ESNano_Environmental impacts of reusable nanoscale silver-coated hospital gowns compared to single-use disposable gowns

EnvironmentalScienceNano

PAPER

Cite this: Environ. Sci.: Nano, 2016,3, 1124

Received 13th June 2016,Accepted 15th August 2016

DOI: 10.1039/c6en00168h

rsc.li/es-nano

Environmental impacts of reusable nanoscalesilver-coated hospital gowns compared to single-use, disposable gowns†

A. L. Hicks,*ab R. B. Reed,cd T. L. Theis,b D. Hanigan,ce H. Huling,c T. Zaikova,f

J. E. Hutchisonfg and J. Millerg

Nanoscale silver has been incorporated into a variety of products where its antimicrobial properties en-

hance their functionality. One particular application is hospital linens, potential vectors of disease transmis-

sion. There is an on-going debate as to whether it is more beneficial to use disposable versus reusable

hospital gowns in efforts to prevent nosocomial infections. This work models the life cycle impacts of

nanoscale silver (nAg)-enabled, reusable hospital gowns from a life cycle assessment perspective and then

compares the midpoint environmental impact data to the use of disposable hospital gowns. A key finding

of this work is the environmental parity (when the environmental impact of nAg and disposable gowns are

equal) of a nAg-enabled gown is 12 wearings. These results suggest that nAg textiles may be key in reduc-

ing the environmental impact of hospitals, while still preventing infection.

1.0 IntroductionThe antimicrobial properties of nanoscale silver (nAg) are ofconsiderable interest from a consumer applicationstandpoint,1–3 resulting in a multitude of nAg-enabled prod-ucts, including wearable textiles, bandages, water filters,toothpaste, air purifiers, baby products, and food storage.4–9

For the purposes of this work, nanoscale will be defined as

materials where one or more of the dimensions are less than100 nanometers (nm). The Woodrow Wilson Center's Projecton Emerging Nanomaterials (PEN)4 database lists 488 nAg-enabled products. The “Health and Fitness” category con-tains the greatest portion of these products, at 266. nAg en-abled textiles are included in this category, suggesting thatthere is the potential for significant adoption of these prod-ucts. The global nAg market is expected to be worth $2415.5million US dollars by 2023.10 North America, in particular,accounted for more than 40% of the global demand for nAgproducts in 2014.

Previous life cycle assessment (LCA) studies have foundthe laundering phase to have the greatest environmental im-pact during the lifetime of a garment,11,12 thus one of thepurported benefits of nAg enabled textiles includes less fre-quent laundering, since antimicrobial effects persist overtime, potentially resulting in a reduction in the overall life-time environmental impact. Meyer et al. used a screening-level LCA to model the inclusion of nAg in socks.13 Walseret al. compared nAg shirts with both conventional (shirtswithout antimicrobial properties) and triclosan (a commonlyused chemical antimicrobial) treated shirts, and found

1124 | Environ. Sci.: Nano, 2016, 3, 1124–1132 This journal is © The Royal Society of Chemistry 2016

aDepartment of Civil and Environmental Engineering, University of Wisconsin-Madison, 2208 Engineering Hall, 1415 Engineering Drive, Madison, WI 53706,USA. E-mail: [email protected] Institute for Environmental Science and Policy, University of Illinois at Chicago,2121 West Taylor, Chicago, IL, 60612, USAc School of Sustainable Engineering and The Built Environment, Arizona StateUniversity, Tempe, AZ, 85287, USAdDepartment of Chemistry and Geochemistry, Colorado School of Mines, Golden,CO, 80401, USAeDepartment of Civil and Environmental Engineering, University of Nevada, Reno,NV, 89557, USAf Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR,97402, USAgDune Sciences, Inc., 1900 Millrace Drive, Eugene, OR, 97403, USA† Electronic supplementary information (ESI) available. See DOI: 10.1039/c6en00168h

Nano impact

Nanoscale silver is the most common nanomaterial incorporated into consumer products, due to its antimicrobial nature. This antimicrobial benefit isrelevant with respect to textiles in medical settings, where there is a current debate as to the use of disposable versus reusable linens for diseasetransmission prevention. In this study a life cycle assessment of a commercial nanosilver treatment is compared in the context of a hospital setting for usein reusable gowns compared to disposable gowns. This study is valuable with respect to understanding the potential environmental advantages of theapplication of nanosilver in a healthcare setting.

Environ. Sci.: Nano, 2016, 3, 1124–1132 | 1125This journal is © The Royal Society of Chemistry 2016

consumer actions during the use phase greatly influence theresults.14 Hicks et al.15 found that the portion of the life cycleof the textile with the greatest impact depends largely on theinitial silver content, laundering behavior, and environmentalimpact category considered. Additionally, Pourzahedi andEckelman conducted a LCA study of nAg bandages, findingthat the quantity of bulk silver used was the greatest contrib-utor in terms of environmental impact to the process of nAgsynthesis (and thus not the reagents or heatingemployed).5,16 The present work seeks to expand on previousstudies by investigating the environmental impacts of a newnAg synthesis method, and a process to attach the nAg to tex-tile surfaces. The textiles produced by this method are evalu-ated, in comparison to disposable textiles, for their potentialto reduce disease transmission and environmental impact inthe health care field.

Although the majority of the nAg is commonly lost from afabric after relatively few launderings, there is the potentialfor reapplication to the garment.15 Most nAg-enabled textilesare sold with the silver already in place, with no potential toreplenish the lost silver.17,18 However, a nAg aftermarket solu-tion (the nAg studied in this work), can be attached to textilesusing a commercial washer, the nAg solution, and a proprie-tary linking agent. This application (and the possibility forreapplication) would be particularly beneficial in a hospitalor long-term care facility setting, where there is the potentialfor textiles to serve as vectors of pathogen transmission. Thisis especially true for textiles that are not frequently launderedsuch as curtains.

Hospital acquired infections are the 4th leading cause ofdeath in the United States (behind heart disease, cancer, andstroke).19 Reducing transmission of infection and/or transferof contamination is imperative, and has clear applicability inhospital and other sterile settings. In a hospital setting thesources of potential contamination are numerous, and in-clude the floor, bed linens, gowns, overbed tables, and bloodpressure cuffs.20 Methicillin-resistant Staphylococcus aureus(MRSA) infections have been reported by the Centers for Dis-ease Control (CDC), to spread through indirect contact, suchas touching contaminated objects (including sheets, towels,wound dressings, and clothing) that have come into directcontact with the infected wound.21 In one study, hospitallinens were evaluated for their role in microbial transfer,clean linen (prior to patient contact), dirty linen, and staffuniforms were all found to be contaminated with pathogenicmicrobes.22 With hospital acquired infections in adults cost-ing approximately $10 billion in the United States annually,biocidal textiles (such as nAg-enabled) have been proposed asan effective method for the reduction of hospital acquiredinfections.23–25

Currently, there is significant debate as to whether dis-posable or multiuse products are a better choice in medicalsettings, such as hospitals with respect to diseasetransmission.26–28 Previous LCA work by Overcash29 andPonder30 has identified the potential to significantly reducethe environmental impact of hospital gowns by switching

to reusables. This case study is useful to illustrate the po-tential benefits, under a well-defined usage scenario, ofnAg-enabled textiles when compared to their disposablecounterparts to inform the debate. Eighty percent of hospi-tals in the United States employ single use (disposable)hospital gowns and drapes.31,32 One surgical waste auditfound that 39% of the surgical waste was due to disposablesurgical linens, amounting to 10.2 kg per surgery.33 Approx-imately 80% of hospitals in the United States utilize dispos-able drapes and gowns.33 In the United States, in 2010,there were 51.4 million in patient surgical procedures,34

suggesting a potential to produce 419.2 million kg of surgi-cal waste due to disposable linens annually for only inpa-tient surgical procedures. The use of reusable gowns anddrapes would significantly reduce that quantity of waste.One concern in this debate is whether or not the multiuseproducts will serve as reservoirs for pathogens, with the po-tential to contribute to nosocomial infections.22 Biocidaltextiles, including nAg-enabled products, have the potentialto reduce the bacterial load stored in textiles, while poten-tially reducing the environmental impact by moving to re-usable products,30 in the hospital setting. Also, some hospi-tals have transitioned to allowing medical staff to launderitems such as scrubs and uniforms at home.35 This raisesthe possibility of introducing these pathogens into thehome environment, and the potential for ineffective laun-dering due to home laundering equipment, although so farthat has not been shown to occur.35 This work will explorethe relative life cycle impacts of disposable versus multiusenAg-enabled hospital gowns produced using the nAg prod-uct and attachment process developed by Dune Sciences.Dune Sciences manufactures nanoscale products, such asnAg coatings, and grids for different microscopy samplepreparations (such as functionalized grids for transmissionelectron microscopy).36

A consequence of the adoption and use of nAg enabledproducts is the introduction of nAg to the environment. Asstated previously there is significant variation in the quantityof silver attached and thus lost during the lifetime of nAg tex-tiles.15 Recent work by Gilbertson et al.37 characterized themany challenges of deriving factors to characterize the toxic-ity of nanomaterials (with nAg particularly discussed). Basedon sets of meta-analysis they concluded that for nAg when afixed percentage of ionic release is assumed (as is done inthis work) that there is the potential to overestimate the tox-icity impacts of the nAg.37 The speciation of the silver enter-ing the wastewater treatment plant is relevant from a toxicityperspective. Although the presence of ionic silver in the en-vironment due to release from nAg enabled textiles, repre-sents a potentially negative impact to the environment,38,39

most studies have concluded that the silver will be in theform of Ag2S,

40–42 although secondary forms such as AgCl(ref. 43) are also possible. In freshwater conditions, the antic-ipated discharge location, Ag2S has not been found to be bio-available, and due to this is not considered to be as toxic asionic silver.44

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The impact of the silver discharged to the environment isalso a function of scale. Broad scale adoption of these nAgtextiles would introduce more silver into the environment,and thus potentially amplifying its impact on the environ-ment. nAg particles in the wastewater treatment system havebeen found to inhibit nitrification at a concentration of 0.1mg L−1.40,45,46 Nitrification is the process of converting am-monia to nitrite and nitrate in the wastewater system. Anaer-obic digestion is a method for handling the biosolids pro-duced in the wastewater treatment system, and producesbiogas during the digestion or composting process. A signifi-cant difference in biogas production as a function of silverconcentration in the biosolids has not been observed with re-spect to anaerobic digestion or composting,41,42,47 however areduction in landfill gas production has been observed as afunction of high silver levels.47 The nAg whose life cycle im-pact is presented in this work has been characterized by Reedet al.48 with respect to antimicrobial tests, zebra fish toxicity,and utilizing electron microscopy.

At the same time there is an environmental impact of notsilver enabling the hospital gowns, and instead continuing touse disposable gowns or utilizing a different biocidal agent.Approximately 80% of surgical sheets and gowns utilized inthe United States are disposable.31,32 As previously men-tioned, this contributes to the generation of surgical waste.Walser et al.14 compared different methods of antimicrobiallyenabling non-hospital textiles utilizing both silver and theantimicrobial Triclosan. They found the environmental im-pact of Triclosan application to be similar to that of a con-ventional textile, while the environmental impact of utilizingthe nAg was largely dependent on the synthesis process, butcould be similar to that of a conventional textile. Beyond theenvironmental impact of waste generation, a disposable gownhas an embodied energy of 3.01 MJ, while a reusable gownhas about 9 times that amount (27.3 MJ).30 If a lifetime of agown is considered to be 75 wearings,30 then the potentialfor significant environmental savings from a raw materialsand manufacturing perspective is evident.

2.0 Methods2.1 Goals

The potential environmental benefit of the nAg modelled inthis work is further evaluated by applying it to a case study ofhospital gowns. Hospital gowns present a potential applica-tion for use of nAg for its antimicrobial properties, as hospi-tal textiles have been identified as potential vectors of thetransmission of hospital acquired infections.26 This is largelydue to the issue that some pathogens have been found to re-main on and in textiles even after laundering.49–55 Biocidalfinishes on textiles, along with the use of disposable textilesare two methods that could be used to combat this, each witha different environmental impact. In this work, reusable pa-tient hospital gowns coated with the nAg product will becompared with the use of disposable gowns from an environ-mental impact perspective. Although this case study focuses

on a specific, well-defined usage scenario, the approachshould also be useful to evaluate the potential benefits ofnAg enabled textiles under other use scenarios.

2.2 Nanoparticle synthesis and attachment

The nAg is synthesized starting from silver nitrate, the mostcommon starting point for nAg synthesis.56 It is synthesizedaccording to a proprietary methodology utilized by Dune Sci-ences, with a 60% yield.57 Due to a non-disclosure agree-ment, the exact synthesis process may not be described inthis work. However, aggregate information may be found inthe supplemental material for this article hosted online. ThenAg is then attached to the polyester fabric with a proprietarytethering method. The tethering process uses various chemi-cal reagents along with heat and water in an industrial laun-dering application, resulting in a concentration range of 20–25 micrograms (μg) of nAg/gram (g) of textile. An electricitymix relevant to the United States was utilized in that analysis.

2.3 Hospital gown assumptions

The values used for the raw materials, manufacturing, andlaundering of the hospital cotton–polyester blend gown wereobtained from Ponder,30 who utilized the environmental im-pact category of cumulative energy demand (CED) in heranalysis.30 The reusable gown has a mass of 230 g, and an as-sumed lifetime of 75 launderings. The concentration of nAginitially applied to the reusable gown was taken to be 20 μgg−1. The raw materials and manufacturing data for the dis-posable hospital gown was also obtained from Ponder.30 Adisposable gown is considered to be single use and have amass of 60 g, and is disposed of after a single wearing.

The data utilized for modeling the cumulative energy de-mand (CED) impact category of hospital gowns were takenlargely from literature. Ponder30 found the impact of the rawmaterials and manufacturing of a reusable gown to be 27.31mega joules (MJ) per gown, and 3.01 per disposable gown.The impact per gown per laundering was determined by Pon-der30 to be 0.51 MJ, with the most significant contributionsdue to washing, rinsing, and neutralizing (0.34 MJ), extrac-tion (3.08 × 10−3 MJ), and drying (3.66 × 10−2 MJ). The dis-posal data, in this instance modeled as landfill disposal, wasmodeled utilizing the Sima Pro software, and a mass basedapproach. The impact of synthesizing the nAg was completedutilizing the LCA inventory data whose impacts are presentedin section 3.1, and applying the CED impact category.

2.4 Laundering procedure

Understanding the rate of silver loss from the textile is criti-cal, as the nAg bestows the antimicrobial benefits on the tex-tile. The nAg-enabled textiles studied in this work were foundto maintain their antimicrobial efficacy even after losses ofsilver during, down to a concentration of 2 μg g−1.48 In theirliterature review, Hicks et al.15 found silver loss from fabricsduring laundering varies considerably. In order to obtain sil-ver loss data on the particular nAg and attachment method

Environmental Science: NanoPaper


studied in this work, laundering experiments wereperformed, as are detailed below.

The nAg-enabled textile (in this case entirely polyester)samples were subjected to consecutive washings as a meansof assessing potential silver losses to the environment. Thetextile samples were split into two groups: those washed innanopure water, and those washed in detergent. A standardAmerican Association of Textile Colorists and Chemists(AATCC, 2003 formulation) laundry detergent was used inhalf the wash samples to mimic conditions used for washingin the home, as it was anticipated that the use of laundry de-tergent would have the potential to influence the quantity ofsilver lost during the laundering process. The concentrationof detergent was equivalent to 40 microliters (μL) concen-trated detergent in 50 milliliters (mL) of nanopure water.Triplicate fabric swatches (∼2 g each) were cut from eachshirt and placed in 250 mL polypropylene bottles with 50 mLof water (with or without detergent) and 5 glass beads for agi-tation. The bottles and beads were washed in 10% nitric acidfor at least 24 hours and rinsed at least three times withnanopure water between textile washing experiments. Thebottles containing fabric swatches were secured in an end-over-end mixer and rotated at 40 revolutions per minute(rpm) for 30 minutes to provide agitation during washing.The fabrics were removed from the bottles, and excess waterwas allowed to drip from the fabrics before the fabrics weretransferred to aluminum foil drying dishes. The textiles werethen transferred to a drying oven and dried overnight at 50°C, a temperature similar to household dryers. This was doneto remove any excess water from the fabric which mightcause extended release and dissolution of Ag particles on thefibers over time. The tweezers were rinsed with nanopure wa-ter between uses. For selected samples, aliquots of wash wa-ter were taken after washing the textiles but before acidifica-tion for ICP-MS analysis. These aliquots were filtered using a30 kDa centrifugal ultrafilter for 30 minutes at 5000 g. Theremaining wash solutions were acidified to 2% HNO3 in the250 mL bottles and analyzed by ICP-MS (Thermo X-Series II,Waltham, MA).

2.5 Silver losses

The silver released during the laundering is assumed to entera wastewater treatment plant, and undergo standard treat-ment conditions, where 95% will be removed into the bio-mass.40 The silver contained in the biosolids is expected tobe in the form of Ag2S and AgCl, two relatively stable formsof silver in the environment.40,42,43,47 The 5% of silverdischarged from the WWTP is modeled in the form of silverions (Ag+) released to freshwater. Ionic silver is considered tobe more toxic in the aquatic environment, than its more sta-ble counterparts.38,39,44 The toxicity of the Ag+ released fromthe textile during laundering is characterized using the dis-charge of Ag+ to freshwater systems allocation in SimaPro(version 8.1). In this allocation, Ag+ loss contributes to thenon-carcinogenic and ecotoxicity impact categories, at a rate

of 2.45 × 10−3 CTUh and 1.34 × 106 CTUe per kilogram ofionic silver discharged respectively.

2.6 End of life

Textiles in the United States are typically disposed of in a mu-nicipal solid waste setting, which includes landfilling or in-cineration.58,59 Based on the allocation of waste in otherhealthcare studies, the disposal of the textiles will bemodeled in a landfill setting.60,61

2.7 Scope

Fig. 1 presents the overall scope of the LCA performed in thiswork. This work analyzes the lifecycle impact of the synthesisof nAg, its application to textiles in a hospital setting (initialapplication and reapplication), and laundering of the textile.An analysis of the use of disposable hospital gowns is alsopresented for comparison. A major consideration in the cur-rent healthcare debate with respect to reusable and dispos-able textiles in a healthcare setting is the control of nosoco-mial infections through the reduction of textiles as a vectorof pathogen transmission, as posited by Ponder.30

Two levels of scope are analyzed in this study. The firstlevel, nAg synthesis, which is denoted by the red box inFig. 2, analyzes the impact of synthesizing the nAg andattaching it to the textile surface. These impacts are com-pared to those of other nAg synthesis methods found in liter-ature. The second level of scope, applying the nAg to the lifecycle of a hospital gown, is denoted by the blue. Where thenAg synthesized previously is applied (and reapplied) to a re-usable hospital gown, and the environmental impact is com-pared to using disposable hospital gowns. This work addi-tionally includes the environmental impact of the quantity ofsilver lost along with the eventual end of life disposal of thehospital gowns.

Fig. 1 The scope of LCA in this study, level 1 (within the red box)represents the nAg synthesis, level 2 (within the blue box) representsthe large scale impacts of the hospital gown application. Italicizedinputs and outputs are included in the analysis.



2.8 LCA methodology

Sima Pro (version 8.1)62 was used to model the life cycle ofthe nAg synthesis and attachment, with inventory valuesobtained from both laboratory experimental data and theEcoinvent database (version 2.2). Mid-point environmentalimpacts were evaluated using the U.S. Environmental Protec-tion Agency's Tool for the Reduction and Assessment ofChemicals and Other Environmental Impacts (TRACI).63 Nineimpact categories were evaluated in addition to cumulativeenergy demand. The nAg synthesis and attachment data werethen put into context, exploring the environmental impact ofthe use of nAg on hospital gowns. Multiple functional unitsare employed to fully describe the system. The first func-tional unit is per 4600 μg of nAg, the amount added to a hos-pital gown and at each application. The second functionalunit is per one wear and laundering (where applicable) in or-

der to compared the reusable nAg enabled gown with the sin-gle use gown, over a lifetime of 75 wearings.

3.0 Results and discussionThe LCA results presented are heavily informed by experi-mental work, and thus in each portion of the life cycle the ex-perimental work (if applicable) will be presented first, withthe life cycle modeling work presented second.

3.1 Silver synthesis results

The environmental impact of synthesizing the nAg particlesis presented in Fig. 2a. The source of the silver (in this casesilver nitrate) is the most significant contributor to the im-pact of nAg synthesis, similar to the findings of Pourzahediand Eckelman.5 The attachment of the nAg to the textile (aspresented in Fig. 2b) includes the use of reagents, water, andenergy (at the laboratory scale). The reagent and energy usagehave the greatest environmental impacts. In all of the envi-ronmental impact categories considered, the impact isgreater to attach the nAg to the textile than it is to synthesizeit. It should be noted, however, that these impacts are for alaboratory scale attachment, and later in the work only the re-agents necessary for attachment will be considered, as the at-tachment will performed as part of a routine commerciallaundering procedure.

Comparing the process for nAg synthesis used by DuneSciences to those evaluated by Pourzahedi and Eckelman al-lows for conclusions as to the relative environmental impactto be drawn.16 These results are presented in Table 1.

In Table 1 the methods with the greatest and least envi-ronmental impact in each impact category are highlighted,using red and green respectively. The Dune nAg process hadthe greatest environmental impact in three categories (acidifi-cation, non carcinogenics, and respiratory effects), while FSPdominated the remaining of the impact categories. Overall,the RMS-AR-N method had the most number of “least” envi-ronmental impacts. This suggests that the synthesis utilizedin this work is similar from an environmental impact stand-point to that of other commonly used methods.

One important caveat in interpreting the data in Table 1 isthat the functional unit is strictly based upon the mass ofnAg. In fact, the nanoparticle size, size distribution, purityand coating chemistries are all different for each synthesisand the performance of the different nAg forms depend uponthose variables. Thus, direct comparisons of impacts wouldrequire more detailed assessment of the performance of eachform of nAg as a textile coating. Nonetheless, it does providea baseline at which to compare impacts with respect to or-ders of magnitude differences.

3.2 Potential silver losses to the environment

Fig. 3 presents results from nAg fabric laundering experi-ments as cumulative silver washed from the fabric as a func-tion of number of laundering cycles completed, as described

Fig. 2 Midpoint LCA results of portions of the lifecycle a) nAgsynthesis, b) attachment (per 1 hospital gown containing 4600 μg ofnAg).‡

‡ The units employed in each category are as follows: ozone depletion (kg CFC-11 eq.), global warming (kg CO2 eq.), smog (kg O3 eq.), acidification (mol H+

eq.), eutrophication (kg N eq.), carcinogenics (CTUh), non carcinogenics (CTUh),respiratory effects (kg PM10 eq.), and ecotoxicity (CTUe), with total valuesdisplayed at the top of the chart for each category, per 4600 μg of nAg.



in the methods of laundering. In part A (Fig. 3), the silverloss is presented for laundering in both DI water and with de-tergent. Less silver is lost by the textile when it is launderedutilizing the detergent. Part B presents the results of launder-

ing the textile until the majority of the silver was lost in DIwater, with the majority of the silver lost by the 11th launder-ing cycle. The error bars on each figure are used to illustratevariation among the laundering experiment results whichwere done in triplicate. The results of Fig. 3 suggest that thesilver lost may be approximated using the first order rate law,assuming an initial silver concentration on each textile of 20μg g−1. This gives a rate constant for the textile laundered indetergent of 0.235 with time being defined as per laundering.This would result in a concentration of silver below 2 μgg−1,48 the effective antimicrobial limit of the textile after the17th laundering.

3.3 Environmental impact of hospital gowns

Ponder investigated the life cycle implications of both dispos-able and reusable patient hospital gowns, utilizing a func-tional unit of 75 000 gown wearings, composed of 1000 reus-able gowns each laundered 74 times, or 75 000 disposablegowns.30 The study found the lifetime energy consumptionfor their functional unit for the reusable gown to be 65 049mega joules (MJ) and 225, 947 MJ for the disposable gown.These data suggest that using reusable gowns would result inan energy savings of about 71% compared to the disposablegowns. Given the observed loss of nAg in Fig. 3, the silvercould be reapplied at each set of 17 launderings. Fig. 4 pre-sents a comparison of the environmental impact of using anAg-enabled gown (with reapplication of the nAg solutionand linking agent every 17 launderings) to the disposablegown, utilizing energy consumption (cumulative energy de-mand) as the impact category, for the sake of comparability,as that was the sole impact category utilized by Ponder. Froman impact perspective, it is more energy intensive to attachthe nAg (2.73 MJ) than to synthesize the nAg itself (5.27 ×

Table 1 Environmental impact of nAg synthesis by route for 4600 μg of nAga

a The abbreviations for the types of nAg synthesis are defined as CR-EG (silver nitrate and ethylene glycol), CR-SB (silver nitrate and sodiumborohydride), CR-TSC (silver nitrate and trisodium citrate), CR-STARCH (silver nitrate and potato starch), FSP (silver and flame spray pyrolysis),RMS-AR-N (silver and reactive magnetron sputtering with argon and nitrogen gas), and AP (silver and arc plasma). More detail in regards to thenAg synthesis using each method may be found in ref. 14. Per 4600 μg of nAg.

Fig. 3 Cumulative silver losses as a function of textile laundering a)laundered DI water and detergent, b) laundered with DI water for anextended number of launderings.



10−2 MJ), per textile per application. However, the attachmentis designed to be performed in an industrial laundering set-ting, meaning that the silver and linking solution could beadded to every 17th laundering of the hospital gowns (at anenergy cost of 1.94 MJ per reapplication per gown – includingthe nAg solution). Eqn (1) and (2) express the energy con-sumption of each gown option as a function of number oftimes that the gown has been worn.

DispImp = (3.01 MJ + 7.89 × 10−4 MJ) × (wear) (1)

ReuseImp = (27.3 MJ + 1.94 MJ) + (0.51 MJ × wear) (2)

The impact of the disposable gown (DispImp) is a func-tion of the number of equivalent wearings, meaning that anew gown (3.01 MJ) is used for each wearing. The impact ofthe reusable gown (ReuseImp) is a function of the raw mate-rials and manufacturing used to create the gown (27.31 MJ),and 1.94 MJ is the initial silver synthesis and attachment andthe amount of energy used to launder the gown (0.51 MJ),with the assumption that the gown is laundered prior to itsfirst wear in order to attach the silver. Additionally, at every17th laundering 1.94 MJ will be added to the impact to ac-count for the nAg applied during the laundering cycle. Theend of life disposal of the two hospital gown options will oc-cur in a landfill setting, and will contribute to each dispos-able gown (7.89 × 10−4 MJ) and once to the reusable gown af-ter 75 wearings (1.16 × 10−2 MJ). These impacts are per gown,and are based on the mass of each gown going to thelandfill.

Initially, using the disposable gown reduces the amountof energy consumed in the system. However, at wear 12, thereusable gown becomes the less energy intensive option. As-suming a gown lifetime of 75 wears,30 this suggests that thereusable gown may be a better choice from an energy con-sumption standpoint. Although the impact of the reusablegown appears to be linear over time, small stepwise increasesare seen every 17 launderings due to the reapplication of thenAg. Also, the silver loss is non-linear over time, however,that uncertainty is not incorporated into Fig. 4, as the nAgemitted in ionic form to freshwater does not contribute to

the CED. The nAg modeled in this work has been tested withrespect to antimicrobial efficacy, and has been found to pro-vide inhibition at concentrations as low as 2 μg Ag g−1

fabric.48

3.4 Uncertainty and sensitivity

As with most LCA work, uncertainty exists within this work.In order to quantify the potential influence of the inputs andassumptions utilized on the impacts quantified, scenariosare posited such as changes in yield of the nAg produced, re-agent, water, and energy consumption. In each instance,presented in Fig. 5, the initial value utilized in the analysishas been increased and decreased by 50%.

The sensitivity of the impacts to a 50% change in the in-ventory is presented in Fig. 5, a percentage change of eachimpact category. The inventory item with the most influenceis the amount of silver utilized to produce the nAg. This sug-gests that increasing the yield of the process would notice-ably decrease the corresponding environmental impact ofsynthesizing the nAg. The smallest percentage of change wasseen for the water and electricity consumption categories,suggesting that the environmental impacts are least sensitiv-ity to these inputs.

Uncertainty exists with respect as to the acceptable silverconcentration remaining on the textile for the healthcare fa-cility. How often the nAg is reapplied will shift the environ-mental impact of the reusable gown, and thus how manylaunderings it would take for the reusable gown to be less en-ergy intensive than its disposable counterpart. Fig. 6 presentsthese points of parity with respect to frequency of nAgapplication.

The frequency of the nAg reapplication to the reusablegown influences the lifetime environmental impact of thegown, and thus when parity with the disposable option willbe achieved. When the nAg is reapplied to the gown duringevery laundering cycle, it will require 28 wears for the reus-able gown to have a lower environmental impact than thedisposable gown. Although this is more than double the

Fig. 5 Sensitivity of impacts to inventory inputs (OZ – ozone depletion,GW – global warming, SM – smog, AC – acidification, EU – eutrophication,CN – carcinogenics, NC – non carcinogenics, RE – respiratory effects, EC –eco toxicity). Percent change of impacts if expressed in decimal format.

Fig. 4 Lifetime energy consumption for reusable vs. disposablehospital gowns with nAg.



number of wears required for parity at the rate of applicationof every 17 wears, parity is still possible within the functionallifetime of the gown. At a reapplication frequency of both 5and 10 wearings, parity would be at 13 launderings, which isnot very different from the 12 launderings achieved withreapplication after every 17 wearings. And finally, withreapplication every 15 or 20 wearings, parity with the dispos-able gowns would remain at 12 wearings. This uncertaintyanalysis suggests that although more frequency applicationof the nAg to the textiles would require more resources andthus have a greater environmental impact, that there is stillpotential within the 75 wearings lifetime of the reusablegown for the reusable gown to have a lesser environmentalimpact than the disposable option.

3.5 Limitations

This work explores the environmental impact of a method forsynthesizing and attaching nAg which may be completed in acommercial laundering setting. This process is explored withrespect to hospital textiles, and gowns in particular, as a casestudy where an antimicrobial textile would be potentially ben-eficial, and nAg reapplication could occur. This study haslimitations, however, in particular only one synthesis and at-tachment process for nAg was analyzed. Also, the environ-mental impact of excess silver during synthesis and the silverlost to the biosolids is not explored in this work. Additionally,the comparison of reusable and disposable gowns relies onprior work by Ponder,30 and utilizes only a single impactcategory.

4.0 ConclusionsA commercially available synthesis and attachment processfor nAg-enabled textiles was evaluated utilizing a midpointLCA. Using nine impact categories, the environmental impactof the synthesis for the nAg produced by this method wasfound to be similar to that of other nAg synthesis processes.The nAg was bound to the textiles using a chemicalcrosslinking agent. Although the attached nAg was nearly alllost from the textile by the 17th laundering, a novel aspect ofthis nAg process is that it may be reapplied in an industrial

laundering setting. The application of such a process was in-vestigated in the context of patient hospital gowns, a knownvector for disease transmission. Previous work has shownthis nAg system to provide microbial inhibition, even at fairlylow concentrations.49 When the nAg enabled textile was com-pared to disposable hospital gowns, the energy consumptionwas found to be much less during the lifetime of the reusablehospital gown than continuously using disposable garments.This suggests that nAg-enabling of reusable hospital gownsmay be a method for simultaneously lowering the environ-mental impact and maintaining the antimicrobial perfor-mance needed to combat textile vector pathogen transmis-sion. The type of analysis used in this study should proveuseful in evaluating the potential for a net environmentalbenefit for nano-enabled consumer products over a variety ofusage scenarios.

AcknowledgementsThe authors acknowledge the generous support of the U.S. Envi-ronmental Protection Agency Assistance Agreement No.RD83558001-0 that funded this research. This work has notbeen formally reviewed by EPA. The views expressed in this doc-ument are solely those of the authors and do not necessarily re-flect those of the Agency. EPA does not endorse any products orcommercial services mentioned in this publication.

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ESNano_Environmental impacts of reusable nanoscale silver-coated hospital gowns compared to single-use disposable gowns