Nanotechnology and the Environment - Chapter 11 (end) pot

© 2009 by Taylor & Francis Group, LLC
249
11
Balancing the Risks
and Rewards
Kathleen Sellers
ARCADIS U.S., Inc.
Nanotechnologiesofferbroadpromisetouserawmaterialsandenergymoreef-
ci
ently. Some applications offer medical hope or environmental protection. These
rewards, however, must be balanced against the potential risks from manufacturing,
using, and disposing of products containing nanomaterials. This chapter discusses
toolstoevaluatethebalancebetweenpotentialrisksandrewards,beginningwiththe
conceptofLifeCycleAnalysis(LCA).
11.1 LIFE CYCLE ANALYSIS (LCA)
Life Cycle Analysis (LCA), an integral part of the ISO environmental management
standards(ISO14040),usesamassandenergybalancetodeterminethepotential
effects of product manufacture on human health and the environment. More for-
mally [1],
“LCA is a technique for assessing the environmental aspects and potential impacts
associated with a product by:
Compilinganinventoryofrelevantinputsandoutputsofaproductsystem;
Evaluating the potential environmental impacts associated with those inputs
and outputs;
Interpreting the results of the inventory analysis and impact assessment phases
in relation to the objectives of the study.
•
•
•
CONTENTS
11.1 Life Cycle Analysis (LCA) 249

11.2 Adaptations to Nanotechnology 250
11.2.1 Screeni ng Approach 250
11.2.2 Nano Risk Framework 251
11.2.3 XL Insurance Database Protocol 253
11.3 Summary and Conclusions 257
References 262
© 2009 by Taylor & Francis Group, LLC
250 Nanotechnology and the Environment
LCA studies the environmental aspects and potential impacts throughout the product’s
life (i.e., cradle to grave) from raw materials acquisition through production, use and
disposal. The general categories of environmental issues needing consideration include
resource use, human health, and ecological consequences.”
The formal process of LCA uses very specic information to quantify the con-
sequences of a particular product’s manufacture, use, and disposal. In the develop-
in
g world of nanotechnology, such specic information can be difcult to ascertain.
Many manufacturing processes are still in scale-up; often, and understandably, these
processes are proprietary. Further, as discussed in previous chapters of this book,
relatively little quantitative information is known about the potential releases of
nanomaterials during the use and disposal of products based on nanotechnology,
and the toxicity of those releases if they occur. Relatively few LCAs of nanotechnol
-
og
yhavebeenpublished[2–14].Focusingprimarilyonsafetyandenvironmental
protection, several stakeholders have developed paradigms to evaluate the balance
betweentherisksandbenetsofnanotechnology.
11.2 ADAPTATIONS TO NANOTECHNOLOGY
Threeapproachestoevaluatingnanotechnologyaredescribedbelow:
1. Screening approach developed at a workshop sponsored by The Pew Chari-
table Trusts, the Woodrow Wilson International Center for Scholars/Project

on Emerging Nanotechnologies, and the European Commission [3]
2.TheNanoRiskFrameworkdevelopedbytheEnvironmentalDefense–
DuPont Nano Partnership [4]
3. The XL Insurance Database Protocol, applied to nanotechnology by
researchers at Rice University, Golder Associates, and XL Insurance [8]
The brief summaries that follow illustrate the general mass balance methodolo
-
gies;criticalfeaturesthatcharacterizerisks;andtheuncertaintiesinevaluatingrisks
from newly developed materials for which little information may be available. These
approaches represent two different points of focus: the rst two approaches focus
on the nanomaterials themselves, and the third approach focuses on the processes
used to manufacture the nanomaterials. Either or both of these focal points may
beappropriateforbalancingtherisksandrewardsofaparticularnanotechnology,
depending on the manufacturing process, materials used in that process, quantities
of the nanomaterial used in a commercial product, and the potential for exposure
(includingwhethernanomaterialsarefreeorxed).Ofnecessity,thischaptercannot
present all the nuances of these models, and the reader is encouraged to consult the
cited reference materials for more information.
11.2.1 SCREENING APPROACH
The2006workshop“NanotechnologyandLifeCycleAssessment:ASystems
Approach to Nanotechnology and the Environment” brought together stakehold-
er
s from industry, government, academia, and nongovernmental organizations to
talkaboutthelifecycleanalysisofnanomaterials[3].Recognizingthelimitations
© 2009 by Taylor & Francis Group, LLC
Balancing the Risks and Rewards 251
of applying rigorous LCA to nanotechnology, workshop participants developed an
alternative approach. This ve-step screening process combines elements of LCA,
risk analysis, and scenario analysis:
1.Checkforobviousharm.Considercompliancewithhealth,safety,and

environmental regulations using conventional analyses.
2. Perform a traditional LCA, excluding toxicity impact assessment. Instead,
focus on potential impacts such as global climate change, eutrophication,
etc. If the benets appear to be substantial, then proceed; if not, stop prod
-
u
ct
development.
3. Perform a thorough toxicity and risk assessment (RA) of the product. The
assessment must consider possible exposures in each life-cycle stage.
4.CombinetheresultsofSteps2(LCA)and3(RA)todetermineoverall
impacts.
5.
Perform a scenario analysis to extrapolate the results of Step 4 to large-
scaleusage(e.g.,lookattheimplicationsofusingaverysmallquantityofa
nanomaterial in billions of products).
The authors of this approach acknowledge its current limitations: unavailability
of proprietary information, limited hazard and exposure data, and lack of standard
toolstocombineLCAandRA(Step4).
11.2.2 NANO RISK FRAMEWORK
Environmental Defense, a U.S based non-prot environmental advocacy group, and
the multi-national chemical company DuPont collaborated to develop the Nano Risk
Framework[4].Inthewordsofthedevelopers,
“ThepurposeofthisFrameworkistodeneasystematicanddisciplinedprocessfor
identifying, managing, and reducing potential environmental, health, and safety risks
ofengineerednanomaterialsacrossallstagesofaproduct’s‘lifecycle’—itsfulllife
frominitialsourcingthroughmanufacture,use,disposalorrecycling,andultimatefate.
The Framework offers guidance on the key questions an organization should consider
in developing applications of nanomaterials, and on the information needed to make
sound risk evaluations and risk-management decisions. The Framework allows users

exibility in making such decisions in the presence of knowledge gaps — through
the application of reasonable assumptions and appropriate risk-management practices.
Further, the Framework describes a system for guiding information generation and
updating assumptions, decisions, and practices with new information as it becomes
available.AndtheFrameworkoffersguidanceonhowtocommunicateinformation
anddecisionstokeystakeholders.”
TheFrameworkdiffersfromLCA,asdenedinSection11.1,inthatitfocuseson
potentialenvironmental,health,andsafetyrisks.Itdoesnotconsiderresourceinputs.
The Nano Risk Framework comprises six steps, as described briey below.
Step 1: Describe Material and Application. Th
is step generates an overview of the
physical and chemical properties of the material, sources and manufacturing
© 2009 by Taylor & Francis Group, LLC
252 Nanotechnology and the Environment
processes, and possible uses. The overview includes existing materials that
thenanomaterialmayreplace,andbulkcounterpartsofthenanomaterial.
Step 2: Prole Life Cycle(s). This step includes three components. Each relies
oncompiled“baseset”datatodenethecharacteristicsandhazardsofa
nanomaterial. Where those data are not available, the Framework suggests
using reasonable worst-case default values or assumptions. Analysts can
replacethosedefaultvalueswithactualdataastheybecomeavailable.This
approach will provide an initially conservative estimate of risk that can be
rened if appropriate.
a.
Prole Life Cycle Properties. D
e
velopbasesetdataonphysicaland
chemical properties of the nanomaterial, including property changes
throughoutthefullproductlifecycle.(SeeSection2.3.2.)
b.

Prole Life Cycle Hazards. C
h
aracterize the potential hazards to
human health, the environment, and safety from exposure to this mate-
r
i
althroughoutitslifecycle.Inthisstep,analystscompilefourbasesets
of data: health hazards, environmental hazards, environmental fate, and
safety. Standard methods are not yet available to measure some of these
base set parameters for nanomaterials. Base set data on health hazards
include short-term toxicity, skin sensitization/irritation, skin penetra
-
t
i
on, genetic toxicity tests, and other data. Base set environmental haz-
a
rd
data include acute aquatic toxicology and terrestrial toxicology (i.e.,
earthworms and plants), and may include additional data if needed.
Recommended base set data on the environmental fate of nanomateri
-
a
l
s include physical-chemical properties, adsorption-desorption coef-

c
ients (soil or sludge), and nanomaterial aggregation or disaggregation
in applicable exposure media. They also include data pertaining to per
-
sistence, characterizing biodegradability, photodegradability, hydroly-

s
i
s,andbioaccumulation.Finally,basesetsafetyhazarddatainclude
ammability, explosivity, incompatibility, reactivity, and corrosivity.
c.
Prole Life Cycle Exposure. Q
u
antify the potential for human and environ-
mentalexposuresthroughouttheproductlifecycle.Thisdenitionisdecep-
t
i
velysimple.Theanalystmustconsideropportunitiesfordirectcontactor
release to the environment at multiple stages: manufacture, processing, use,
distribution/storage, and post-use disposal, reuse, or recycling.
Step 3: Evaluate Risks. The
informationcollectedinStep1andStep2iscom-
binedtoestimatetheriskstohumanhealthandtheenvironmentforeach
lifecyclestage.Dependingontheavailabilityofbasesetdata,theinitial
estimates may range from qualitative to quantitative. The analyst must
determinegapsinthelifecycleprolesandeithergeneratedatatollthe
gaps or make reasonable worst-case assumptions.
Step 4: Assess Risk Management. Foreachlifecyclestage,determinethe
actionsneededtoreduceandcontrolrisksfromknownandreasonably
anticipated activities. These actions could include product modica
-
tions, engineering or management controls, protective equipment, or risk
communicationsuchaswarninglabels.Theproductdevelopermighteven
decide to abandon the product.
© 2009 by Taylor & Francis Group, LLC
Balancing the Risks and Rewards 253

Step 5: Decide, Document, and Act. Atthisstage,areviewteamcritically
analyzes the results to decide how to proceed. The team documents and
communicates the results, and determines the course of action for rening
or updating the conclusions.
Step 6: Review and Adapt. This step ensures that the risk characterization
and risk management protocols continue to evolve as new information
becomes available.
TheauthorsoftheFrameworkdevelopedseveralcasestudiestotesttheFrame-
work.Threeofthecasestudiespertainedtomaterialstargetedinthisbook:nano
titanium dioxide, zero-valent iron, and carbon nanotubes. Tables 11.1 through 11.3
summarize those case studies [5–7].
11.2.3 XL INSURANCE DATABASE PROTOCOL
TheprecedingadaptationsofLCAfocusedonthenanomaterialsthemselves.Incon-
trast, researchers at Rice University, Golder Associates, and XL Insurance focused
on the materials and processes used to manufacture nanomaterials [8, 9]. Their risk
analysisusedtheXLInsuranceDatabaseProtocol,whichisusedtocalculateinsur-
ance premiums for the chemical industry, to examine the industrial fabrication of
ve nanomaterials. Those included three of the nanomaterials discussed at length in
this book: single-walled carbon nanotubes, C60 fullerenes, and nano-titanium diox-
ide.Theriskanalysisentailedthefollowingsteps,asshowninFigure11.1.
1. Identify process and materials:
a. Determine synthesis methods, based on process currently used for com-
mercial production or on processes likely to be scaled up for commercial
production.
b. Createblockowdiagramshowinginputstoandoutputsfromtheman-
ufacturing process, omitting energy use.
2. Characterize materials and processes:
a. Collect and characterize data on material properties. Note that these data
pertaintotherawmaterialsusedtomanufacturethenanomaterialsand
thebyproductsoffabrication;theydonotpertaintothenanomaterials

themselves. Critical data include toxicity, as expressed by LC50 and
LD50, water solubility, log K
ow
, ammability, and expected emissions.
Theseinitialdatamaytriggertheneedforadditionalinformation
according to the protocol, so characterization of material properties is
an iterative step. The protocol uses the collected data on material prop-
erties to rank substances by relative risk.
b. Dene manufacturing processes according to characteristics that deter-
mine risks, that is, temperature, pressure, and enthalpy. Then, for each
pointintheprocessandforeachofthesubstancesinvolvedinthe
manufacturing process (except the nanomaterial), identify these char-
acteristics: amount present, role in the process, physical phase at the
temperature and pressure specied; and potential emissions. This step
allowsthemodeltocalculatetheprobabilityofexposurefromanin-
process accident and from normal operations.
© 2009 by Taylor & Francis Group, LLC
254 Nanotechnology and the Environment
TABLE 11.1
Case Study Using the Nano Risk Framework: Titanium Dioxide [7]
Framework Step Analysis
1. Describe Material and
Application
DuPont™ Light S
tabilizer 210 is a surface-treated form of TiO
2
. The product
absorbs and scatters ultraviolet (UV) light; addition of this product to a
polymer protects the material from UV damage when exposed to sunlight.
DuPont™ Light Stabilizer 210 will be transported to plastics producers in

plastic bags, where it will be combined with other ingredients and mixed
with molten polymer; it will comprise <3% of the end product.Potential
applications include outdoor furniture, toys, and sheeting to protect
greenhouses. Use of light stabilizers will extend the product life and
thereby reduce the volume of plastics being landlled.
2. Prole Lifecycle(s)
DuPont™ Light
Stabilizer 210 is a white powder with particle sizes
centered in the range of 130–140 nm. 10–20 wt% falls within the nano
range (i.e., <100 nm). The particles are dense polyhedral TiO
2
crystals
surface treated to control chemical reactions. The particles cannot be
broken down by mechanical action, and their composition will not
substantially change throughout the life cycle.
Toxicity studies showed no signicant difference between the effects of
DuPont™ Light Stabilizer 210 and pigmentary TiO
2
. Toxicity testing
demonstrated low hazard to sh and invertebrates and indicated medium
concern for algae, potentially due to the light-blocking effects.
Titanium occurs naturally in the environment. No established analytical
method can distinguish between the titanium in DuPont™ Light
Stabilizer 210 and naturally occurring titanium.
No accepted protocols for assessing the bioaccumulation potential of
nanomaterials exist.
Worker exposure should be low under normal operating conditions.
Monitoring during production and handling indicated that airborne
concentrations were below the acceptable exposure limit of 2 mg/m
3

.If
exposure limits were exceeded, workers were to don half-mask
respirators with P100 lters.
Exposure is expected to be low throughout the product life cycle because
potential worker exposure is well-managed; due to the low production,
use of engineering controls, and properties of the material, releases to
the environment should be minimal; and the polymer end product should
retain the DuPont™ Light Stabilizer 210 unless incinerated. Emissions
from incineration should be low due to the low concentrations and
emission controls on incinerators.
3. Evaluate Risks Toxicity studies showed no signicant difference between the effects of
DuPont™ Light Stabilizer 210 and pigmentary TiO
2
; both show low hazard.
Further, exposure should be limited. Therefore, “there are no substantive
risk issues associated with manufacture, processing, use or disposal of
DuPont™ Light Stabilizer.”
4. Assess Risk
Management
Based on the conclusions of Step 3, few additional risk management
measures were recommended. Those included personnel scheduling and
monitoring during non-routine activities, and developing recycling
procedures. Some additional toxicity testing was contemplated.
© 2009 by Taylor & Francis Group, LLC
Balancing the Risks and Rewards 255
3. Determine relative risk:
a. Qualitative assessment. In this component of the risk assessment, ana-
ly
stsreviewinformationonthepropertiesofeachmaterialthatcontrib-
ut

etoeitherexposure(basedonemissionestimates)orhazard(based
on properties such as LC50 and LD50), and then rank each material as
low, medium, or high for each of these properties. The aggregate rank
-
in
gprovidesaqualitativeassessmentofrisk.
b. XL Insurance Database Methodology. The protocol estimates risk for
three scenarios based on the manufacturing process, the materials
involved,andtheircharacteristics:
i. Incident risk from accidental exposure resulting from a process
accident.
ii. Normal operations risk from routine emissions during
manufacture.
ii
i.Latentcontaminationfromlong-termoperationsandthesiteof
manufacture.
The
researchers used this protocol to estimate risks from manufacturing several
nanomaterials. Tables 11.4 through 11.6 and Figure 11.2 summarize the analysis of
the risks from manufacturing single-walled nano-titanium dioxide, carbon nano
-
tu
bes, and C60 fullerenes [8, 9].
Forperspective,theresearchteamalsousedtheprotocoltoevaluatetherisks
fromthemanufactureofsixproductsinmorelongstanding,commonuse.Those
productsincludedwine,renedpetroleum,andaspirin.Figure11.2illustratestheXL
Insurance Database scores for selected nanomaterials and these other commercial
products, and indicates which materials in the manufacturing process contributed
most to the estimated risk.
The research team acknowledged that process information may be difcult

toobtain.Theyalsonotedthatmanufacturerswilllikelyreneproductionpro
-
ce
sses, to make them more efcient and perhaps to recycle or reuse some materi-
al
s, as the manufacture of nanomaterials becomes more routine. Nonetheless, this
modelprovidesausefulmeasureoftheindustrialrisksfromthemanufactureof
nanomaterials.
TABLE 11.1(CONTINUED)
Case Study Using the Nano Risk Framework: Titanium Dioxide [7]
Framework Step Analysis
5. Decide, Document,
and Act
The review team accepted the recommendations made in Step 4 and
approved moving forward to product announcement and
commercialization.
6. Review and Adapt
DuPont has scheduled reviews of DuPont™ Light Stabilizer 210 in 2009
and then every 4 years thereafter. “As needed” risk reviews will occur if
triggered by a change in applications, new information on hazard, or
higher than anticipated production.
Summary of Outcome DuPont approved commercial introduction of the product.
© 2009 by Taylor & Francis Group, LLC
256 Nanotechnology and the Environment
TABLE 11.2
Case Study Using the Nano Risk Framework: Nano Zero-Valent Iron [6]
Framework Step Analysis
1. Describe Material and
Application
Nano zero-valent iron in nano-sized particles (nZVI) serves as a reagent to

dechlorinate compounds such as tetrachloroethylene in groundwater.
Vendors ship a highly concentrated slurry of nZVI to a contaminated
site, where it is mixed with water and injected into an aquifer via small-
diameter wells. DuPont did not produce or use nZVI at the time of the
case study.
2. Prole Lifecycle(s) nZVI slurries contain iron particles manufactured by one of several
processes. The properties of the iron particles vary, depending on the
manufacturer. Additives used to stabilize the nZVI slurries also vary
with the manufacturer. Information on both the nZVI particles and the
stabilizers is proprietary. Environmental health and safety data from
suppliers varied in quality and completeness, and may have represented
larger-sized “simple iron powder” rather than nZVI. Toxicological
properties have not been thoroughly investigated. Warnings included the
potential for skin or eye irritation upon contact, irritation of mucous
membranes and upper respiratory tract if inhaled, and may have a
laxative effect if swallowed.
Effective use of nZVI to treat chlorinated compounds in groundwater
requires adequate contact between nZVI and the contaminants;
incomplete destruction could generate toxic partial degradation
products. Spent iron typically precipitates as carbonate or sulde
minerals.
3. Evaluate Risks The case study did not include a risk assessment due to the stage of the
technology and DuPont’s decision not to apply the technology.
4. Assess Risk
Management
The case study did not evaluate risk mitigation measures due to the
stage of the technology and DuPont’s decision not to apply the
technology.
5. Decide, Document,
and Act

“DuPont would not consider using this technology at a DuPont site until
the end products of the reactions following injection, or following a
spill, are determined and adequately assessed.” The case study identied
ve specic questions that must be addressed.
6. Review and Adapt “DuPont will monitor the status of this technology to review and update
the decision as additional information becomes available.”
Summary of Outcome Based on information available as of March 2007, DuPont has no
immediate plans to implement this technology at any DuPont site.
© 2009 by Taylor & Francis Group, LLC
Balancing the Risks and Rewards 257
11.3 SUMMARY AND CONCLUSIONS
Developmentofalternativematerialsandnewcatalystsbasedonnanotechnology
offers many potential benets to human health and the environment. New technolo-
gi
es may save energy, use raw materials more efciently, produce less waste, detect
andtreatenvironmentalpollutants,andofferradicallyeffectiveapproachestodiag-
no
sing and treating disease.
As with any new technological development, these benets may come at some
cost. Chapter 1 described the unintended consequences of some past technological
advancements. LCA offers one tool to anticipate and avoid — or at least control
— the adverse effects of developing nanotechnologies, particularly while regulators
are wrestling with how to apply environmental, worker safety, and consumer protec
-
ti
on regulations to nanotechnologies.
Researchintopotentialrisksisbeginningtoproduceresults.In vitro tests o
fcer-
tainnanomaterialshaveshowneffectsonmammaliancelllines,andsomelaboratory
bioassayshavedemonstratedtoxiceffects.Themostcrucialhazardsmayresultfrom

TABLE 11.3
Case Study Using the Nano Risk Framework: Carbon Nanotubes [5]
Framework Step Analysis
1. Describe Material and
Application
DuPont considered incorporating carbon nanotubes (CNTs) into
engineering thermoplastics to improve mechanical and electrical
properties.
2. Prole Lifecycle(s) Many of the CNT base set data were not available. DuPont purchased
CNTs from outside suppliers in the form of powder (containing 96–
100% CNTs) or encapsulated in polymer pellets (5–50 wt% CNTs).
Absent clear environmental health and safety data, established
exposure limits for CNTs, or toxicity data for the specic CNTs used,
DuPont assumed CNTs were potentially hazardous. Air sample
monitoring occurred during CNT handling and demonstrated the
effectiveness of engineering controls.
Because this was a research and development (R&D) project, the
exposure analysis focused on workers rather than downstream users;
such exposures would be considered if the products were to enter later
stages of development.
3. Evaluate Risks The evaluation did not include a systematic evaluation of risk because of
the development stage.
4. Assess Risk
Management
During R&D, DuPont chose to handle CNTs as hazardous material. Risk
mitigation measures would be rened if nanocomposite products
moved to full production.
5. Decide, Document, and
Act
During R&D, personnel handled small quantities of CNTs in ways that

minimized exposure, utilizing engineering controls, personal protective
equipment, and special operating procedures. Air monitoring
demonstrated the effectiveness of these measures.
6. Review and Adapt The use of CNTs was under continuous review during the R&D process.
Summary of Outcome Research project halted before commercialization for business reasons.
© 2009 by Taylor & Francis Group, LLC
258 Nanotechnology and the Environment
the inhalation of nanoparticulates, which can cause inammation or immune-based
response.Whilesomelaboratoryresultsdogivecauseforconcern,thoseconcerns
mustbeputintocontext.Themethodsofdosingtestorganismsmaynotreectreal-
worldconditions.Measurestakentopreparetestsolutions(forexample,tokeep
nanomaterials in suspension) may introduce other toxicants or otherwise represent
articial conditions. In addition to the hazards presented by the nanomaterials them-
selves, one must consider the hazards posed by other materials used in the manufac-
turingprocessorpartofthenalproduct.SolutionsofnZVI,forexample,maybe
shippedatahighlycausticpH.ManufactureofC60fullerenes,asanotherexample,
requires the use of highly toxic benzene.
Foreitherananomaterialoranassociatedchemicaltocauseariskrequires
acompleteexposurepathway.Thatis,amechanismmustexisttotransferthe
compound or nanomaterial in question from the source in air, water, soil, sediment
to the receptor organism in question. Exposure pathways may be complete during
only portions of a product’s lifecycle — during manufacture, perhaps, or during the
use of a free (not xed) nanoparticle. Little information is currently available on the
end-of-life fate of nanomaterials used in commercial products or the potential for
FIGURE 11.1 SchematicoftheXLinsurancedatabaseandformulationofriskscores[8].
(Reprinted with permission from Relative risk analysis of several manufactured nanomateri-
als: An insurance industry context. Environ. Sci. Technol., 39(October):8985–8994. Copy-
right 2005, American Chemical Society.)
© 2009 by Taylor & Francis Group, LLC
Balancing the Risks and Rewards 259

exposure. The tendency for many nanomaterials to agglomerate or sorb to solids may
limitthatpotential.
Intheend,theeldofnanotechnologyistoobroadandasyettherearetoomany
unknowns for gross generalizations regarding risks and rewards. Some applications
offertrueinnovationandpossiblesolutionstonear-intractableproblems;othernano
promises may be largely marketing hype. Some hazards — specic to particular
materials and exposures — may present signicant risks that warrant careful control
and monitoring. Others may fall within the range that society deems acceptable.
Atthisstageinourunderstandingofnanotechnologyandtheenvironment,Albert
Einsteinmayhaveofferedthebestadvice:“Learnfromyesterday,livefortoday,
hopefortomorrow.Theimportantthingisnottostopquestioning.”
TABLE 11.4
Case Study Using the XL Insurance Database: Nano Titanium Dioxide [8, 9]
Risk Analysis Step Analysis
1. Identify process and materials Hydrolysis and calcinations with chemical
additives to control particle size; process
currently in commercial use
2. Characterize materials
and processes
A. Collect and characterize
data on material
properties
Data compiled for methane, hydrochloric
acid, phosphoric acid, titanium
tetrachloride, carbon dioxide.
B. Dene manufacturing
processes, identify
characteristics that
determine risks
1. Prepare aqueous solution of TiCl

4
in
solution with HCl, HPO
4
.
2. Vacuum-dry solution and spray-dry at
200–250°C to produce dry TiO
2
.
3. Calcinate at 600–900°C for 0.5–8 hours
to produce crystalline nanostructure.
4. Wash precipitate with C
2
H
5
OH, dry, and
mill to nano-sized particles.
3. Determine relative risk A. Qualitative Assessment Materials with very high risk include
phosphoric acid (toxicity), titanium
tetrachloride (toxicity).
B. XL Insurance Database
Methodology
© 2009 by Taylor & Francis Group, LLC
260 Nanotechnology and the Environment
TABLE 11.5
Case Study Using the XL Insurance Database: Single-Walled Carbon
Nanotubes (SWNT) [8, 9]
Risk Analysis Step Analysis
1. Identify process and materials HiPco process of gas-phase chemical-
vapor-deposition; process currently in

commercial use.
2. Characterize materials
and processes
A. Collect and characterize
data on material
properties
Data compiled for carbon monoxide,
sodium hydroxide, iron pentacarbonyl,
carbon dioxide, water.
B. Dene manufacturing
processes, identify
characteristics that
determine risks
1. Introduce Fe(CO)
5
catalyst into injector
ow via pressurized CO.
2. Heat catalyst stream and mix with CO in
graphite heater. Fe(CO)
5
decomposes to
Fe clusters. Standard running conditions
450 psi CO pressure, 1050°C.
3. C atoms coat and dissolve around the Fe
clusters, forming nanotubes. Running
conditions maintained 24–72 hours.
4. Gas ow carries SWNTs and Fe particles
out of the reactor. SWNTs condense on
lters. CO passes through NaOH
absorbtion beds to remove CO

2
and H
2
O,
then recycled.
3. Determine relative
risk
A. Qualitative Assessment No materials present very high risk
according to this model. Materials with
relatively high risk: carbon monoxide
(emissions), iron pentacarbonyl
(emissions) sodium hydroxide (toxicity,
solubility), carbon dioxide (solubility,
emissions).
B. XL Insurance
Database
Methodology
See summary of results in Figure 11.2.
© 2009 by Taylor & Francis Group, LLC
Balancing the Risks and Rewards 261
TABLE 11.6
Case Study Using the XL Insurance Database: Fullerenes [8, 9]
Risk Analysis Step Analysis
1. Identify process and materials Production in laminar benzene-oxygen
argon ame; proprietary process
modied from reference used for mass
production.
2. Characterize
materials and
processes

A. Collect and characterize data
on material properties
Data compiled for benzene, toluene,
argon, nitrogen, oxygen, soot, activated
carbon, carbon dioxide, water.
B. Dene manufacturing
processes, identify
characteristics that determine
risks
1. Laminar ame of C
6
H
6
and O
2
,
diluted with Ar. C:O ratio = 0.760. P
= 12–100 torr. Flame operated 53–170
minutes.
2. Sample of condensable compounds
and soot taken via quartz probe.
3. Sample weighed and extracted with
C
7
H
8
, then ltered and concentrated
by evaporation under N
2
stream.

4. Concentrated solution of C60 and C70
in toluene separated on activated
carbon.
5. C60 ltrate concentrated with rotary
evaporation and drying to 99% pure
product.
3. Determine relative
risk
A. Qualitative Assessment Materials with very high risk include
benzene (toxicity), soot (emissions).
B. XL Insurance
Database
Methodology
See summary of results in Figure 11.2.
© 2009 by Taylor & Francis Group, LLC
262 Nanotechnology and the Environment
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