Welding Fumes & NP Exposures

Transcription

1 Welding Fumes & NP Exposures Nanotoxicity: New Threats to Occupational and Environmental Health? Jong Sung Kim, MSc, PhD, Assistant Professor & Director of HERC Laboratory Department of Community Health & Epidemiology Department of Microbiology & Immunology Faculty of Medicine, Dalhousie University

2 DECLARATION OF CONFLICT OF INTEREST I do not have an affiliation (financial or otherwise) with a pharmaceutical, medical device, or communications organization, or other for-profit funder of this program. I do not intend to make therapeutic recommendations for medications that have not received regulatory approval.

3 CONTENTS Topics I will discuss: Nanotechnology Awareness What is Nano & What s so Special about the Nanoscale? Nanotechnology Applications & Potential Impacts Current Research: Nanoparticle Toxicity Assessment Case Report (Human Exposure) In Vivo Model (animal study) In Vitro Model (human lung cell study)

4 LEARNING OBJECTIVES Following this session, participants will be able to: describe the benefits, unique properties and applications of nanomaterials. understand the potential occupational and environmental health risks associated with nanomaterials. identify current the state of hazard surveillance for workers potentially exposed to nanomaterials.

5 DALHOUSIE HERC LABORATORY Analytical instrumentation: LC-MS, ICP-MS, GC-MS, HPLC, IC HERC Laboratory was established as one of three national centres (UT, Dalhousie, UBC) to enable a collective study of climate, air quality, population exposures, and human health. It was created using research awards and matching resources ($4.2 million) from the Canada Foundation for Innovation (CFI), the Nova Scotia Research and Innovation Trust (NSRIT), Dalhousie Faculty of Medicine, and industrial partners.

6 DALHOUSIE HERC LABORATORY

7 RESEARCH PROGRAM To better understand how emerging hazards and exposures lead to adverse health outcomes at various levels of biological organization (from cellular and molecular levels to populations) and how human body modify these responses to maintain homeostasis (host-defense). Healthy environments for healthy people

8 WHAT WE DO Advance knowledge of the relationship between health and the environment (evaluating, tracking, and preventing health hazards). Hazard Improved health Data Stakeholders* Exposure Dissemination Prevention Health outcome *Stakeholders include: Governmental agencies academia, health care system, policy makers, media public, business & industry, non-governmental organizations We have features for every step of the way

9 WHERE WE LIVE? EMERGING RISKS High tech washroom High tech rain

10 WHERE WE LIVE? EMERGING RISKS Nanotechnology is seen as the way of the future will bring a lot of benefits nothing is ever perfect! Cartoon source:

11 Harris Poll was conducted online within the US between Jun. 18 & 25, 2012 among 2,467 adults (aged 18 and over), data from The Harris Poll #52, Sep. 6, 2012 NANOTECHNOLOGY AWARENESS How much have you heard about nanotechnology? Have heard at least a little: 38% (net)

12 NANOTECHNOLOGY AWARENESS Based on what you know, how would you describe the relative risks and benefits of nanotechnology? - Base: Have heard at least a little about nanotechnology (38%) Harris Poll was conducted online within the US between Jun. 18 & 25, 2012 among 2,467 adults (aged 18 and over), data from The Harris Poll #52, Sep. 6, 2012

13 WHAT IS NANO? nm Nano is a prefix that comes from the Greek word for dwarf. It simply means one billionth (1 nm = 10-9 m). Materials designed and produced to have structural features with Nanoscale Source: National Nanotechnology Initiative (NNI) Think really, really small

14 WHAT S SO SPECIAL ABOUT THE NANOSCALE? Nanoscale-associated behavior Scale at which Quantum Effects dominate properties of materials - The materials properties change at the nanoscale (quantum effects). - Size-dependent properties are the major reason that nanoscale objects have such amazing potential. Source: National Nanotechnology Initiative (NNI)

15 WHAT S SO SPECIAL ABOUT THE NANOSCALE? Nanoscale-associated behavior Scale at which surfaces & interfaces play a large role - Nanomaterials have far larger surface areas than larger-scale materials. - As surface area of a material increases, a greater amount of the material can come into contact with surrounding materials, thus affecting reactivity. High Surface area to volume ratio S.A.=h*w*# 6 cm 2 = (1 cm) 2 * 6 60 cm 2 = (1/10 cm) 2 * 6 * *10 7 cm 2 = (1/10 cm) 2 * 6 * 10 9 Surface area increasing Source: National Nanotechnology Initiative (NNI)

16 WHAT S SO SPECIAL ABOUT THE NANOSCALE? Higher Surface area to volume ratio NMs can be made to be stronger, lighter, more durable, waterrepellent, antimicrobial, self-cleaning, better electrical conductors among other traits. Benefits of Small Systems Doing more with less Multi-functionality New applications Quicker performance Better performance

17 NANOTECHNOLOGY GROWTH MARKET Source: Source: It is necessary to develop high-throughput in vitro toxicity screening to assess NP safety as a predictive in vivo toxic potential due to the concerns about the safety of a growing number of NPs.

18 NANOTECHNOLOGY APPLICATIONS US $76 billion by 2020 NT Applications Source: National Nanotechnology Initiative (NNI)

19 NANOTECHNOLOGY APPLICATIONS Source: Risk Science Center, University of Michigan School of Public Health

20 NANO RISK? Nanotoxicology

21 POTENTIAL HEALTH IMPACTS The Bio-Nano Interface: Nanoparticle-Bio Interactions Scale at Which Much of Biology Occurs - Hemoglobin, the protein that carries oxygen through the body, is 5.5 nm in diameter. - A strand of DNA, one of the building blocks of human life, is only about 2.5 nm in diameter. Interfacing engineered NPs with biological systems: Anticipating adverse nano-bio interactions Source: National Nanotechnology Initiative (NNI)

22 POTENTIAL HEALTH IMPACTS Risk = Function of Hazard and Exposure. Human exposure to NPs: skin (dermal), lungs (inhalation), gastrointestinal tract (ingestion), or by injecting as a formulated medicine. The most critical concern over health & environmental effects: when NPs are aerosolized (highly mobile & enter the human body via inhalation). Source: Card et al (2008) Am J Physiol Lung Cell Mol Physiol 295: L

23 OCCUPATIONAL HEALTH RISKS OF NPs? Do occupational exposures to engineered nanoparticles (NPs) pose an unintended risk of adverse health effects? Workers are already engaged in processes in which they may be exposed to NPs. Workers are on the frontlines of NP exposure, but occupational health risks of NPs are not yet clearly understood. As with any new material being developed, scientific data on the health effects in exposed workers are largely unavailable (e.g., asbestos). This in turn has brought up the assessment and prevention of exposure and its risk at workplaces. We do not fully know how these NPs may enter the body, where they may travel once inside, or what effects they may have on the body s systems. We do not fully know whether or how effects may differ for chemically or structurally different particles at the nanoscale.

24 WELDING FUMES Welding fumes consist of metallic oxides generated by the heating of metal being welded. The metal particles depend on the base metal and materials used as the welding rods or coatings (Mn, Fe, Cr, Ni, Cd, Zn). Workers may inhale the welding fumes, which could potentially lead to adverse health effects (neurotoxicity, metal fume fever, chronic obstructive pulmonary disorder, lung cancer). International Agency for Research on Cancer (IARC): Group 2B, possibly carcinogenic to human. Exposure limit: ACGIH (8-hour TWA of 5 mg/m 3, measured as total particulate in the welder's breathing zone) Based on Mass!?

25 NPs in Welding Fumes A recent welding fume characterization study at the breathing zone across welders (n=20) indicated 92% of the particles were <100 nm, with 50% of the particles <41 nm. Inhalation of these metal fume NPs can result in particle deposition onto the alveolar epithelial surface of the lungs, compromising the respiratory and circulatory systems. Graczyk, H., et al., Characterization of Tungsten Inert Gas (TIG) Welding Fume Generated by Apprentice Welders. Annals of Occupational Hygiene, (2): p

26 NANO RISK ASSESSMENT Issue forming Hazard Identification Dose Response Reliable assessment of human exposure from environmental & incidental exposures Role of susceptibility (age, gender, disease, genetic) factors in human risk assessment Risk Characterization Exposure Assessment Population Health/Epidemiology Study Risk Management Policy or regulation

27 NANO RISK ASSESSMENT Raw materials Don t know what nanomaterial is. Manufacturing Better products, but what about worker? Life Cycle Stages Life Cycle Assessment At end-of-life, where do they go? Disposal Use Nanotechnology can be good, if regulated properly.

28 TOXICITY TESTING MODELS Nanoscaleassociated behavior Nanomaterials In Vitro (Cells) Study In Vivo (Animal) Study very limited information on human exposure conventional toxicology approaches Human

29 HUMAN EXPOSURE STUDY The potential occupational health risks associated with engineered nanomaterials Role of metal oxide NPs in histopathological changes observed in the lung of welders. Andujar et al., 2014, 11:23, Particle and Fibre Toxicology.

30 HUMAN EXPOSURE STUDY No human toxicological data is currently available. Welders with various adverse respiratory outcomes as a model population of occupational exposure to NP. Aim: to evaluate if welding fume-issued NP could be responsible, at least partially, in the lung alterations observed in welders. Methods: A combination of imaging and material science techniques was used to characterize NP content in lung tissue from 21 welders and 21 matched control patients.

31 ROLE OF METAL NPs IN THE LUNG OF WELDERS Elemental mapping of lung tissue sections. Figure A shows typical elemental maps obtained for Fe (blue) and Mn (red) in control patients and welders. A significant overload of Fe, Mn, Cr essentially in welders. Figure B: Quantification of the signal obtained for each element Open circles: Controls Black squares: Welders

32 ROLE OF METAL NPs IN THE LUNG OF WELDERS Identification of NP in lung tissue homogenates. STEM-EDX (Scanning Transmission Electron Microscopy-Energy Dispersive X-Ray): to characterize the size and chemical nature of the particles present in the pulmonary samples (lung tissue homogenates) Size of particles (20 25 nm individual diameter, A) and the chemical nature (Fe, Mn, Cr essentially) and the co-localization of the chemical signals (EDX analysis, B).

33 ROLE OF METAL NPs IN THE LUNG OF WELDERS Mineralogical analysis of lung tissue homogenates. These experiments confirmed the metallic overload in welder s lung and identified a significantly higher mass concentration of total mineral and especially metallic particles in welders.

34 PULMONARY TOXICITY ASSESSMENT In Vivo Model (using animals) Allow realistic route with reproducible NP dosing & lung distribution Inhalation & instillation exposures General Components of the Pulmonary Bioassay Bronchoalveolar lavage fluid evaluation Cell differential analysis Lactate dehydrogenase Cytokine/chemokines Lung tissue analysis Lung histopathology Dosimetry Enzyme activity

35 BRONCHO ALVEOLAR LAVAGE (BAL) Saline solution A saline wash of the airways (broncho) and air sacs (alveolar) for recovery of inflammatory cells. Indicate inflammatory responses and cytotoxicity induced by toxicant Fluids Cells Cytokines/chemokines, total protein & lactate dehydrogenase (LDH) Total cell & Differential cell counts (macrophages, neutrophils, lymphocytes etc)

36 IN VIVO NANOTOXICOLOGY Human exposure to NPs & environmental bacteria can occur simultaneously. The purpose of this study was to determine if host defense against bacterial infection is enhanced or impaired by Cu NPs in a murine pulmonary infection model.

37 BRONCHO ALVEOLAR LAVAGE (BAL) Schematic of the pulmonary bacterial clearance model. We established a murine pulmonary infection model of Klebsiella pneumoniae (K.p.) to determine if pulmonary bacterial clearance is impaired by NP exposure. Following both sub-acute inhalation and intratracheal instillation, mice were intratracheally challenged with K.p. bacteria at a dose of 1.4 ± CFUs/mouse.

38 BRONCHO ALVEOLAR LAVAGE (BAL)

39 BRONCHO ALVEOLAR LAVAGE (BAL)

40 BRONCHO ALVEOLAR LAVAGE (BAL)

41 IN VITRO MODEL IN NANOTOXICOLOGY In vitro assays can serve as a screening method for assessing NP toxicity. opportunity for extensive investigation of (can t be conducted in vivo). Alternative and the 3 Rs (Replace, Reduce, Refine) In Vitro Exposure of Lung Cells to Nanoparticles Submerged System Particle suspension in medium & Exposure of immersed cells Air-Liquid Interface (ALI) Air delivery of NPs to lung cells at the ALI

42 NP INTERACTION WITH ALVELOAR EPITHELIUM into the systemic circulation is most likely to across with its very large surface area (>100 m 2 in humans) and thin barrier thickness. However, interactions between Source: Card et al (2008) Am J Physiol Lung Cell Mol Physiol 295: L

43 LIMITATIONS: IN VITRO STUDY Conventional in vitro study: Need new approach Proteins Agglomeration Drawbacks Not mimicking alveolar epithelial conditions in vivo. Interaction between NPs & media. Uncertainty of dosimetry. NP agglomeration/dispersion problems. Air-Liquid Interface Exposure Transwell NPs Airway Surface Liquid (ASL) Apical side: Lung cells Medium Cells Semi-permeable Membrane Exposure chamber Basolateral side: Medium

44 IN VITRO NANOTOXICOLOGY The objective of this study was to overcome the limitations of conventional in vitro exposure of submerged lung cells to NPs for NP toxicity assessment. We developed a dynamic in vitro exposure system (DIVES) capable of generating and depositing airborne NPs directly onto lung cells at an ALI (simulation of human pulmonary exposure to NPs).

45 Air Aerosol Inlet Cell culture insert Cells on membrane Culture medium Air out Cellular Responses Air out

46 NANOPARTICLE IN VITRO EXPOSURE SYSTEM (Vitrocell) Figure: A Schematic of a NP In Vitro Exposure System. This in vitro approach simulates particle deposition in the human lung more realistically than does submerged cell exposure (without an apical air interface), and it preserves the inherent properties of the particles.

47 NANOPARTICLE IN VITRO EXPOSURE SYSTEM

48 NANOPARTICLE SIZE DISTRIBUTION

49 CELL VIABILITY (AB ASSAY)

50 INTRACELLULAR ROS

51 Streptococcus pneumoniae (S.p) Infection (Invasive Pneumococcal Disease, IPD) Member of the streptococcus family Gram positive diplococci Exposure to welding fumes increase the risk of S.p infections in welders. Pneumonia was associated with a reported occupational exposure to metal fumes in the previous year (OR = 1.96). To date, the mechanism by which welding fumes increase susceptibility to S.p infection is not well known. Are the metal NPs in the welding fumes to blame? Big picture question: What are the underlying mechanisms that make S.p pathogenic and cause disease? What makes certain people/groups susceptible?

52 S.P DISEASE BURDEN Goal: to determine the relationship between metal NP exposure (e.g.: copper) and the increased susceptibility of welders to infection by Streptococcus pneumoniae. Do copper NPs promote cytotoxicity in human alveolar epithelial cells (A549 cells) to enhance adhesion of S.p? S.p adhesion to lung cells is increased after Cu NP exposure

53 OCCUPATIONAL HEALTH SURVEILLANCE (OHS) Current the state of occupational health surveillance for workers potentially exposed to nanomaterials. Medical surveillance Hazard surveillance Interim Guidance for Medical Screening and Hazard Surveillance for Workers Potentially Exposed to Engineered NPs. US Centers for Disease Control and Prevention (CDC) National Institute for Occupational Safety and Health (NIOSH)

54 MEDICAL SCREENING & HAZARD SURVEILLANCE Purpose: to provide interim guidance about whether specific medical screening, including performing medical tests on asymptomatic workers, is appropriate for these workers. Currently there is insufficient scientific and medical evidence to recommend the specific medical screening of workers potentially exposed to engineered NPs. Even though the evidence is currently insufficient to recommend specific medical screening of workers, it is possible to consider screening in specific situations. For example, if specific medical detection exists for the same substance in larger dimensions, this could also apply to NP. Interim Recommendations: Taking measures to control workers exposure to NPs; Conduct hazard surveillance as the basis for implementing controls; Continue use of established medial surveillance approaches.

55 SUMMARY Nanotech brings benefits as well as potential risks NPs are dominant in welding fumes and detected in the lung tissues in welders. NP exposure induced an impairment in host defense against bacterial infection. Thus, NP exposure may lead to increased risk of pulmonary infection by impairing host defense against bacteria. Diverse stakeholders have agreed that research to address these questions is essential for the responsible development of safe nanotechnology.

56 ACKNOWLEDGEMENT Contact: Dr. Jong Sung Kim, Laboratory Director Tel: The Power of Innovation!

57 FUNDING SOURCES