Basics of nanotoxicology. Occupational safety and health in practice Example new technologies: nanomaterials. Presentation No 2

Transcription

1 Developing Reference Methods for Nanomaterials Occupational safety and health in practice Example new technologies: nanomaterials Presentation No 2

2 Imprint This presentation is a final product of the project NanoValid - project F and was generated under the lead responsibility of Miriam Baron (Federal Institute for Occupational Safety and Health). The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/ ) under grant agreement n (NanoValid Development of reference methods for hazard identification, risk assessment and LCA of engineered nanomaterials). The responsibility for the contents of this publication lies with the authors. Copyright 2015 by the authors Project monitoring and main author: Miriam Baron Federal Institute for Occupational Safety and Health (BAuA) With contributions from: Rolf Packroff, Michael Roitzsch, Dag Rother, Aart Rouw, Torsten Wolf Federal Institute for Occupational Safety and Health (BAuA) Shashi Singh Centre for Cellular & Molecular Biology Damjana Drobne University of Ljubljana Figures: Miriam Baron Federal Institute for Occupational Safety and Health (BAuA) Fox / Uwe Völkner Project support: Elke Kahler-Jenett, Katharina Niesmann Federal Institute for Occupational Safety and Health (BAuA) Design: Carolin Schneider, eckedesign Berlin Editing: Johanna Ebbeskotte, Markus Flender Federal Institute for Occupational Safety and Health (BAuA) Publisher: Federal Institute for Occupational Safety and Health (BAuA) Friedrich-Henkel-Weg 1-25, Dortmund, Germany Nöldnerstr , Berlin, Germany Telephone NanoValid: Project Coordinator: Rudolf Reuther, Nordmiljö AB rudolf.reuther@enas-online.com Telephone (Sweden) or (Germany) All rights reserved, including photomechanical reproduction and the reprinting of extracts. First published: July

3 Slide 1: How large is the Occupational Safety and Health problem regarding nanomaterials from the view of safety experts? How does the size of the particles affect the risk? Does the risk end at 100 nm or do we have to consider other ranges? Is there only a problem with nanomaterials or do we need to broaden our focus to respirable dusts and fibres? Are nanomaterials more toxic and carcinogenic and, if yes, how does this change the control strategy? 3

4 Slide 2: Overview The complex world of nanomaterials Challenge for occupational safety Hazard Potential Information gathering Derivation of control strategies and safe design of workplaces Exposure assessment Risk assessment Toxicology 2 In my previous talk, I gave you an insight into the complex world of nanomaterials. Nanomaterials are various. The control strategies for workplaces need to be adapted accordingly. Now I will elaborate on the aspect of toxicology. Toxicology is a strong pillar for risk assessment. All these factors are required to adequately derive control strategies and safe design of workplaces. 4

5 Slide 3: Nanotoxicology Particle toxicology respirable dusts (granular, biopersistent) WHO fibres (long, thin, biopersistent) Route of exposure: Inhalation Inflammatory responses Carcinogenicity nano Chemical toxicology Specific toxic effects (CLP criteria for classification) Route of exposure: Inhalation, skin All negative adverse effects of chemicals on health Adverse effects, which are specific for nanomaterials, are not known yet. 3 We can distinguish between particle toxicology and chemical toxicology. There is a problem with fibres (if they have a certain size and are biopersistent) We have exposure routes via inhalation and via the skin. Until now, no new hazardous effects specific for nanomaterials are known. 5

6 Slide 4: Toxicokinetics Do nanoparticles distribute better in the body than larger particles? Several exposure routes: dermal (skin), inhalation (lungs), oral (intestine) Mainly no free primary particles (stick together) : half life of the free particles in inverse ratio to the particle concentration and proportional to the particle size (Preining, 1998) Half life Conc. + Size 4 Which issues do we need to consider if we talk about potential health risks? What is of particular importance there? The physical structure Are nanoparticles better able to distribute in the body than larger particles? Several exposure routes: dermal (skin), inhalation (lungs), oral (intestine) In most cases, there are no free primary particles (stick together) since the half-life of the free particles is in inverse ratio to the particle concentration and proportional to the particle size (Preining, 1998). As a general rule, we find aggregates and agglomerates. 6

7 Slide 5: Distribution of particles: counter-example Can nanoparticles systemically distribute through cell membranes and cause damage? Post mortem samples of stone coal miners (LeFevre et al., Hum Pathol, 1982, 13(12):1121-6) Stone coal particles, including not nanoscale Pigments found in liver and spleen No parallel histopathological changes Not only nanoparticles show a certain systemic availability and distribute in the body to a certain extend! 5 What if nanomaterials penetrate cells? Can they distribute through cell membranes and cause damage? Maybe this is a new toxicokinetics? There are studies on non-nanoparticles regarding the cell penetration topic. One of them is a study with post mortem samples of stone coal miners. In this study, a moderate to severe pigment accumulation in liver (10 % of the samples) and spleen (19.5 % of the samples) was found, but there were no parallel histopathological changes in these tissues. This means that the coal particles caused no disease in this study. One can conclude that not only nanoparticles show a certain systemic availability and distribute in the body to a certain extent larger particles do this as well. 7

8 Slide 6: Toxikokinetics: dermal exposure Example: Australian study (Gulson et al., 2010), ZnO in sun screen, primary particles 19 nm and 110 nm Experiment: twice a day, 5 days on the beach, Sydney Measurement: < 0,001 % of the incorporated 68 Zn in blood, both forms systemically available, nanoscaled ZnO slightly better presumably due to better solubility Conclusion: to a low extent irrelevant dermal uptake 6 Example: Australian study (Gulson et al., 2010), ZnO in sun screen, primary particles 19 nm and 110 nm Experiment: twice a day, 5 days on the beach, Sydney Measurement: < 0.001% of the incorporated 68 Zn in the blood, The toxicologists say that both forms are systemically available to a very low extent. Nanoscaled ZnO particles are slightly better soluble presumably due to better solubility. Conclusion: To a low extent, we find irrelevant dermal uptake both from nanoscaled and macroscaled particles. 8

9 Slide 7: Toxikokinetics: inhalation exposure Example: Inhalation study with nanoscaled manganese oxides: primary particles 3-8 nm, agglomerates 30 nm Experiment: rats, days, 6 h/d Increase of the tumor necrosis factor alpha in brain However: parallel experiment with manganese oxides and well soluble MnCl 2, same result Manganese oxides not completely insoluble No particle toxicity: well-known neurotoxic effects of manganese: released ions 7 Example: Inhalation study with nanoscaled manganese oxides: primary particles 3-8 nm, agglomerates 30 nm Experiment: rats, days, 6 h/d As a matter of fact, an increase of the tumor necrosis factor was found However: in a parallel experiment with manganese oxides and well soluble MnCl 2, a comparable result was obtained. Manganese oxides are not completely insoluble. Here, we have no effect attributable to particle toxicity, but rather to the well-known neurotoxic effects of manganese, which released ions. 9

10 Slide 8: Higher carcinogenic potency than conventional materials? Metaanalysis of studies on inhalation carcinogenicity with rats (nano: 3 studies, micro: 4 studies, diesel engine emissions: 11 studies) Several corrections required, i.e. exposure ( h / d, d / week, month) and the total length of the study (tumor development depends on age) Difference in potency: Carcinogenic potency of respirable nanoscaleddusts ~ 2.5times higher 8 Meta-analysis of studies on inhalation carcinogenicity with rats (nano: 3 studies, micro: 4 studies, diesel engine emissions: 11 studies) Several corrections required, for instance concerning the duration of exposure (h/d, d/week, month) and the total length of the study (tumor development depends on age) Difference in potency: GBD (granular biopersistent dusts) nanomaterials have a carcinogenic potency which is ~ 2.5 times higher than the macroscaled particles 10

11 Slide 9: How much is 2.5? substance Cancer risk 4:10000 mg/m 3 Benzo(a)pyren 0.07 NDMA Acrylamide 70 MDA 70 Ethylenoxide 200 Acrylnitrile 260 1,3-Butadien 500 Trichlorethen Maximal difference in potency: negligible 9 Regarding the carcinogenic potency, we already find very large differences between different chemicals, that is to say, differences in the order of magnitudes. Compared to this range, 2.5 is, so to speak, almost nothing. 11

12 Slide 10: Where are the toxicologists worried? 1. Dust effects Respirable dust enters the deep airways Macrophages and their job Accumulation due to slow removal of biopersistent dusts Oxidative stress and inflammation 10 Why is respirable dust so problematic? Respirable dust means very fine dust that can enter the deep airways. Normally, alveolar macrophages have the job to clean material from our deep airways. In the upper airways, we have cilia, little hairs, which transport the dust out of the airways. There you can swallow the dust, but in the deep airways, we have only these cells which normally phagocytose bacteria or dusts. If we inhale a lot of respirable dust, which is biopersistent, it accumulates in the deeper airways, since the removal is too slow. The macrophages which are specialised on bacteria, remove the dust. However, if more than 6 % of the volume of the macrophages is loaded with particles, they react with oxidative stress. Inflammation processes are the result of an overload of the deep airways. The inflammation mostly starts at bifurcations where a higher amount of dusts is deposited. Here we have a general problem with respirable dust which is not restricted to the nanoscale. 12

13 Slide 11: Where are the toxicologists worried? 1. Fibre effects Rigid, insoluble WHO fibres (length > 5 µm, diameter < 3 µm, rigid) Example: asbestos Frustrated phagocytosis External inflammation Chronic inflammation, tumours Problem does not stop at the 100 nm size mark 11 If a fibre is rigid, stiff and longer than the alveolar macrophage that takes it up, this causes problems. Some fibres are so long that if the macrophage tries to phagocytose it, it is not able to do so. This is called frustrated phagocytosis. Then this macrophage reacts with external inflammation. This external inflammation leads to lung tissue damage and in case of a chronic inflammation, it may eventually cause lung tumours. Also, these fibres have the ability to migrate out of the lung into the mesothelia. The mesothelia are tissues which align the lung and also our inner organs. In consequence, the fibres can also get stuck in the mesothelia where macrophages can likewise come and try to remove them. Since removal of the fibres is not possible, chronic inflammation and, in consequence, tumour development can also occur in the mesothelia. This is known as the asbestos problem. However, it is not limited to asbestos. In fact, all rigid nanofibres with similar morphology cause concern. Here, we do not have a specific nanomaterial problem, which ends at the 100 nm size mark. Rather, this issue depends on the biopersistence and the morphology. 13

14 Slide 12: Conclusions As always and for every chemical there will be open questions left Like for many other chemicals, we still find knowledge gaps regarding the health risks. We want to recognize the risks at an early stage. Many questions already answered Scientific knowledge on fine- and ultrafine dusts, fibres and chemical substances is a good starting point. Risk assessmentstrategies can be developed Nanomaterials can have different hazardous potentials (effect and release potential) Nanoscaled cannot be equated with hazardous. It is the respirable (nano-)dust that matters most! For occupational safety, the precautionary approach and the classical dust safety strategies are a good basis. 12 Many relevant questions are answered. The scientific knowledge on fine- and ultrafine dusts, fibres and chemical substances forms a good starting point for evaluating the health risks of nanomaterials. 14

15 Slide 13: Thank you! Thank you for your attention! 13 15