Topic 3: Metrology and dose metrics for hazard and exposure assessment throughout the life cycle. Günter Oberdörster University of Rochester, NY

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1 Topic 3: Metrology and dose metrics for hazard and exposure assessment throughout the life cycle Günter Oberdörster University of Rochester, NY

2 Concepts to be addressed: Key parameters of nanomaterials affecting hazard properties as basis for testing and for using metrics Mode of action and choice of dosemetrics Approach involving dosimetry and dosemetrics for regulatory hazard and risk characterization

3 Hazard All NPs are toxic Nanotoxicology - Hype Cycle Realistic Assessment of Hazard and Risk Increasing Insight of Nanotoxicity Concepts Appreciation of Reality Effects and Biokinetics of UFP (1990s) Time

4 Conceptual Depiction of Factors for Considering Dose-dependent Transitions in Determinants of Toxicity From: Slikker Jr., et al. 2004

6 Nano TiO 2 repeated bolus instillation into mouse: 7.5 mg into mouse = 17.5 grams into human nose!

7 17.5 g TiO 2 (P25)

8 DPPC/Alb-Dispersed MITSUI Multiwalled Carbon Nanotubes (MWCNTs)

9 Bolus Dosing of MWCNT: Granulomat. Inflam. and Mesothelioma = Asbestos like? Induction of mesothelioma in p53+/- mouse by intraperitoneal application of multi-wall carbon nanotube Takagi et al., J. Toxicol. Sci. 33 (No. 1): , 2008 Carbon nanotubes introduced into the abdominal cavity of mice show asbestos-like pathogenicity in a pilot study Poland et al., Nature Nanotechnology 3, , 2008 Induction of mesothelioma by a single intrascrotal administration of multi-wall carbon nanotube in intact male Fischer 344 rats Sakamoto et al, J.Tox. Sci., 34, 65-76, 2009 Dose-dependent mesothelioma induction by intraperitoneal administration of multiwall carbon nanotubes in p53 heterozygous mice Takagi et al, Cancer Sci., 103(8), , 2012 Length-dependent pleural inflammation and parietal pleural responses after deposition of carbon nanotubes in the pulmonary airspaces of mice Murphy et al, Nanotoxicology 7(6), 2013

10 Physico-chemical NP Properties Affecting Hazard Potential Size (aerodynamic, hydrodynamic) Size distribution Shape Agglomeration/aggregation Density (material, bulk) Surface properties: - area (porosity) - charge - reactivity - chemistry (coatings, contaminants) - defects Solubility/Sol-Rate (lipid, aqueous, in vivo) Crystallinity Biol. contaminants (e.g. endotoxin) Properties can change -with: method of production preparation process storage (aging) -when introduced into physiol. media, organism -throughout life-cycle (from cradle to grave)

11 Physico-chemical NP Properties Affecting Hazard Potential Size (aerodynamic, hydrodynamic) Size distribution Shape Agglomeration/aggregation Density (material, bulk) Surface properties: - area (porosity) - charge - reactivity - chemistry (coatings, contaminants) - defects Solubility/Sol-Rate (lipid, aqueous, in vivo) Crystallinity Biol. contaminants (e.g. endotoxin) Properties can change -with: method of production preparation process storage (aging) -when introduced into physiol. media, organism -throughout life-cycle (from cradle to grave) Key parameter: Dose! Expression of Dose?

12 MIP-2, pg/ml MIP-2, pg/ml Sayes et al., 2007: ASSESSING TOXICITY OF FINE AND NANOPARTICLES (In vitro and In vivo) Crystalline Silica; Amorphous Silica; Nano Zinc Oxide; Fine Zinc Oxide Rat Alveolar Macrophage Culture Control Control Concentration (µg/cm ) Amorphous SiO 2 Crystalline SiO 2 Conclusion: comparison of in vivo and in vitro results demonstrated little correlation

13 In vivo inflammation # PMN x In Vivo/In Vitro Correlation, Highest Measured Responses (Sayes et al, 2007) 8 NZO CS 6 AS 4 FZO 2 R 2 =0.12 P=0.66 Crystalline Silica Nano Zinc Oxide Amorphous Silica Fine Zinc Oxide MIP-2 (pg/ml) In vitro macrophages Rushton et al. 2010

14 In vivo inflammation # PMN x In Vivo/In Vitro Correlation, Highest Measured Responses (Sayes et al, 2007) 8 NZO CS 6 AS 4 FZO 2 R 2 =0.12 P=0.66 Crystalline Silica Nano Zinc Oxide Amorphous Silica Fine Zinc Oxide MIP-2 (pg/ml) In vitro macrophages Rushton et al. 2010

15 Response (Y) Dose-Response Analysis: Steepest slope (max response/dose) as indicator of toxicity y n y i +1 Steepest slope = y x i + 1 i y x i i y i x i x i +1 x n Dose (X) Rushton et al. 2010

16 In vivo inflammation In Vivo/In Vitro Correlation, Highest Responses Per NP Surface Area (Sayes et al, 2007) PMN Number x 10 5 /cm NZO Crystalline Silica Nano Zinc Oxide FZO Amorphous Silica Fine Zinc Oxide R 2 =0.92 P=0.04 CS AS MIP-2 x10 5 (pg/ml)/cm 2 In vitro macrophages Rushton et al. 2010

17 Physical Dose-Metrics for NPs that Correlate with Biol./Toxicol. Effects (Mode of Action): Mass Number Surface Area (as surrogate for surface props.) Volume correlation between these should be part of NP characterization

18 Retention T1/2 Particle Volume Morrow Hypothesis (1988): Lung particle overload associated impairment of alveolar macrophage clearance function correlates with phagocytized particle volume. Qu ic k Tim e and a TI FF (Unc om pres s ed ) d ec o m pres s or are needed to see this picture. inflammation, fibrosis, tumors In chronic rat studies with PSP % Relative phagocytized particle volume (% of AM volume)

19 Retention T1/2 Particle Volume Morrow Hypothesis (1988): Lung particle overload associated impairment of alveolar macrophage clearance function correlates with phagocytized particle volume. But: Only for Poorly Soluble Particles of low cytotoxicity (PSP) Qu ic k Tim e and a TI FF (Unc om pres s ed ) d ec o m pres s or are needed to see this picture. inflammation, fibrosis, tumors In chronic rat studies with PSP % Relative phagocytized particle volume (% of AM volume)

20 Lung Particle Overload, Nanoparticles and AM mediated Particle Clearance: Does volumetric overload concept apply to nanoparticles? 12-Week Inhalation Exposure, Ultrafine and Fine TiO 2 and Cristobalite (SiO 2 ) Retained dose/10 6 AM at end of exposure Mass Volume Surface Number Test Particle Retention µg nl % of AM volume cm 2 x 10-9 control = 1 Control TiO 2 fine * (250 nm) TiO 2 ultrafine * (25 nm) Cristobalite ~ * *Significantly different from control Oberdörster et al, 1994

21 Lung Particle Overload, Nanoparticles and AM mediated Particle Clearance: Does volumetric overload concept apply to nanoparticles? 12-Week Inhalation Exposure, Ultrafine and Fine TiO 2 and Cristobalite (SiO 2 ) Retained dose/10 6 AM at end of exposure Mass Volume Surface Number Test Particle Retention µg nl % of AM volume cm 2 x 10-9 control = 1 Control TiO 2 fine * (250 nm) (578) (58) TiO 2 ultrafine * (25 nm) (768) (77) Cristobalite ~ * (24) (2.4) *Significantly different from control (packing density volume) Oberdörster et al, 1994

22 Correlation between surface area of TiO 2 particles phagocytized by AM and pulmonary retention half-time of inhaled polystyrene test particles From: Oberdörster et al., 1994 (EHP)

23 Surface Reactivity as Dose-Metric, e.g., ROS inducing potential to determine response per unit particle surface area DCFH-DA (2-7 dichlorofluorescin-diacetate) assay FRAS (ferric reducing ability of serum) assay Vit C assay others as screening tool for categorization of NPs based on reactivity in using cell-free assay, but only for Hazard Identification [Bello et al., 2009; Rushton et al., 2010]

24 Cell-free ROS (DCFH oxidation) Response vs In Vivo Rat PMN (Intratracheal Instill) Response to Nanoparticles Normalized to Particle Surface Area In vivo inflammation TiO2-D TiO2-F TiO2-M PS-NH3 Carbon Ag-35 Cu-40 Au-50 PMN Number/cm R = 0.86 P = ROS/cm 2 In vitro Cell- free ROS Rushton et al. 2010

25 Cell-free ROS (DCFH oxidation) Response vs In Vivo Rat PMN (Intratracheal Instill) Response to Nanoparticles Normalized to Particle Surface Area PMN Number/cm 2 In vivo inflammation TiO2-D TiO2-F TiO2-M PS-NH3 Carbon Ag-35 Cu-40 Au For Hazard screening! 10 4 R = 0.86 P = ROS/cm 2 In vitro Cell- free ROS Rushton et al. 2010

26 Risk = f (hazard; exposure) Risk Risk: High Extreme Very high Moderate Low Very low Minimal Hazard Exposure

27 Risk = f (hazard; exposure) MWCNT? Risk Risk: High Extreme Very high Moderate Low Very low Minimal Hazard tightly embedded NM Exposure

28 Risk = f (hazard; exposure) MWCNT? Risk Risk: High Extreme Very high Moderate Low Very low Minimal Hazard Comparison to Benchmarks! tightly embedded NM Exposure

29 Approach for Comparative Hazard and Risk Characterization of Inhaled Nano-Particles Based on Subchronic (3 months) Rat Inhalation Studies Positive Benchmark Nanomaterial to be tested Negative Benchmark Desirable: Quantitative Toxicity Endpoints; Retained Lung Burdens Exposure Dose Response Dosemetrics: mass; surface area; volume; number slope analysis Comparative Hazard Ranking by appropriate Dosemetrics NOAEL; BMD Comparative Risk Characterization (rat) Subchronic safe Exposure Level dosimetry validation in vitro-in vivo comparison In vitro: acellular, Cellular, ATS Human Equivalent Concentration (HEC) Uncertainty Factors Occupational Exposure Level OEL inter-species dosim. extrapol. intra-species dosimetric extrapolation to chronic exposure Chronic Exposure Level (rat)

30 Approach for Comparative Hazard and Risk Characterization of Inhaled Nano-Particles Based on Subchronic (3 months) Rat Inhalation Studies Positive Benchmark Nanomaterial to be tested Negative Benchmark Desirable: Quantitative Toxicity Endpoints; Retained Lung Burdens Exposure Dose Response Dosemetrics: mass; surface area; volume; number slope analysis Comparative Hazard Ranking by appropriate Dosemetrics NOAEL; BMD Comparative Risk Characterization (rat) Subchronic safe Exposure Level dosimetry validation in vitro-in vivo comparison In vitro: acellular, Cellular, ATS Human Equivalent Concentration (HEC) Uncertainty Factors Occupational Exposure Level (OEL) inter-species dosim. extrapol. intra-species dosimetric extrapolation to chronic exposure Chronic Exposure Level (rat)

31 Case Study 90-Day Rat Inhalation Studies with MWCNT and CNF, Exposure-Dose-Response Comparison Ma-Hock et al. (2009) Pauluhn (2010) Kasai et al. (2014) DeLorme et al. (2012) Material MWCNT (Nanocyl NC7000) MWCNT (Baytubes) MWCNT (MWNT-7) CNF (VGCF-H) Characterization Length/diameter, nm Impurities BET surf area, m 2 /g Packing dens, g/cm ,000 / % Al; <0.2% Co /10 ~0.5% Co / % / % Fe Exposure Conctr, mg/m 3 Ret. Lung Burden 0; 0.1; 0.5; 2.5 (NO) No 0, 0.1; 0.4; 1.5; 6 (NO) Yes 0; 0.2; 1; 5 (WB) Yes 0.54; 2.5; 25 (NO) No Response Lung weight (90 days) BAL PMN (90 days) + 1%; + 23%; + 81% Not reported +0; + 12; +27; +61% ~0.5; 3.8; 13; 19% +5; +17; +30% 0.6; 13.5; 45.7% -2; +8; ; 2.7; 11% Evaluation NOAEL LOAEL No 100 µg/m µg/m µg/m 3 No 200 µg/m µg/m µg/m 3

32 Case Study 90-Day Rat Inhalation Studies with MWCNT and CNF, Exposure-Dose-Response Comparison Ma-Hock et al. (2009) Pauluhn (2010) Kasai et al. (2014) DeLorme et al. (2012) Material MWCNT (Nanocyl NC7000) MWCNT (Baytubes) MWCNT (MWNT-7) CNF (VGCF-H) Characterization Length/diameter, nm Impurities BET surf area, m 2 /g Packing dens, g/cm ,000 / % Al; <0.2% Co /10 ~0.5% Co / % / % Fe Exposure Conctr, mg/m 3 Ret. Lung Burden 0; 0.1; 0.5; 2.5 (NO) No 0, 0.1; 0.4; 1.5; 6 (NO) Yes 0; 0.2; 1; 5 (WB) Yes 0.54; 2.5; 25 (NO) No Response Lung weight (90 days) BAL PMN (90 days) + 1%; + 23%; + 81% Not reported +0; + 12; +27; +61% ~0.5; 3.8; 13; 19% +5; +17; +30% 0.6; 13.5; 45.7% -2; +8; ; 2.7; 11% Evaluation NOAEL LOAEL No 100 µg/m µg/m µg/m 3 No 200 µg/m µg/m µg/m 3

33 Comparing MWCNT and CNF results with subchronic rat inhalation studies of two Benchmark compounds: ultrafine carbon black nickel subsulfide negative positive Benchmark particles

34 Lavage PMN, % Lung weight, % increase Exposure-Response Relationships 3-Month Inhalation Studies in Rats with MWCNT, CNF, CB and Ni 3 S 2 Endpoints: Lung lavage neutrophils and lung weight Exposure Concentration, mg/m : Exposure-Response Figure 9: and Exposure-Response Dose-Response relationships and Dose-Response Figure of 3-month 9: relationships Exposure-Response inhalation studies of 3-month and inhalation Dose-Respon stu with MWCNT, CNF and CB. A: Lung weight and lung lavage neutrophil exposurees. B: Lung weight dose-responses based on retained lung burden expressed as mass, xposure-response in rats with and Dose-Response MWCNT, CNF relationships and CB. A: in of Lung rats 3-month with weight MWCNT, inhalation and lung CNF studies lavage and neutrophil CB. A: expos Lung area WCNT, responses. B: Lung weight dose-responses based on retained lung burden expressed m and volume. CNF and - MWCNT CB. A: (Pauluhn, Lung weight 2010); and - lung responses. MWCNT lavage (Ma-Hock neutrophil B: Lung et al., exposure- weight dose-responses base 2009); : surface area and volume. - MWCNT (Pauluhn, 2010); - MWCNT (Ma-Hock et al., 200 F (DeLorme Lung weight et al., dose-responses surface area and volume. - MWCNT (Pauluhn, 2012); - CB (Elder based et on al., retained 2005). lung burden expressed as mass, nd volume. -- Ni CNF MWCNT 3 S 2 (DeLorme (Oberdörster (Pauluhn, et al., et al., 2010); 2012); unpublished); -- MWCNT CB (Elder - CNF (Ma-Hock et al., (DeLorme 2005). et al., et al., 2009); 2012); - CB (Elder e Lorme et al., 2012); - CB (Elder et al., 2005). ; - MWCNT (Kasai et al., 2014) Exposure Concentration, mg/m 3

35 Lung weight, % increase t, % increase Lung weight, % increase Lung weight, % increase Dose-Response relationships 3-month inhalation studies in rats with MWCNT, CNF, CB and Ni 3 S 2 Lung weight dose-responses based on retained lung burden expressed as mass, surface area and volume 100 Mass 100 Surface Carbon Black cm Retained Lung Burden, mg 5,000 10,000 Volume Retained Particle Volume, nl 100 Carbon Black 32,440 nl CNF 23,545 nl Retained Particle Surface Area, cm Day Inhalation, Male Rats: MWCNT Percent Increase of Lung Weight A As Function of Retained Lung Burd MWCNT Pauluhn 2010) MWCNT (Ma-Hock et al, 2009) Carbon Black (Elder, et al, 2005) Ni 3 S 2 (Oberdörster, unpub.data) CNF (DeLorme et al, 2012) MWCNT (Kasai et al, 2014)

36 Hazard Ranking of Different (Nano)-Materials Based on Different Metrics and Steepest Slope of Exposure-Dose-Response Relationships from Subchronic Rat Inhalation Studies (endpoint: lungweight increase) Metric Ranking Exposure Conc. : CNF = CB < MWCNT-K = MWCNT-P = MWCNT-MH < Ni 3 S 2 Retained Lung Burden: Mass: CNF = CB < MWCNT-P = MWCNT-K = MWCNT-MH < Ni 3 S 2 Surface area: CB < CNF = MWCNT-P = MWCNT-MH<MWCNT-K < Ni 3 S 2 Volume (bulk dens): CB < CNF = MWCNT-K < MWCNT-MH = MWCNT-P < Ni 3 S 2

37 Hazard Ranking of MWCNT and CNF against Benchmark Materials based on retained Particle Surface Area and Steepest Slope of Dose-Response Relationships from Subchronic Rat Inhalation Studies (endpoint: lungweight increase) Three Hazard Groupings: Low: CB < 0.3 % lungwt. incr./cm 2 Medium: MWCNT; CNF % lungwt. incr./cm 2 High: Ni 3 S 2 > 1.5% lungwt. incr./cm 2

38 Estimation of Chronic NOAEL from Subchronic Rodent Study using MPPD Model From: Oberdörster, 2002

39 Dosimetric Extrapolation of Inhaled Particles from Rats to Humans Rat (Multiple Path Particle Dosimetry Model) Human Exposure [mg(m 3 ) -1 ] Exposure (HEC) [mg(m 3 ) -1 ] Breathing Minute Volume Inhaled Dose [mg(kg) -1 ] Inhaled Dose [mg(kg) -1 ] Tidal Volume, Resp. Rate Resp. Pause Particle characteristics Anatomy Deposited Dose µg(cm 2 ) -1 ; Deposited Dose µg(cm 2 ) -1 ; µg(g) -1 µg(g) -1 Clearance Retention Regional Uptake (Metabolism, T½) Retained (Accumulated) Dose [µg(g) -1 ; µg(cm 2 ) -1 ] Effects Assumption: If retained dose is the same in rats and humans, then effects will be the same

40 Estimation of HEC through BMD analysis of subchronic rat studies by using rat responses as 1 St. Dev. or as 10 % above control (BMCL). Endpoint: LUNG WEIGHT Increase Material Rat Human s u b c h r o n i c c h r o n i c c h r o n i c BMDL BMCL Daily Daily BMCL BMDL BMDL Daily HEC µg/lung µg/m 3 Depos.Dose Depos.Dose µg/m 3 µg/lung µg/alv. Depos.dose µg/m 3 µg/6 hr µg/6 hr compt. µg/8 hr (depos.fract) (depos.fract) MWCNT(P) ,000 8, (0.022) (0.073) MWCNT(M) ,830 2, (0.019) (0.062) CNF ,083 5, (0.022) (0.064) CB , ,375 1, (0.024) (0.076) Ni 3 S ,483 1, (0.034) (0.109) MWCNT and CNF cannot be categorized as PSP Human breathing conditions: light exercise; TV: 1024 ml; BrFreq: 20 min -1 ; 8 hr; oro-nasal breathing

41 REL: Fine: 2.5 mg/m 3 Nano: 300 µg/m 3 REL: 1 µg/m 3

42 CHALLENGES FOR ESTABLISHING Occupational Exposure Levels (OEL) FOR CNT/CNF: Workplace monitoring: 1 µg/m 3 ; distinguishable from background? One generic OEL for all: Are all CNTs and CNFs toxicologically of equal potency? In addition to dimension, surface modification or functionalization, tangles, straightness, level of impurities, surface defects are known to alter toxicity: MWCNT-x MWCNT-y However, with no convincing data to the contrary, it is prudent to treat airborne CNTs/CNFs as hazardous Needed: Results of chronic rodent inhalation study

43 Risk Assessment and Risk Management Paradigm For Engineered Nanoparticles (NPs) Physico-chemical Properties! Adverse NP Effect: at portal of entry and remote organs Experimental Animals Biokinetics! Humans Alternative Models Exposure-Dose- Response Data In Vivo Studies (acute; chronic) In Vitro Studies (non-cellular) (animal/human cells) (subcellular distribution) Dose-Metric! Inhalation Ingestion, Dermal Biological Monitoring (markers of exposure) Occupational/ Environmental Monitoring LCA! Dosimetry Risk Calculation Susceptibility Extrapolation Models (high low) (animal human) Mechanistic Data Public health/social/ economical/political consequences Regulations Expos. Standards Prevention/Intervention Measures Biomed./Engineering Assessment Factors

44 Desirable as basis for testing and for regulatory hazard and risk characterization: Establishing toxicologically well defined Benchmark Materials as tool for classification

Lang Tran Institute of Occupational Medicine Edinburgh, UK

RISK ASSESSMENT OF ENGINEERED NANOMATERIELS Lang Tran Institute of Occupational Medicine Edinburgh, UK NanoSafety and NanoCode Project Outputs, Prague 1 st November 2011 STRUCTURE OF THE TALK Exposure