-39-8
Silver borosilicate glass 308062-97-7
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Example: Silver (zinc) zeoliteExample: Silver (zinc) zeolite
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Example: NanoExample: Nano--silver compositesilver composite
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Example: Silver nitrateExample: Silver nitrate
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NanoNano--Silver: DefinitionSilver: Definition
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Biocides Regulation (from COM recommendation)Art. 3, (z) "nanomaterial" means a natural or manufactured active substance or
non-active substance containing particles, in an unbound state or as an
aggregate or as an agglomerate and where, for 50 % or more of the particles in
the number size distribution, one or more external dimensions is in the size
range 1 nm-100 nm; …
For the purposes of the definition of nanomaterial, ‘particle’, ‘agglomerate’ and
‘aggregate’ are defined as follows:
(a) ‘particle’ means a minute piece of matter with defined physical boundaries;
(b) ‘agglomerate’ means a collection of weakly bound particles or aggregates
where the resulting external surface area is similar to the sum of the surface
areas of the individual components;
(c) ‘aggregate’ means a particle comprising of strongly bound or fused
particles;
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NanoNano--Silver: DefinitionSilver: Definition
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“Nano definition is lawyers' paradise, says expert
A member of the UK government's Advisory Committee on Hazardous Substances (ACHS) has described the EU definition of nanomaterials adopted last October as a "lawyers' paradise" that will be difficult for regulators to work with. …”
(Source: ENDS, 14th december 2011)
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Nano?Nano?Silver containing substance (SCAS)
CAS
No.
Elemental silver
a) Particulate silver 7440-22-4
b) Silver ionisation systems
7440-22-4
Silver adsorbed to silica dioxide Not yet allocated
Silver chloride adsorbed to titan dioxide Not yet allocated
Silver nitrate 7761-88-8
Silver sodium hydrogen zirconium phosphate 265647-11-8
Silver zinc zeolite 130328-20-0
Silver copper zeolite 130328-19-7
Silver phosphate glass 308069-39-8
Silver borosilicate glass 308062-97-7
www.kemi.se
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Nano?Nano?Silver containing substance (SCAS)
CAS
No.
Elemental silver
a) Particulate silver 7440-22-4
b) Silver ionisation systems
7440-22-4
Silver adsorbed to silica dioxide Not yet allocated
Silver chloride adsorbed to titan dioxide Not yet allocated
Silver nitrate 7761-88-8
Silver sodium hydrogen zirconium phosphate 265647-11-8
Silver zinc zeolite 130328-20-0
Silver copper zeolite 130328-19-7
Silver phosphate glass 308069-39-8
Silver borosilicate glass 308062-97-7
www.kemi.se
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Nano?Nano?Silver containing substance (SCAS)
CAS
No.
Elemental silver
a) Particulate silver 7440-22-4
b) Silver ionisation systems
7440-22-4
Silver adsorbed to silica dioxide Not yet allocated
Silver chloride adsorbed to titan dioxide Not yet allocated
Silver nitrate 7761-88-8
Silver sodium hydrogen zirconium phosphate 265647-11-8
Silver zinc zeolite 130328-20-0
Silver copper zeolite 130328-19-7
Silver phosphate glass 308069-39-8
Silver borosilicate glass 308062-97-7
www.kemi.se
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Silver as antimicrobial agentSilver as antimicrobial agent
Diffu
sio
n
aktiv
Ag+
SH
-P
O4
3-
Silver salts
Silver zirconium phosphat
Silver zeolite Silver glass Silver –chloride-nitrate
Silver Silver on SiO2; Silver chloride on
TiO2
Elementary
silver
Silver
composites
Ag+ Ag+ Ag+ Ag+ Ag+ Ag+
Ag+
Ag+
Ag+
Ag+
Ag+
Antimicro-bial effect
caused by Ag+
Silver ion exchangers
Notified active substan-ces
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Silver as antimicrobial agentSilver as antimicrobial agent
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Silver sulfide
Ag+ release in deionized waterlow high
Silver hydrogen zirconium phosphate
Silver zeolite
Silver chloride compos
ite
Elemen-tal silver (mikro)
Silver glass
Silver nitrate
Nano-Silver composite?
Ag+ release varies over a wide range, dependent
on: - Silver releasing agent
- pH and ion-content of solvent
Nano-silver possibly has a higher release rate
per mass of silver due to bigger surface area
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Does size matter?Does size matter?
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Example water solubility:
Silver powder Nano silver in compound
Particle size 2-55 µm 5-20 nm
Water solubility 22.8 mg Ag/L 210.3 mg Ag/L
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Does size matter?Does size matter?
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Silver electrode Powdered silver
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Biocidal applicationsw
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http://www.zeomic.co.jp/english
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Biocidal applicationsBiocidal applications
• Infinite application(possibilitie)s:http://www.alibaba.com/showroom/germ-free-material_3.html
http://www.housekeepingchannel.com/tag_238_Antimicrobialhttp://www.zoflora.co.uk/
• Silver:The Silver Nanotechnology Commercial Inventory,Emma Fauss, University of Virginia, September 2008; http://www.nanotechproject.org/process/assets/files/6718/fauss_final.pdf
• products on the market contain real nano-silver, or are named ”nano” because that is catchy
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Applications with antimicrobial Applications with antimicrobial
SilverSilverExample: Toilet seatExample: Toilet seat
Plastic or Coating Bulk Silver Particle
+
Ag+
++ +
+++
++
+
+
+
+
++
Water film
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Applications with antimicrobial Applications with antimicrobial
SilverSilverExample: Toilet seatExample: Toilet seat
Plastic or Coating Nano Silver Particle
+ Ag+
++
+++
++
+
+
+
+
++
Water film
+ +++ +
+
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Applications with antimicrobial Applications with antimicrobial
SilverSilverExample: Toilet seatExample: Toilet seat
Plastic or Coating Nano Silver Particle
+ Ag+
++
+++
++
+
+
+
+
++
Water film
+ +++ +
+
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Applications with antimicrobial Applications with antimicrobial
SilverSilverExample: Toilet seatExample: Toilet seat
Plastic or Coating Nano Silver Particle
+ Ag+
++
+++
++
+
+
+
+
++
Water film
+ +++ +
+
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How is antimicrobial silver applied?
Most variably!
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Active substanceMasterbatch Treated articleCoating
Fiber
Silver
additive
Fiber
Silver
additive
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Quantity of silver applicationsQuantity of silver applications
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Silver applications treated article
coating textile liquid consumer
liquid industrial
Overall distribution (%)
31 49 10 3 7
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Exposure Assessmentw
ww
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Exposure Assessment
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New in Biocides RegulationNew in Biocides Regulation
Article 4, Conditions for approval
…….
4. The approval of an active substance shall not cover
nanomaterials except where explicitly mentioned.
This is a result of EP’s position during first reading:
“….Special attention to nanomaterials
Lastly, with doubts remaining over the possible long-term health effects of nanomaterials, MEPs insisted on the need for separate assessment of such particles in biocidal products” (source: EPs website)
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New in Biocides RegulationNew in Biocides Regulation
• Treated articles are defined (Art. 3 (l))
• Use of a biocidal product includes use in treated articles (Art. 3 (k))
• Articles may only be placed on the market in Europe when treated with biocidal products which contain active substances authorized in Europe
• Treated articles have to be labelled:
- if they make a biocidal claim
- if they contain nanomaterial
- if there is considerable release (decided upon at active substance
authorization)
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ConclusionsConclusions
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• Nano is an issue – amongst others – for the evaluation of silver
• The original active may be in nano-size � the form man and environment are exposed to might be very different
• The focus on ”Nano” can obscure the issues which deserve even more attention
• Exposure for different uses and application areas is the biggest challenge in the evaluation of silver
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ConclusionsConclusions
Nano or not nano. Is that a question?
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Yes
Yes
Yes
Yes
No No
No
No
No
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Applications with antimicrobial Applications with antimicrobial
SilverSilver
Spray applications:
Probably high exposure during use
� Different assessment depending on (end-)use??
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?
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Kemis Washing Study
Scope: 30 different textiles were purchased and analysed for silver before, after 3 x and after 10 x washing
•The original content varied to a large extent. Between 0,4- 1360
mg/kg textile
•In general the original content of silver was between 10-50 mg/kg
•After 10 washes the samples had leached between 10-98 %. In
many cases > 80 %
•Already after 3 washes 10 of the samples leached > 43 %
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Different Assessment of Different Different Assessment of Different
Silver Forms?Silver Forms?Silver form Competent
Authority Report
Inclusion decision
Silver zinc zeolite x x
Silver copper zeolite x x
Silver nitrate x x
Silver sodium hydrogen zirconium phosphate
x x
Silver phosphate glass x x
Silver borosilicate glass x x
Silver (electrode,
powder)
x x
x
Silver chloride on TiO2 x x
Silver nano-composite x x
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Risk Assessment
Risk: Hazard x Exposure
• Hazard:
inherent properties of a substance
�Tox studies with representative organisms
• Exposure: For every compartment and life stage
�Model calculations
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Chemical
properties
Exposure > Effect = Risk
Risk characterisation – compartment, life stage
Exposure Effect
Risk Assessment
For every compartment/
life stage
For every
compartmentExposure < Effect =
acceptable Risk!