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VTT Technical Research Centre of Finland

Environmental, health and safety (EHS) aspects of cellulose nanomaterials(CNM)Kangas, Heli

Published: 07/01/2018

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Please cite the original version:Kangas, H. (2018). Environmental, health and safety (EHS) aspects of cellulose nanomaterials (CNM).Biomaterials for Tomorrow, B4T 2018, Kochi, Kerala, India.

Download date: 20. Jun. 2021

https://cris.vtt.fi/en/publications/9200ca3e-b839-49e3-9580-6ee694350a73

VTT TECHNICAL RESEARCH CENTRE OF FINLAND LTD

Environmental, health and safety(EHS) aspects of cellulosenanomaterials (CNM)

Heli KangasBiomaterials for Tomorrow B4TKochi, KeralaJanuary 7-9, 2018

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Motivation

ß Due to their unique nano-specificproperties, cellulose nanomaterials(CNM) have numerous potentialapplications.ß replacement of fossil-based materials

in packaging, deodorizing material inadult diapers, cell growing media…

ß As bio-based materials, CNM are oftenassumed safe.ß However, their nano-specific properties

may potentially make them hazardoustowards humans and the environment.

Source: Stora Enso

Source: Uni-ball

Source: Nippon Paper

Source: Deleon Cosmetics

Source: Natural Friends

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Motivation

ß Biopersistence of long and thin high-aspect ratio fibers is known(case asbestos)ßWood dust is a carcinogenic materialß Nanoscale features give rise to new material properties and

biological behaviorß Decreased particle size – improved penetrationß Increased specific surface area – enhanced interactions with their

biological surroundings

Examples of safetyassessment at VTT

Case 1: Human health - Results on thetoxicity of the smallest fraction of cellulosenanofibrils

Pitkänen, M., Kangas, H., Laitinen, O., Sneck, A., Lahtinen, P., Peresin, M.S. and Niinimäki,J. (2014) Characteristics and safety of nano-scale cellulose fibrils. Cellulose 21, 3871-3886.DOI 10.1007/s10570-014-0397-x

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Background & approach

ß In our previous studies, CNF materials as such showed noindications of toxicity.ß However, with fractionated cellulose nanofibrils, the smallest

fraction showed indications of toxicity/slight toxicity.• Due to cellulose nanofibrils?• Due to the bacteria present in the sample?

¸ Further testing was needed to confirm/disprove the slighttoxicity effects observed¸Finely fibrillated CNF was fractionated into separate size

fractions ensuring that there was no bacterial contamination.

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Fractionation of CNF

1. Finely ground CNF was fractionated using tube flow fractionationinto four fractions

2. The finest material, FR3 and FR4, representing ~20 w-% of theoriginal CNF, were collected

3. Fractions FR3+FR4 were combined and subjected to toxicitytests.

CNF

FR4 FR3 FR1FR2

Original CNF Combined samplefor further tests

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Toxicity testing of the nano-scale fibrils (FR3+FR4)

ß Cytotoxicity in vitroß Highest tolerated dose (HTD)ß Total protein content (TPC)

ß Sublethalityß RNA inhibition test

ßGenotoxicity in vitroß Ames test

ß In vivo testing with nematode modelß Biocide addition before testing (10 mg/l)

Summary – case 1ß Cytotoxicityß No indication of cytotoxic effects in HeLa229 cells were observed in HTD testß Some indication of cytotoxicity with the highest concentration (0.24 mg/ml)

ß Sublethal effectsß No sublethal toxicity in RNA inhibition test

ßGenotoxicityß No indication of genotoxicity

ß Nematode modelß No systemic effects tested in vivo using Nematode

¸FR3+FR4 tested can be considered non-toxic at concentrations lower than0.12 mg/ml¸The material should not be judged toxic based solely on cytotoxicity data,

but should be addressed in relation to other toxicity test results and theintended use of the product.

Case 2: Environmental safety

Vikman, M., Vartiainen, J., Tsitko, I., Korhonen, P. 2015. Biodegradability and Compostability of Nanofibrillar Cellulose-Based Products. J. Polymers Environ Vol. 23 (2015) No: 2, 206-215. doi: 10.1007/s10924-014-0694-3Kangas, H., Pitkänen, M., Vikman, M., Vartiainen, J., Tsitko, I. Cellulose nanofibrils (CNF) and CNF-based products.Biodegradability, Compostability and Safety. 2015 TAPPI International Conference on Nanotechnology for RenewableMaterials, 22-25 June, Atlanta, USA.

Background & Approach

ßThe aim of the work was to obtain more informationon the biodegradability and environmental safety ofCNF and CNF-based products byß Studying the biodegradability of CNF gelsß Studying the biodegradability and compostability of CNF films and

papers containing CNFß Studying the ecotoxicity during biodegradation in the composting

environment.

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Studied materials

ß Cellulose nanofibrils (CNF)ß CNF filmsß Vacuum filtrationß Casting

ß CNF Papersß CNF as an additive in the pulp furnishß CNF in the coating formulation

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Methodology used

ß Biodegradability of CNF gels - OECD 301B ReadyBiodegradability – CO2 evolution (Modified SturmTest)ß Biodegradability of CNF films and papers (in the

composting environment): EN 14046 Packaging.Method by analysis of released carbon dioxide.ß Compostability of CNF films and papers: EN 14045

Packaging. Based on the visual evaluation of thedisintegration.ß Ecotoxicity during disintegration of CNF films and

paper (in the composting environment): ISO 21338standard method (Kinetic luminescent bacteriatest).

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Summary – case 2

ß Fibrillation degree had an effect on biodegradability of CNF samplesß the finer CNF material degraded to a larger extent during the test period.

ß CNF films and papers were biodegradable according to criteria in thestandard and also suitable for composting.ß Papers containing CNF even degraded further than reference paper

during the 65 d test period.ß No acute ecotoxicity was observed during biodegradation of CNF films

and papers.

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Safety testing of cellulose nanofibrils –some lessons learned from cases 2 & 3

ß Selection of right toxicity testing methods crucial!ß Not all suitable for gel-like materials, e.g. restriction of

movementß ECHA’s recommendations

ß E.g. bacterial testing not recommended for nanomaterials

ß Contaminationß False positives

ß Addition of biocidesß need to know the correct dose that does not affect the test

result

Case 3: Risk assessment ofpolymer compositescontaining CNF

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Background and motivation

ß CNF offer sustainable alternative for manufacturing of light-weight composites with reduced carbon footprintß However, little is known about the behavior of CNF at the

different phases of the composites’ life cycleß Exposure to CNFs during production, use or end-of-life may lead

to e.g.ß inflammatory effects of employeesß unwanted adverse effects in the environment

ÿ Risk assessment performed to control and minimize anyunwanted effects

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Approach

Risk = Exposure × Hazard

Identified criticalpoints

1. Occupational2. Environment3. Consumer use4. End-of-life

Information fromthe literature

1. Human health2. Environment

Hazard – information fromthe literature

Reported effects of CNF exposure

To humans

ß Dose-dependent cytotoxicityß Inflammatory effects

ß Potential resolution over timeß Driven by material surface chemistry

ß Biodurability in lungsß Toxicity induced by chemical

modificationß Raw material dependency – fibril

dimensions

To environment

ß Generally not acutely toxic to testorganismsß Surface charge had minimal

influenceß Restriction of movementß Raw material dependency – shapeß Biodegradability dependent on

surface chemistry and fibrillationdegree (available surface area)

Kangas, H., Pitkänen, M. (2016). Environmental, Health & Safety (EHS) aspects of cellulose nanomaterials (CN)and CN-based products. Nord. Pulp Paper Res. J. 31(2), 182-189.

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Critical points in nano-composite manufacturingß The pre-production state, where the nanomaterials are at powder state, is the

one with the highest risk.ß carrying, handling and weighing

ß Critical operations during production are mixing and pouringß Exposure in the post-production stage during demolding, curing and cleaning of

the equipment is also possible, but with lower probability.ß The final nanocomposite is unlikely to present a direct risk because nanoparticles

are trapped into the solid resin.ß However, machining of the composite may lead to exposure – during

manufacturing, cutting and milling of composites containing CNC, the the highestexposure was during cutting of the compositeß For carbon nanotubes (CNT), release was not observed from ductile composite

materials, whereas from brittle materials release was observed.ß Weathering: all the studied materials exposed CNTs to the environment when the

matrix was degraded by UV-light.Soursa et al. Polymeric nanocomposites production risk assessment using different qualitative analyses. Occupational Safety and Hygiene

II - Arezes et al. (eds). Taylor Francis Group, London 2014, pp. 25-30. ISBN-978-1-138-00144-2Geraci C. L., Eastlake, A.C., Dunn, K.L. (2016) Progress in understanding worker exposure and risk for cellulose nanomaterials. Tappi

International Conference on Nanotechnology for Renewable Materials. June 13-16, Grenoble.Schlagenhauf et al. Release of Carbon Nanotubes from Polymer Nanocomposites. Fibers 2014, 2, 108-127; doi:10.3390/fib2020108

Exposure

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Composite production in EU INCOM

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Lab scale production @VTT

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Industrial production @ small scale

ßResin transfer molding – RTMßSeed moulding compound – SCMßVacuum injectionßFilament winding

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Main exposure routes

ß Inhalation exposureß Skin exposure

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1. Potential occupational exposure– critical points

ßSpills during mixing of CNF and polymerßPressure in the mould - RTMßBreakage or leakage of the piping

ßSpills during windingßMachining – cutting, sanding etc.ßHigh probability for exposure according to previous

studiesßMitigation measuresßFume hood, fresh air hood

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2. Potential environmental exposure duringproduction

ßMaterial wasteßRaw materialsßFinishing residues incl. dust

ßWashing waterßContainersßFloors, surfaces etc.

ßMitigationßMinimize raw material wasteßRe-use of finishing residuesßMinimize dust in the working space, fume hoodßSuitable cleaning methods for spills

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3. Consumer use

ß Potential exposure depends on the end use and could take placee.g. byß Wear and tearß Machining, drilling, sanding etc.

ß Case example: sport equipmentß Cutting into size – not probableß Polishing – not neededß Accidental snapping

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4. End of life

ß Depends on the end useß Recyclingß Re-useß Waste disposal: inceniration, landfill

ß In case of sport equipment, inceniration is the most probablerouteß CNFs burned forming carbon

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Conclusions – risk assessment

ßNo major concern found in lab scale or industrialproduction @ small scaleßAs typical for risk assessment, exposure during the

production steps and hazard related to the materialsshould be evaluated case-by-caseß Increasing knowledge of hazardous properties and

behavior of nanomaterials calls for continual review ofthe risk assessment and management measures

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Acknowledgements – case 3

ß The research leading to these results has receivedfunding from the European Union SeventhFramework Programme under grant agreement no608746.ß Co-authors Marja Pitkänen and Lisa Wikström

Risk assessment according to EuropeanCommission Recommendation

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Risk assessment based onß European Commission’s

Guideline on the protectionof the health and safety ofworkers from the potentialrisks related tonanomaterials at work

European Commission. Guidance on the protection of the health and safety of workers from the potentialrisks related to nanomaterials at work. 2014. 63 p.

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A 7-step procedure

1. Identificationß Do nanomaterials exist in the workplace?ß Check the inventories of substances applied and suppliedß Material safety data sheets (MSDS) as primary sources of

informationß Contact the supplier / manufacturer if in douptß REACH, CLP, European Observatory for Nanomaterials

https://euon.echa.europa.eu2. Hazard assessmentß Information about hazardous properties needed: labels, SDS,

occupational exposure limit values and scientific publications.

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A 7-step procedure

3. Exposureß Consider all the routine operations and other foreseeable events in

detailß Some clarifying questions

ß Is the material dusty or the process likely to generate dusts or aerosols?ß Does the process include cutting, shearing, grinding, abrasion, or other

mechanical release?ß How often is exposure likely to occur?

ß Four classes of potential exposure4. Risk categorisation

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A 7-step procedure

5. Detailed risk assessmentß Needed for risk levels 3 & 4ß Quantative assessment of exposure

6. Risk management1) elimination or substitution2) process modification3) isolation or enclosing4) engineering control5) administrative control6) personal protective equipment (PPE)

7. Reviewß Regular check-up

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Recommendations & next steps

ß The safety of cellulose nanomaterials andCNM-based products should be evaluatedcase by caseß Co-operation for the development of testing

methods neededß Validation / standardisation

ß Increased understanding of the knowledgegapsß Short-term / long-term

ß Pro-active communication between academia,producers, authorities etc.ß Data from actual production needed for risk

analysis