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 Exposure assessment requires determination of relevant aerosol characteristics using right measurement techniques

Content Exposure Health effects Aerosol particle properties: –Number –Size –Surface area Case studies

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 and environment with pollutant for an interval of time Dose - Amount of contaminant absorbed or deposited in the body

winter summer

Condensation particle counter (CPC) Single particle is illuminated with laser and light scattering is measured. Before counting, particles are grown by condensation process TSI CPC model 3007 TSI CPC model 3776

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/m 3 ) Number concentration (1/cm 3 ) Surface area (m 2 /m 3 ) Size distribution (number, surface area, mass)

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

Size and shape depends on the detection method and the physical principle used Kuva: Mikko Moisio Dekati Oy

Differential Mobility Analysis E Q aerosol Q sheath Q classified Q exhaust Q sheath + Q excess Q aerosol + Q classified R ≈ 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 Neutraliser, DMA and CPC (+ high voltage supply and flow controls)

ΔT CPC NANO-DMPS CPC-PAIR FMPS AIS APS IMPACTOR

Analogy Particle size classes 1 nm – 100 µm -> Football hall vs. globe Or spoonful vs. km 3 (10 12 l) Need for investigations of: -several properties, several intruments and methods...

Number Surface area Volume

Nanoparticle surface area monitor Detects particles between 10 nm and 1 µm Concentration range µm 2 /cm 3 1 s time resolution Counter-flow diffusion charging of particles Detection of the total charge (corresponds to total active surface, condensation sink)

21 Nanoparticles Consepts of nanoparticles (NP) (~1 nm < D p < 100 nm): Natural NPs, i.e. ultrafine particles (UFP) (from vegetation, sea, volcanoes, …) Incidental NPs (UFP) (combustion, cooking, welding, …) Engineered NPs (NPs, purposely manufactured) NPs at work place: Measurements are needed for exposure assessment and to control emissions. NPs are concidered to be potentially most harmful for health. In occupational environment inhalation is the most significant exposure route for nanoparticles.

Health effects Mass? Number? Surface area? Composition? Importance of the size distribution!

Main open questions: Are engineered nanoparticles harmful and how harmful? Main sources and emissions? Health relevant properties and measurables? –What type of detectors and instruments should be used in determining exposure? Chain: emission-concentration-exposure-dose- effect

24 Lung deposition ENPs Nanomaterials (CNTs, agglomerates, …) Lung deposition curves defined by International Comission on Radiological Protection

Occupational aerosols

Suburban, natural ventilationSuburban, mechanical ventilation Urban, high mech. ventilationUrban, low mech. ventilation

Paint shop

33 Particle concentration time series during the work day TiO 2 Nanocoatings Cu x O y Mn x O y Nanocollection

34 Particle size distribution time series Nanoparticles 1Background particles Particles from burning of impurities Residual particle Nucleated particles

Respirator protection factor TH2 class: APF = 20 Assigned protection factor (APF) Level of respiratory protection that can be expected to be achieved in the work place by 95% of adequately trained and supervised wearers using a properly functioning and correctly fitted respiratory protective device (European standard: EN529). TH3 class: APF = 200 Schematic of Filter Efficiency vs. Particle Size

36 Summary Concentration levels Discrimination of NPs from background particles is challenging Contribution of NPs to particle number concentration was ~99% and to mass concentration was < 0.01% Exposure 70 % of particles were deposited in alveolar region where ~99% was NPs 70 % of mass was deposited in head airways where <0.01% was NPs Recommendations Mass concentration is not proper metric in exposure assessment for synthesized NPs.