Potential bio-accumulation of nanoscale particles. • Accumulation of a substance within a species can occur due to lack of degradation or excretion. • Many nanoparticles are not biodegradable. • If nanoparticles enter organisms low in the food web, they may be expected to accumulate in organisms higher in the food web. Very little is understood about possible health effects of nanoparticle exposure
Potential human hazards for nanoscale particulates. Inhalation: Inhaled particles induce inflammation in respiratory tract, causing tissue damage. Example: Inhalation of silica particles in industrial workers causes “silicosis”. Dermal exposure: Particles may enter body through the skin. Potential hazards are unknown at present. Ingestion: nanoparticles may cause liver damage. Ingested nanoparticles (i.e. for oral drug delivery) have been found to accumulate in the liver. Excessive immune/inflammatory responses cause permanent liver damage. Other: ocular, ….
Potential bio-uptake of nanoscale particulates. • Nanoparticles may enter living cells via: – Endocytosis • Receptor activation for initiation – Membrane penetration • Generally occurs with very hydrophobic particles – Transmembrane channels • May be seen with very small nanoparticles (< 5 nm?)
Possible Health EffectsInhalationPulmonary inflammatory reaction – Persistent inflammation is likely to lead to diseases such as fibrosis and cancer. Thus it is important to control inflammation. This can be done if we can: - (i) determine the critical dose of particles that initiates inflammation and - (ii) set exposure limits, according to the relevant metric, so that such a dose cannot be reached within a lifetime exposure scenario.
Wahrheit (Dupont), January 2004. Optical micrograph of lung tissue from a rat exposed to single- wall carbon nanotubes (1 mg/kg) 1 week post exposure. Note the early development of lesions surrounding the instilled SWCNT (arrows) and the nonuniform, diffuse pattern of single-wall carbon nanotube particulate deposition in the lung (X 100). Low-magnification micrograph of lung tissue from a rat exposed to single-wall carbon nanotubes (1 mg/kg) at 1 month postinstillation. Note the diffuse pattern of granulomatous lesions (arrows). It was interesting to note that few lesions existed in some lobes while other lobes contain several granulomatous lesions—and this was likely due to the nonuniform deposition pattern following carbon nanotube instillation. Magnification X 20. Higher magnification optical micrograph of lung tissue from a rat exposed to single-wall carbon nanotubes (1 mg/kg) at 1 month postinstillation exposure. Note the discrete, multifocal mononuclear granuloma centered around the carbon nanotube material (arrows). Magnification X 400. D. B. Wahrheit et. al. Toxilogical Sciences 77, 117-125 (2004)
Concerns about granulomas and fibers. Granulomas (miscropic nodules), consisting of particles, live and dead cells, and debris and could impair cellular and physiological (gas exchange) lung functions and give rise to fibrosis, more defined nodules, and other lesions. Fibers are generally of more health hazard than other forms of particulates. It is well established that the pathogenicity of a fiber in the lungs directly correlates with its biopersistency(Oberdorster 2000). NTs are totally insoluble and probably one of the most biologically nondegradable man-made materials.Determining how the NT-induced granulomas progress would require a longer- duration study with this biopersistent material.
Observations and tentative conclusions. • Granulomas were observed in lungs 7 d or 90 d after an instillation of 0.5 mg NT per mouse (also in some with 0.1 mg); • NT, regardless synthetic methods, types and amounts of residual catalytic metals, produced granulomas; • Lung lesions in the 90-d NT groups, in most cases, more pronounced than those in the 7-d groups. • Our study shows that, on an equal-weight basis, if carbon nanotubes reach the lungs, they are much more toxic than carbon black and can be more toxic than quartz, which is considered a serious occupational health hazard in chronic inhalation exposures. • If fine NT dusts are present in a work environment, exposure protection strategies should be implemented to minimize human exposures.
Control of NanoparticlesExposure by inhalation- Filtering respirators or air supplied respirators may be used as a last option to control exposure to nanoparticles.- Probably the efficiency will be high for all but the smallest nanoparticles (less than 2 nanometers).- The respirator must fit properly to prevent leakage. The white powder around the nostrils shows that this mask did not have a tight fit.
Possible Health EffectsIngestionNanoparticles can be swallowed and therefore available for transfer to otherbody organs via the gastro-intestinal compartment.There is also some evidence that smaller particles can be transferred morereadily than their larger counterparts across the intestinal wall (Behrens et al;2002).Little is currently known about the health effects of nanoparticles on the liverand kidneys as well as the correct metric for describing the nanoparticle dosein these organs.Another area which merits further research is the transfer of nanoparticlesacross the placenta barrier. Exposure to nanoparticles during the criticalwindow of fetal development may lead to developmental damage in theoffspring.
Control of NanoparticlesIngestion exposure- Occurs from hand-to-mouth contact- Control by using gloves when handling nanoparticle products- Hand washing before eating, drinking or smoking is also important
Possible Health EffectsDermal exposure• Harmful effects arising from skin exposure may either occur locally within the skin or alternatively the substance may be absorbed through the skin and disseminated via the bloodstream, possibly causing systemic effects.• Dermal absorption of ultrafine particles (nanoparticles) has not been well investigated and suggested that ultrafine particles may penetrate into hair follicles where constituents of the particles could dissolve in the aqueous conditions and enter the skin. Direct penetration of the skin has been reported by Tinkle et al (2003) for particles with a diameter of 1000 nm, much larger than nanoparticles.• It is reasonable to postulate that nanoparticles are more likely to penetrate, but this has not yet been demonstrated. Several pharmaceutical companies are believed to be working on dermal penetration of nanoparticles as a drug delivery route.
Control of Nanoparticles Skin Exposure• Skin penetration may occur mainly in the later stages of the process, recovery or surface contamination.• Some evidence shows that nanoparticles penetrate into the inner layers of the skin and possibly beyond, into the blood circulation.
Environmental Fate/Transport and Environmental Toxicity Examples of specific effects Nanomaterials TestedStudy focus investigatedAquatic fate Impact on water migration through alumina, magnetite, nanofibers, silicon soil, chemical behavior in carbide, silicon dioxide (SiO2), single walled estuarine systems, fate in potable nanotubes (SWNT), titanium dioxide (TiO2), water, uptake by aquatic organisms zinc oxide (ZnO)Environmental Microbial biomass, organic carbon cadmium celenide (CdSe), cupric oxidetoxicity assimilation rates, deposit (CuO), iron oxide (Fe2O3), molybdenum feeding, uptake, estuarine disulfide (MoS2), nanofibers, quantum dots, invertebrates, toxicity in drinking silicon dioxide (SiO2), single walled water, fish, frogs, bacteria, fungi, nanotubes (SWNT), titanium dioxide (TiO2), daphnia, algae zinc oxide (ZnO)Fate in air Emission minimization, sampling fullerenes, silicon dioxide (SiO2), single and analysis, nucleation rate walled nanotubes (SWNT) sulphuric acid (H2SO4)Fate in Desorption and release from aluminum oxide (Al2O3), cadmium celenidesoils/sediment nanoparticle surfaces, disposition (CdSe), hyroxylated fullerenes, magnetite of contaminants,Cross media Effects of oxygen, chlorine, UV carbon nanofibers, fullerenes, titaniumfate/Transport light dioxide (TiO2), zinc oxide (ZnO)
Health Effects: Many questions, not many answers. • In what ways might employees be exposed to nanomaterials in manufacture and use? • In what ways might nanomaterials enter the body during those exposures? • Once in the body, where would the nanomaterials travel, and how would they interact physiologically and chemically with the body’s systems? • Will those interactions be harmless, or could they cause acute or chronic adverse effects? • What are appropriate methods for measuring and controlling exposures to nanometer-diameter particles and nanomaterials in the workplace?
Health Risk Studies These six federal agencies are conducting studies of potential health risks of nanomaterials:- The National Institute of Environmental Health Sciences (including the National Toxicology Program);- The National Institute for Occupational Safety and Health (NIOSH);- The Environmental Protection Agency (EPA);- The Department of Defense;- The Department of Energy (DOE);- The National Science Foundation (NSF) INAIL
Problem areas for regulation of particulates.
PhysicochemicalCharacterizationSize measurement of Nanoparticles Using DLSSize Measurement of Nanoparticles Using Atomic ForceMicroscopyMeasuring the Size of Nanoparticles Using TransmissionElectron MicroscopyDetermination of polymeric NP in Rat Blood with MassSpectrometryQuantification of Free and Chelated Gadolinium Species inNanoemulsion-Based Magnetic Resonance ImagingZeta Potential
In Vitro CharacterizationDetection of Endotoxin Contamination Detectionof Microbial Contamination Detection of Mycoplasma Contamination Targeting Cell Binding/InternalizationAnalysis of Hemolytic Properties of Nanoparticles Analysisof Platelet AggregationAnalysis of Nanoparticle Interaction with Plasma Proteins by2D PAGECoagulation AssayDetection of Nitric Oxide Production by Macrophage
TOXICITYOxidative StressHep G2 Hepatocyte Glutathione AssayHep G2 Hepatocyte Lipid Peroxidation Assay (MDA)Cytotoxicity (necrosis) assay (MTT and LDH ReleaseCytotoxicity (apoptosis) assay (Caspase 3 Activation)Autophagy Assay: Analysis of MAP LC3I to LC3-II Conversionby Western Blot
In Vivo CharacterizationEfficacy Therapeutic Imaging Tissue Distribution Clearance Half-life Systemic exposure (plasma AUC)Single and Repeat-Dose Toxicity