Measurements of Particle Emissions from Nanotechnology Processes, with Assessment of Measuring Techniques and Workplace Controls

Publication Date : 2012
Code : 125
261 Visited Entry Date : 2017/10/04

AUSTRALIA

English
Volume 140 Pages
Document type Report
Subject Characterization & Testing ; Occupational Safety
Summary

The overall aim of this project was to contribute to existing knowledge regarding methods for measuring characteristics of airborne nanoparticles and controlling occupational exposure to airborne nanoparticles, and to gather data on nanoparticle emission and transport in various workplaces.

The scope of this study involved investigating the characteristics and behaviour of particles arising from the operation of six nanotechnology processes, subdivided into nine processes for measurement purposes. It did not include the toxicological evaluation of the aerosol and therefore, no direct conclusion was made regarding the health effects of exposure to these particles.

This research included real-time measurement of sub, and supermicrometre particle number and mass concentration, count median diameter, and alveolar deposited surface area using condensation particle counters, an optical particle counter, DustTrak photometer, scanning mobility particle sizer, and nanoparticle surface area monitor, respectively. Off-line particle analysis included scanning and transmission electron microscopy, energy-dispersive x-ray spectrometry, and thermal optical analysis of elemental carbon. Sources of fibrous and non-fibrous particles were included.

Objectives of project were to:

1. Identify and review scientific literature regarding methods and methodology pertinent to the characterisation of airborne engineered nanoparticles

2. Identify and quantify particle emission sources in workplaces that manufacture or handle engineered nanoparticles, e.g. fibrous nanomaterials, nanoparticles that are carcinogenic, mutagenic, asthmagenic, or reproductive toxins (CMAR), insoluble nanomaterials, and soluble nanomaterials (subject to availability)

3. Characterise the emitted particles in terms of airborne concentration, size, and morphology at the emission point (temporal study)

4. Pilot a study of spatial particle characteristics so as to gain insight into the transport and fate of particles, and

5. Identify, quantify and propose measures for the mitigation of the potential exposure relative to the task.
Content

1 Executive Summary

   Scope and limitations of this study

   Summary of main findings

      Particle exposure and emission

      Advice on particle assessment

      Triggers for particle control strategies

 

Abbreviations

 

Glossary

 

2 Introduction

 

3 Overall Aim

 

4 Objectives

 

5 Scientific Literature Regarding Common Methods and Instrumentation Pertinent to the Characterisation of Airborne Engineered Nanoparticles

   5.1 Properties of nanoparticles that influence measurement decisions

      5.1.1 Particle size

      5.1.2 The surface area and the reactivity of that surface area

      5.1.3 Particle number

      5.1.4 Solubility and biopersistence

      5.1.5 Shape and fibres

      5.1.6 Primary particle size, aggregation, and agglomeration

   5.2 Measurement of nanoparticles

      5.2.1 Metrics, methods, and instruments

      5.2.2 Summary of some of the currently available instruments and methods for characterising particle emission and transport

         5.2.2.1 Personal samplers for time resolved nanoparticle measurements

      5.2.3 Response of instruments to aerosols dominated by specific particle characteristics

      5.2.4 Sampling and measurement strategy issues

      5.2.5 Conclusions from review of literature

 

6 Research Methodology

   6.1 General Information

   6.2 Instrumentation

   6.3 Experimental design

   6.4 Analyses

      6.4.1 Transmission Electron Microscope, Scanning Electron Microscope and Energy-dispersive X-ray spectrometry

      6.4.2 Thermal optical analysis of elemental carbon

      6.4.3 Processing and Analysis of Data

 

7 Qualifying the Significance of the Results of Particle Measurement

   7.1 Particle control values

      7.1.1 Australian Workplace Exposure Standards

      7.1.2 Recommended Exposure Limits

      7.1.3 Proposed workplace exposure limits

      7.1.4 Benchmark Exposure Level

      7.1.5 Local Particle Reference Value

   7.2 Criteria for assessing excursion above the particle control values

   7.3 Factors that should be considered when comparing and interpreting particle measurement data

 

8 Results of the Characterisation of Particle Emission, Transport, Morphology, and Chemical Composition for Six Engineered Nanoparticle Aerosols

   8.1 Mean particle metrics for all six nanomaterial aerosols

   8.2 Process One – grinding and extrusion of modified TiO2

      8.2.1 Experimental Design and Conditions

      8.2.2 Results

         8.2.2.1 Time series of particle number and mass concentration, count median diameter, and alveolar deposited surface area

         8.2.2.2 Electron microscope

         8.2.2.3 Discussion

   8.3 Process Two – manufacture of clay-polyurethane nanocomposite material

      8.3.1 Experimental Design and Conditions

      8.3.2 Results

         8.3.2.1 Time series of particle number and mass concentration, count median diameter, and alveolar deposited surface area

         8.3.2.2 Influence of local extraction ventilation upon the particle concentration within the work area

            8.3.2.2.1 Description of the local extraction ventilation servicing the extruder machine

         8.3.2.3 Electron microscopy analysis of particles

         8.3.2.4 Discussion

   8.4 Process Three – grinding of titanium dioxide powder

      8.4.1 Experimental Design and Conditions

      8.4.2 Results

         8.4.2.1 Time series of particle number and mass concentration, count median diameter, and alveolar deposited surface area

         8.4.2.2 Discussion

   8.5 Process Four – jet milling of modified clay particles

      8.5.1 Experimental Design and Conditions

      8.5.2 Results

         8.5.2.1 Time series of particle number and mass concentration

         8.5.2.2 Influence of local mechanical dilution ventilation upon the particle concentration within the work area

         8.5.2.3 Discussion

   8.6 Process Five – Decanting of single and multi-walled carbon nanotubes

      8.6.1 Experimental Design and Conditions

      8.6.2 Results

         8.6.2.1 Time series of particle number and mass concentration, count median diameter, and alveolar deposited surface area

         8.6.2.2 Electron microscopy analysis of particles

            8.6.2.2.1 Methodology

            8.6.2.2.2 Results

         8.6.2.3 Estimating mass concentration of carbon nanotube aerosols - elemental carbon analysis and real time mass concentration measurements

         8.6.2.4 Discussion

   8.7 Process 6 – Synthesis of carbon nanotubes using Chemical Vapour Deposition

      8.7.1 Experimental Design and Conditions

      8.7.2 Results

         8.7.2.1 Time series of particle number and mass concentration

         8.7.2.2  Influence of process enclosure and fume cabinet upon the particle concentration within the work area

         8.7.2.3 Discussion

 

9 Comparison and Evaluation of the Response of Different Instrumentation and Measurement Methodology to a Range of Airborne Engineered Particles

   9.1 Methodology

   9.2 Discussion

 

10 Discussion of, and Recommendations for, Characterisation and Reporting of Temporal and Spatial Concentrations of Airborne Engineered Nanoparticles

   10.1 Recommendation 1: Utilise Particle Control Values when evaluating particle emission and exposure

      10.1.1 Hierarchy of Particle Control Values for nanomaterials

   10.2 Recommendation 2: Minimise the number of particle metrics to be characterised

   10.3 Recommendation 3: Utilise real-time particle number and mass concentration data to identify sources of particle emission, spatial variation, and to validate effectiveness of engineering controls in containing particle emissions

   10.4 Recommendation 4: comprehensively characterise background and incidental particle number and mass concentration

   10.5 Recommendation 5 – utilise excursion guidance criteria relative to particle background to evaluate significance of temporal and spatial particle variation

      10.5.1 Application of excursion guidance criteria to research data contained in this report

      10.5.2 Examination of findings in relation to background particle reference values

      10.5.3 Approach summary

   10.6 Recommendation 6: Utilise a three-tiered particle evaluation process

      10.6.1 Tier One - comprehensive survey of the process environment

         10.6.1.1 Qualitative survey

         10.6.1.2 Quantitative survey

      10.6.2 Tier Two – comprehensive characterisation of real-time particle number and mass concentration

         10.6.2.1 Characterisation of particle source emission

         10.6.2.2 Estimation of exposure

         10.6.2.3 Validation of effectiveness of particle emission controls

         10.6.2.4 Summarising overall findings of Tier Two assessment

      10.6.3 Tier Three - utilise sampling methods for off-line analysis of particle morphology, chemical composition, and mass concentration, and real-time SMPS

         10.6.3.1 Collection of particles at emission point

         10.6.3.2 Collection of particles in the breathing zone of workers

         10.6.3.3 Case study of tier three assessment

   10.7 Recommendation 7: calculate impact of instrument accuracy on measurement results

   10.8 Recommendation 8: calibrate equipment

   10.9 Recommendation 9: utilise same equipment for on-going measurement of same process

   10.10 Recommendation 10: record and report the relative humidity and temperature of the work area

   10.11 Recommendation 11: A minimum data set should be included in all reports of assessment of nanomaterial aerosol

 

11 References

 

12 Appendix A

 

13 Appendix B – Pearson’s Correlation Results

   13.1 Grinding of titanium dioxide powder

   13.2 Extrusion of titanium dioxide and polyethylene materials

   13.3 Extrusion of clay platelets and polyurethane materials

   13.4 Grinding of titanium dioxide powder

   13.5 Jet milling of clay platelets

   13.6 Decanting of single-walled carbon nanotube powder

   13.7 Decanting of multi-walled carbon nanotube powder

 

14 Appendix C
Organization
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