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Nanosafety assessment methodology. Kaarle Hämeri Professor in Aerosol physics University of Helsinki Finnish Institute for Occupational Health. Take home -message. Aerosol particles have wide range of sizes and other properties

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nanosafety assessment methodology

Nanosafety assessment methodology

Kaarle Hämeri

Professor in Aerosolphysics

University of Helsinki

Finnish Institute for Occupational Health

take home message
Take home -message
  • Aerosol particles have wide range of sizes and other properties
  • Exposure assessment requires determination of relevant aerosol characteristics using right measurement techniques
content
Content
  • Exposure
  • Health effects
  • Aerosol particle properties:
    • Number
    • Size
    • Surface area
  • Case studies
exposure assessment
Exposure assessment
  • Analysis of processes leading to human contact to pollutants after release:
    • inhalation, ingestion, dermal contact
  • Exposure-Event when there is contact with human andenvironment with pollutant for an interval of time
  • Dose-Amount of contaminant absorbed or deposited in thebody
slide5

winter

summer

condensation particle counter cpc
Condensation particle counter (CPC)
  • Single particle is illuminatedwith laser and lightscattering is measured.
  • Beforecounting, particlesaregrownbycondensationprocess

TSI CPC model 3776

TSI CPC model 3007

aerosol particle properties
Particle properties:

Size

Shape (Shape factor χ)

Surface area

porosity

Volume

Mass, density

Chemical compositon

Hydrophobicity, solubility

Surface charge

Electromagnetic properties

Collective properties:

Mass concentration (μg/m3)

Number concentration (1/cm3)

Surface area (m2/m3)

Size distribution (number, surface area, mass)

Aerosol particle properties
different sizes
Different sizes
  • Aerodynamic size
    • Impactor, APS
      • shape, density, size
  • Electrical mobility size
    • Electrostatic classification
      • shape, size
  • Optical size
    • Amount of scattered light
      • refractive index, shape, size
  • Geometric size
    • Microscope
slide10

Size and shape depends on the detection method

and the physical principle used

Kuva:

Mikko Moisio

Dekati Oy

differential mobility analysis

Qsheath + Qexcess

R ≈

Qaerosol + Qclassified

Differential Mobility Analysis

Qaerosol

Qsheath

Qexhaust

E

Qclassified

  • Aerosol particles are charged by gas ions
  • Charged particles migrate across a particle-free
  • sheath flow
  • Particles within a narrow range of mobilities
  • migrate to a sample flow where they are
  • extracted for counting
  • Pecision is determined by flow rates
  • Resolution is approximately
scanning mobility particle sizer smps
scanningmobilityparticlesizer, SMPS
  • Neutraliser, DMA and CPC (+highvoltagesupply and flowcontrols)
slide15

NANO-DMPS

CPC-PAIR

APS

ΔT CPC

IMPACTOR

FMPS

AIS

analogy
Analogy

Particle size classes 1 nm – 100 µm

-> Football hall vs. globe

Or spoonful vs. km3 (1012 l)

Need for investigations of:

-several properties, several intruments and methods...

slide17

Number

Surface area

Volume

nanoparticle surface area monitor
Nanoparticle surface area monitor
  • Detects particles between 10 nm and 1 µm
  • Concentration range 0.01-2500 µm2/cm3
  • 1 s time resolution
  • Counter-flow diffusion charging of particles
  • Detection of the total charge (corresponds to total active surface, condensation sink)
nanoparticles
Nanoparticles

Consepts of nanoparticles (NP) (~1 nm <Dp< 100 nm):

  • Natural NPs, i.e. ultrafine particles (UFP) (from vegetation, sea, volcanoes, …)
  • Incidental NPs (UFP) (combustion, cooking, welding, …)
  • Engineered NPs (NPs, purposely manufactured)

NPsat workplace:

  • Measurementsareneeded for exposureassessment and to controlemissions.
  • NPsareconcidered to bepotentiallymostharmful forhealth.
  • In occupationalenvironmentinhalation is the mostsignificantexposureroute for nanoparticles.
health effects
Health effects
  • Mass?
  • Number?
  • Surface area?
  • Composition?

Importance of the size distribution!

main open questions
Main openquestions:
  • Areengineerednanoparticlesharmful and howharmful?
  • Main sources and emissions?
  • Health relevantproperties and measurables?
    • Whattype of detectors and instrumentsshouldbeused in determiningexposure?
  • Chain: emission-concentration-exposure-dose-effect
lung deposition
Lung deposition

Nanomaterials (CNTs, agglomerates, …)

ENPs

Lung deposition curves defined by International Comission on Radiological Protection

slide31

Suburban, natural ventilation

Suburban, mechanical ventilation

Urban, high mech. ventilation

Urban, low mech. ventilation

slide33

Particle concentration

time series during the

work day

Nanocollection

Nanocoatings

TiO2

CuxOy

MnxOy

MnxOy

particle size distribution time series
Particle size distribution time series

Particlesfromburning of impurities

Nanoparticles

1

Background

particles

Residual

particle

Nucleated

particles

respirator protection factor
Respiratorprotectionfactor

Assignedprotectionfactor (APF)

Level of respiratoryprotectionthatcanbeexpected to beachieved in the workplaceby 95% of adequatelytrained and supervisedwearersusing a properlyfunctioning and correctlyfittedrespiratoryprotectivedevice (Europeanstandard: EN529).

TH2 class:

APF = 20

Schematic of FilterEfficiency vs. ParticleSize

TH3 class:

APF = 200

summary
Summary

Concentrationlevels

  • Discrimination of NPsfrombackgroundparticles is challenging
  • Contribution of NPs to particlenumberconcentrationwas ~99% and to massconcentrationwas < 0.01%

Exposure

  • 70 % of particlesweredeposited in alveolarregionwhere ~99% wasNPs
  • 70 % of masswasdeposited in headairwayswhere <0.01% wasNPs

Recommendations

Massconcentration is notpropermetric in exposureassessment for synthesizedNPs.