Translocation of ultrafine insoluble iridium particles from lung epithelium to extrapulmonary organs is size dependent but very low

In vitro particulate matter exposure causes direct and lung-mediated indirect effects on cardiomyocyte function

Particulate matter (PM) exposure induces a pathological response from both the lungs and the cardiovascular system. PM is capable of both manifestation into the lung epithelium and entrance into the bloodstream. Therefore, PM has the capacity for both direct and lung-mediated indirect effects on the heart. In the present studies, we exposed isolated rat cardiomyocytes to ultrafine particulate matter (diesel exhaust particles, DEP) and examined their contractile function and calcium handling ability. In another set of experiments, lung epithelial cells (16HBE14o- or Calu-3) were cultured on permeable supports that allowed access to both the basal (serosal) and apical (mucosal) media; the basal media was used to culture cardiomyocytes to model the indirect, lung-mediated effects of PM on the heart. Both the direct and indirect treatments caused a reduction in contractility as evidenced by reduced percent sarcomere shortening and reduced calcium handling ability measured in field-stimulated cardiomyocytes. Treatment of cardiomyocytes with various anti-oxidants before culture with DEP was able to partially prevent the contractile dysfunction. The basal media from lung epithelial cells treated with PM contained several inflammatory cytokines, and we found that monocyte chemotactic protein-1 was a key trigger for cardiomyocyte dysfunction. These results indicate the presence of both direct and indirect effects of PM on cardiomyocyte function in vitro. Future work will focus on elucidating the mechanisms involved in these separate pathways using in vivo models of air pollution exposure.

Zn(II) released from zinc oxide nano/micro particles suppresses vasculogenesis in human endothelial colony-forming cells

Zinc oxide (ZnO) nanoparticles have been widely used in industry, cosmetics, and biomedicine. Recent studies suggested that these nanoparticles could have a major impact on the cardiovascular system. Endothelial progenitor cells (EPCs) contribute to postnatal endothelial repair and regeneration. The present study dissected the effects of ZnO nanoparticles on vasculogenesis using human endothelial colony forming cells (ECFCs), which participate in post-natal vasculogenesis. Two types of ZnO particles were used (nano and micro), in addition to zinc chloride solutions with zinc ion concentrations equal to those in ZnO nanoparticles. Twenty-four-hour exposure induced cytotoxicity in a dose-dependent manner and increased ECFCs apoptosis in all groups. The exposure also reduced the functional capacity of ECFCs on Matrix gel to form tubules, compared with the control cells. These effects were associated with downregulation of expression of vascular endothelial growth factor receptor, VEGFR2 and CXC chemokine receptor, CXCR4. The results suggest that ZnO nanoparticles suppress vasculogenesis from ECFCs through downregulation of the expression of receptors related to vasculogenesis. These effects are based the concentration of released Zn(II).

Biodistribution and Clearance of TiO2 Nanoparticles in Rats after Intravenous Injection

Titanium dioxide (TiO₂) nanoparticles are used in many applications. Due to their small size, easy body penetration and toxicological adverse effects have been suspected. Numerous studies have tried to characterize TiO₂ translocation after oral, dermal or respiratory exposure. In this study, we focused on TiO₂ nanoparticle biodistribution, clearance and toxicological effects after intravenous injection, considering TiO₂ translocation in the blood occurs. Using ICP-OES, transmission electron microscopy, and histological methods, we found TiO₂ accumulation in liver, lungs and spleen. We estimated TiO₂ nanoparticles’ half life in the body to about 10 days. Clinical biomarkers were also quantified for 56 days to identify potential toxicological impact on lungs, blood, liver, spleen and kidneys. Results showed absence of toxicological effects after TiO₂ intravenous injection at concentrations of 7.7 to 9.4 mg/kg.

Inhaled Titanium Dioxide Nanoparticles: A Review of Their Pulmonary Responses with Particular Focus on the Agglomeration State

Nanotechnology represents major scientific and economic issues for the future. TiO 2 is used as a reference nanoparticle (NP) for research and workplace exposure assessments due to its important industrial production. However, to date little consistent information exists about its human health effects. Approximately 50% of all TiO 2in vivo studies targeting the respiratory tract have been by inhalation and these exposures are often in the form of agglomerates rather than as individual NPs. Therefore, the size of the NP agglomerates represents the effective size interacting with the biological material and could thereby influence the NP mechanisms of action. Thus, interpretation of nanotoxicological data without considering the agglomeration state could partly explain the heterogeneous results found in the scientific literature for TiO 2 NPs. The objective of this review is to examine the literature concerning the importance of TiO 2 aerosol characterization in the assessment of pulmonary toxicity in rodents. In this way, this review reveals that the pulmonary responses following inhalation of TiO 2 NPs might not depend solely on the primary NP size, but also on the crystal phase, the NP agglomerate size, its structure and the mass concentration. It also shows that TiO 2 NPs may exert their toxicity mechanisms specifically because of the size of their agglomerates in aerosols, thus supporting the concept that aerosols composed essentially of small (< 100 nm) or large (> 100 nm) NP agglomerates do not seem to follow the same pulmonary toxicity mechanisms.

Comparative cellular toxicity of titanium dioxide nanoparticles on human astrocyte and neuronal cells after acute and prolonged exposure

Although in the last few decades, titanium dioxide nanoparticles (TiO₂NPs) have attracted extensive interest due to their use in wide range of applications, their influences on human health are still quite uncertain and less known. Evidence exists indicating TiO₂NPs ability to enter the brain, thus representing a realistic risk factor for both chronic and accidental exposure with the consequent needs for more detailed investigation on CNS. A rapid and effective in vitro test strategy has been applied to determine the effects of TiO₂NPs anatase isoform, on human glial (D384) and neuronal (SH-SY5Y) cell lines. Toxicity was assessed at different levels: mitochondrial function (by MTT), membrane integrity and cell morphology (by calcein AM/PI staining) after acute exposure (4-24-48 h) at doses from 1.5 to 250 μg/ml as well as growth and cell proliferation (by clonogenic test) after prolonged exposure (7-10 days) at sub-toxic concentrations (from 0.05 to 31 μg/ml). The cytotoxic effects of TiO₂NPs were compared with those caused by TiO₂ bulk counterpart treatment. Acute TiO₂NP exposure produced (i) dose- and time-dependent alterations of the mitochondrial function on D384 and SH-SY5Y cells starting at 31 and 15 μg/ml doses, respectively, after 24h exposure. SH-SY5Y were slightly more sensitive than D384 cells; and (ii) cell membrane damage occurring at 125 μg/ml after 24h exposure in both cerebral cells. Comparatively, the effects of TiO₂ bulk were less pronounced than those induced by nanoparticles in both cerebral cell lines. Prolonged exposure indicated that the proliferative capacity (colony size) was compromised at the extremely low TiO₂NP doses namely 1.5 μg/ml and 0.1 μg/ml for D384 and SH-SY5Y, respectively; cell sensitivity was still higher for SH-SY5Y compared to D384. Colony number decrease (15%) was also evidenced at ≥0.2 μg/ml TiO₂NP dose. Whereas, TiO₂ bulk treatment affected cell morphology only. TiO₂ internalization in SH-SY5Y and D384 cells was appreciated using light microscopy. These findings indicated, that (i) human cerebral SH-SY5Y and D384 cell lines exposed to TiO₂NPs were affected not only after acute but even after prolonged exposure at particularly low doses (≥ 0.1 μg/ml), (ii) these in vitro critical doses were comparable to literature brain Ti levels detected in lab animal intranasally administered with TiO₂NP and associated to neurotoxic effects. In summary, the applied cell-based screening platform seems to provide effective means to initial evaluation of TiO₂NP toxicity on CNS.

Metallic oxide nanoparticle translocation across the human bronchial epithelial barrier

Inhalation is the most frequent route of unintentional exposure to nanoparticles (NPs). Our aim was to quantify the translocation of different metallic NPs across human bronchial epithelial cells and to determine the factors influencing this translocation. Calu-3 cells forming a tight epithelial barrier when grown on a porous membrane in a two compartment chamber were exposed to fluorescently labelled NPs to quantify the NP translocation. NP translocation and uptake by cells were also studied by confocal and transmission electron microscopy. Translocation was characterized according to NP size (16, 50, or 100 nm), surface charge (negative or positive SiO2), composition (SiO2 or TiO2), presence of proteins or phospholipids and in an inflammatory context. Our results showed that NPs can translocate through the Calu-3 monolayer whatever their composition (SiO2 or TiO2), but this translocation was increased for the smallest and negatively charged NPs. Translocation was not associated with an alteration of the integrity of the epithelial monolayer, suggesting a transcytosis of the internalized NPs. By modifying the NP corona, the ability of NPs to cross the epithelial barrier differed depending on their intrinsic properties, making positively charged NPs more prone to translocate. NP translocation can be amplified by using agents known to open tight junctions and to allow paracellular passage. NP translocation was also modulated when mimicking an inflammatory context frequently found in the lungs, altering the epithelial integrity and inducing transient tight junction opening. This in vitro evaluation of NP translocation could be extended to other inhaled NPs to predict their biodistribution.

Suppression of neurite outgrowth of primary cultured hippocampal neurons is involved in impairment of glutamate metabolism and NMDA receptor function caused by nanoparticulate TiO2

Numerous studies have indicated that nano-titanium dioxide (TiO2) can induce neurotoxicity in vitro and in vivo, however, it is unclear whether nano-TiO2 affects neurite outgrowth of hippocampal neurons. In order to investigate the mechanism of neurotoxicity, rat primary cultured hippocampal neurons on the fourth day of culture were exposed to 5, 15, and 30 μg/mL nano-TiO2 for 24 h, and nano-TiO2 internalization, dendritic growth, glutamate metabolism, expression of N-methyl-D-aspartate (NMDA) receptor subunits (NR1, NR2A and NR2B), calcium homeostasis, sodium current (INa) and potassium current (IK) were examined. Our findings demonstrated that nano-TiO2 crossed the membrane into the cytoplasm or nucleus, and significantly suppressed dendritic growth of primary cultured hippocampal neurons in a concentration-dependent manner. Furthermore, nano-TiO2 induced a marked release of glutamate to the extracellular region, decreased glutamine synthetase activity and increased phosphate-activated glutaminase activity, elevated intracellular calcium ([Ca(2+)]i), down-regulated protein expression of NR1, NR2A and NR2B, and increased the amplitudes of the INa and IK. In addition, nano-TiO2 increased nitric oxide and nitrice synthase, attenuated the activities of Ca(2+)-ATPase and Na(+)/K(+)-ATPase, and increased the ADP/ATP ratio in the primary neurons. Taken together, these findings indicate that nano-TiO2 inhibits neurite outgrowth of hippocampal neurons by interfering with glutamate metabolism and impairing NMDA receptor function.

Impact of nanoparticles on human and environment: review of toxicity factors, exposures, control strategies, and future prospects

Nanotechnology has revolutionized the world through introduction of a unique class of materials and consumer products in many arenas. It has led to production of innovative materials and devices. Despite of their unique advantages and applications in domestic and industrial sectors, use of materials with dimensions in nanometers has raised the issue of safety for workers, consumers, and human environment. Because of their small size and other unique characteristics, nanoparticles have ability to harm human and wildlife by interacting through various mechanisms. We have reviewed the characteristics of nanoparticles which form the basis of their toxicity. This paper also reviews possible routes of exposure of nanoparticles to human body. Dermal contact, inhalation, and ingestion have been discussed in detail. As very limited data is available for long-term human exposures, there is a pressing need to develop the methods which can determine short and long-term effects of nanoparticles on human and environment. We also discuss in brief the strategies which can help to control human exposures to toxic nanoparticles. We have outlined the current status of toxicological studies dealing with nanoparticles, accomplishments, weaknesses, and future challenges.

Anatase titanium dioxide nanoparticles in mice: evidence for induced structural and functional sperm defects after short-, but not long-, term exposure

Titanium dioxide (TiO 2 ) nanoparticles (TNPs) are widely used commercially and exist in a variety of products. To determine if anatase TNPs (ATNPs) in doses smaller than previously used reach the scrotum after entry in the body at a distant location and induce sperm defects, 100% ATNP (2.5 or 5 mg kg-1 body weight) was administered intraperitoneally to adult males for three consecutive days, followed by sacrifice 1, 2, 3, or 5 weeks later (long-) or 24, 48 or 120 h (short-term exposure). Transmission electron microscopy revealed the presence of ANTP in scrotal adipose tissues collected 120 h postinjection when cytokine evaluation showed an inflammatory response in epididymal tissues and fluid. At 120 h and up to 3 weeks postinjection, testicular histology revealed enlarged interstitial spaces. Significantly increased numbers of terminal deoxyribonucleotidyl transferase-mediated dUTP nick-end labeling-positive (apoptotic) germ (P = 0.002) and interstitial space cells (P = 0.04) were detected in treated males. Caudal epididymal sperm from the short-term, but not a long-term, arm showed significantly (P < 0.001) increased frequencies of flagellar abnormalities, excess residual cytoplasm (ERC), and unreacted acrosomes in treated versus controls (dose-response relationship). A novel correlation between ERC and unreacted acrosomes was uncovered. At 120 h, there were significant decreases in hyperactivated motility (P < 0.001) and mitochondrial membrane potential (P < 0.05), and increased reactive oxygen species levels (P < 0.00001) in treated versus control sperm. These results indicate that at 4-8 days postinjection, ANTP induce structural and functional sperm defects associated with infertility, and DNA damage via oxidative stress. Sperm defects were transient as they were not detected 10 days to 5 weeks postinjection.

Maternal exposure to fine particulate matter (PM2.5) and pregnancy outcomes: a meta-analysis

A growing body of evidence has investigated the association between maternal exposure to PM2.5 (particulate matter with aerodynamic diameter 2.5 μm) during pregnancy and adverse pregnancy outcomes. However, the results of those studies are not consistent. To synthetically quantify the relationship between maternal exposure to PM2.5 during pregnancy and pregnancy outcomes (the change in birth weight, low birth weight (LBW), preterm birth (PTB), small for gestational age (SGA), and stillbirth), a meta-analysis of 25 published observational epidemiological studies that met our selection criteria was conducted. Results suggested a 10 μg/m(3) increase in PM2.5 was positively associated with LBW (odds ratio (OR) = 1.05; 95 % confidence interval (CI), 1.02-1.07), PTB (OR = 1.10; 95 % CI, 1.03-1.18), and SGA (OR = 1.15; 95 % CI, 1.10-1.20) based on entire pregnancy exposure, and pooled estimate of decrease in birth weight was 14.58 g (95 % CI, 9.86-19.31); however, there was no evidence of a statistically significant effect of per 10 μg/m(3) increase in PM2.5 exposure on the risk of stillbirth (OR = 1.18; 95 % CI, 0.69-2.04). With respect to three different gestation periods, no significant risks were found in PTB, stillbirth, and the first trimester on the change of birth weight with a 10 μg/m(3) increase in PM2.5. In this study, a comprehensive quantitative analysis of the results show that PM2.5 can increase the risk of LBW, PTB, and SGA; pregnant women need to take effective measures to reduce PM2.5 exposure.

Characterization of airborne particles generated from metal active gas welding process

This study is focused on the characterization of particles emitted in the metal active gas welding of carbon steel using mixture of Ar + CO2, and intends to analyze which are the main process parameters that influence the emission itself. It was found that the amount of emitted particles (measured by particle number and alveolar deposited surface area) are clearly dependent on the distance to the welding front and also on the main welding parameters, namely the current intensity and heat input in the welding process. The emission of airborne fine particles seems to increase with the current intensity as fume-formation rate does. When comparing the tested gas mixtures, higher emissions are observed for more oxidant mixtures, that is, mixtures with higher CO2 content, which result in higher arc stability. These mixtures originate higher concentrations of fine particles (as measured by number of particles by cm(3) of air) and higher values of alveolar deposited surface area of particles, thus resulting in a more severe worker's exposure.

Advances in Inhalation Dosimetry Models and Methods for Occupational Risk Assessment and Exposure Limit Derivation

The purpose of this article is to provide an overview and practical guide to occupational health professionals concerning the derivation and use of dose estimates in risk assessment for development of occupational exposure limits (OELs) for inhaled substances. Dosimetry is the study and practice of measuring or estimating the internal dose of a substance in individuals or a population. Dosimetry thus provides an essential link to understanding the relationship between an external exposure and a biological response. Use of dosimetry principles and tools can improve the accuracy of risk assessment, and reduce the uncertainty, by providing reliable estimates of the internal dose at the target tissue. This is accomplished through specific measurement data or predictive models, when available, or the use of basic dosimetry principles for broad classes of materials. Accurate dose estimation is essential not only for dose-response assessment, but also for interspecies extrapolation and for risk characterization at given exposures. Inhalation dosimetry is the focus of this paper since it is a major route of exposure in the workplace. Practical examples of dose estimation and OEL derivation are provided for inhaled gases and particulates.

Oxidative and pro-inflammatory effects of cobalt and titanium oxide nanoparticles on aortic and venous endothelial cells

Ultra-fine particles have recently been included among the risk factors for the development of endothelium inflammation and atherosclerosis, and cobalt (CoNPs) and titanium oxide nanoparticles (TiNPs) have attracted attention because of their wide range of applications. We investigated their toxicity profiles in two primary endothelial cell lines derived from human aorta (HAECs) and human umbilical vein (HUVECs) by comparing cell viability, oxidative stress, the expression of adhesion molecules and the release of chemokines during NP exposure. Both NPs were very rapidly internalised, and significantly increased adhesion molecule (ICAM-1, VCAM-1, E-selectin) mRNA and protein levels and the release of monocyte chemoattractant protein-1 (MCP-1) and interleukin 8 (IL-8). However, unlike the TiNPs, the CoNPs also induced time- and concentration-dependent metabolic impairment and oxidative stress without any evident signs of cell death or the induction of apoptosis. There were differences between the HAECs and HUVECs in terms of the extent of oxidative stress-related enzyme and vascular adhesion molecule expression, ROS production, and pro-inflammatory cytokine release despite the similar rate of NP internalisation, thus indicating endothelium heterogeneity in response to exogenous stimuli. Our data indicate that NPs can induce endothelial inflammatory responses via various pathways not involving only oxidative stress.

A 90-day study of subchronic oral toxicity of 20 nm, negatively charged zinc oxide nanoparticles in Sprague Dawley rats

PURPOSE

The widespread use of nanoparticles (NPs) in industrial and biomedical applications has prompted growing concern regarding their potential toxicity and impact on human health. This study therefore investigated the subchronic, systemic oral toxicity and no-observed-adverse-effect level (NOAEL) of 20 nm, negatively charged zinc oxide (ZnO(SM20(-))) NPs in Sprague Dawley rats for 90 days.

METHODS

The high-dose NP level was set at 500 mg/kg of bodyweight, and the mid- and low-dose levels were set at 250 and 125 mg/kg, respectively. The rats were observed during a 14-day recovery period after the last NP administration for the persistence or reduction of any adverse effects. Toxicokinetic and distribution studies were also conducted to determine the systemic distribution of the NPs.

RESULTS

No rats died during the test period. However, ZnO(SM20(-)) NPs (500 mg/kg) induced changes in the levels of anemia-related factors, prompted acinar cell apoptosis and ductular hyperplasia, stimulated periductular lymphoid cell infiltration and excessive salivation, and increased the numbers of regenerative acinar cells in the pancreas. In addition, stomach lesions were seen at 125, 250, and 500 mg/kg, and retinal atrophy was observed at 250 and 500 mg/kg. The Zn concentration was dose-dependently increased in the liver, kidney, intestines, and plasma, but not in other organs investigated.

CONCLUSION

A ZnO(SM20(-)) NP NOAEL could not be established from the current results, but the lowest-observed-adverse-effect level was 125 mg/kg. Furthermore, the NPs were associated with a number of undesirable systemic actions. Thus, their use in humans must be approached with caution.

Pulmonary toxicity of nanomaterials: a critical comparison of published in vitro assays and in vivo inhalation or instillation studies

To date, guidance on how to incorporate in vitro assays into integrated approaches for testing and assessment of nanomaterials is unavailable. In addressing this shortage, this review compares data from in vitro studies to results from in vivo inhalation or intratracheal instillation studies. Globular nanomaterials (ion-shedding silver and zinc oxide, poorly soluble titanium dioxide and cerium dioxide, and partly soluble amorphous silicon dioxide) and nanomaterials with higher aspect ratios (multiwalled carbon nanotubes) were assessed focusing on the Organisation for Economic Co-Operation and Development (OECD) reference nanomaterials for these substances. If in vitro assays are performed with dosages that reflect effective in vivo dosages, the mechanisms of nanomaterial toxicity can be assessed. In early tiers of integrated approaches for testing and assessment, knowledge on mechanisms of toxicity serves to group nanomaterials thereby reducing the need for animal testing.

Nanosafety research--are we on the right track?

The number of studies that have been published on the topic of nanosafety speaks for itself. We have seen an almost exponential rise over the past 15 years or so in the number of articles on nanotoxicology. Although only a couple of hundred papers had appeared on the topic of "Nanomaterials: environmental and health effects" before 2000, this number has exploded to over 10 000 since 2001. Most of these studies, however, do not offer any kind of clear statement on the safety of nanomaterials. On the contrary, most of them are either self-contradictory or arrive at completely erroneous conclusions. Three years ago in this Journal we underscored the deficiencies in the way these studies were designed and pointed out the sources of error in the methods used. Now, on the basis of a comprehensive review of the literature and with the help of selected toxicological end points, we attempt to indicate where the significant weaknesses of these studies lie and what we must improve in the future.

Persistence of silver nanoparticles in the rat lung: Influence of dose, size, and chemical composition

Increasing silver nanoparticle (AgNP) use in sprays, consumer products, and medical devices has raised concerns about potential health effects. While previous studies have investigated AgNPs, most were limited to a single particle size or surface coating. In this study, we investigated the effect of size, surface coating, and dose on the persistence of silver in the lung following exposure to AgNP. Adult male rats were intratracheally instilled with four different AgNPs: 20 or 110 nm in size and coated with either citrate or polyvinylpyrrolidone (PVP) at 0.5 or 1.0 mg/kg doses. Silver retention was assessed in the lung at 1, 7, and 21 d post exposure. ICP-MS quantification demonstrated that citrate-coated AgNPs persisted in the lung to 21 d with retention greater than 90%, while PVP-coated AgNP had less than 30% retention. Localization of silver in lung tissue at 1 d post exposure demonstrated decreased silver in proximal airways exposed to 110 nm particles compared with 20 nm AgNPs. In terminal bronchioles 1 d post exposure, silver was localized to surface epithelium but was more prominent in the basement membrane at 7 d. Silver positive macrophages in bronchoalveolar lavage fluid decreased more quickly after exposure to particles coated with PVP. We conclude that PVP-coated AgNPs had less retention in the lung tissue over time and larger particles were more rapidly cleared from large airways than smaller particles. The 20 nm citrate particles showed the greatest effect, increasing lung macrophages even 21 d after exposure, and resulted in the greatest silver retention in lung tissue.

Size dependent translocation and fetal accumulation of gold nanoparticles from maternal blood in the rat

BACKGROUND

There is evidence that nanoparticles (NP) cross epithelial and endothelial body barriers. We hypothesized that gold (Au) NP, once in the blood circulation of pregnant rats, will cross the placental barrier during pregnancy size-dependently and accumulate in the fetal organism by 1. transcellular transport across the hemochorial placenta, 2. transcellular transport across amniotic membranes 3. transport through ~20 nm wide transtrophoblastic channels in a size dependent manner. The three AuNP sizes used to test this hypothesis are either well below, or of similar size or well above the diameters of the transtrophoblastic channels.

METHODS

We intravenously injected monodisperse, negatively charged, radio-labelled 1.4 nm, 18 nm and 80 nm ¹⁹⁸AuNP at a mass dose of 5, 3 and 27 μg/rat, respectively, into pregnant rats on day 18 of gestation and in non-pregnant control rats and studied the biodistribution in a quantitative manner based on the radio-analysis of the stably labelled ¹⁹⁸AuNP after 24 hours.

RESULTS

We observed significant biokinetic differences between pregnant and non-pregnant rats. AuNP fractions in the uterus of pregnant rats were at least one order of magnitude higher for each particle size roughly proportional to the enlarged size and weight of the pregnant uterus. All three sizes of ¹⁹⁸AuNP were found in the placentas and amniotic fluids with 1.4 nm AuNP fractions being two orders of magnitude higher than those of the larger AuNP on a mass base. In the fetuses, only fractions of 0.0006 (30 ng) and 0.00004 (0.1 ng) of 1.4 nm and 18 nm AuNP, respectively, were detected, but no 80 nm AuNP (<0.000004 (<0.1 ng)). These data show that no AuNP entered the fetuses from amniotic fluids within 24 hours but indicate that AuNP translocation occurs across the placental tissues either through transtrophoblastic channels and/or via transcellular processes.

CONCLUSION

Our data suggest that the translocation of AuNP from maternal blood into the fetus is NP-size dependent which is due to mechanisms involving (1) transport through transtrophoblastic channels - also present in the human placenta - and/or (2) endocytotic and diffusive processes across the placental barrier.

Early life exposure to air pollution induces adult cardiac dysfunction

Exposure to ambient air pollution contributes to the progression of cardiovascular disease, particularly in susceptible populations. The objective of the present study was to determine whether early life exposure to air pollution causes persistent cardiovascular consequences measured at adulthood. Pregnant FVB mice were exposed to filtered (FA) or concentrated ambient particulate matter (PM2.5) during gestation and nursing. Mice were exposed to PM2.5 at an average concentration of 51.69 μg/m(3) from the Columbus, OH region for 6 h/day, 7 days/wk in utero until weaning at 3 wk of age. Birth weight was reduced in PM2.5 pups compared with FA (1.36 ± 0.12 g FA, n = 42 mice; 1.30 ± 0.15 g PM2.5, n = 67 P = 0.012). At adulthood, mice exposed to perinatal PM2.5 had reduced left ventricular fractional shortening compared with FA-exposed mice (43.6 ± 2.1% FA, 33.2 ± 1.6% PM2.5, P = 0.001) with greater left ventricular end systolic diameter. Pressure-volume loops showed reduced ejection fraction (79.1 ± 3.5% FA, 35.5 ± 9.5% PM2.5, P = 0.005), increased end-systolic volume (10.4 ± 2.5 μl FA, 39.5 ± 3.8 μl PM2.5, P = 0.001), and reduced dP/dt maximum (11,605 ± 200 μl/s FA, 9,569 ± 800 μl/s PM2.5, P = 0.05) and minimum (-9,203 ± 235 μl/s FA, -7,045 ± 189 μl/s PM2.5, P = 0.0005) in PM2.5-exposed mice. Isolated cardiomyocytes from the hearts of PM2.5-exposed mice had reduced peak shortening (%PS, 8.53 ± 2.82% FA, 6.82 ± 2.04% PM2.5, P = 0.003), slower calcium reuptake (τ, 0.22 ± 0.09 s FA, 0.26 ± 0.07 s PM2.5, P = 0.048), and reduced response to β-adrenergic stimulation compared with cardiomyocytes isolated from mice that were exposed to FA. Histological analyses revealed greater picro-sirius red-positive-stained areas in the PM2.5 vs. FA group, indicative of increased collagen deposition. We concluded that these data demonstrate the detrimental role of early life exposure to ambient particulate air pollution in programming of adult cardiovascular diseases and the potential for PM2.5 to induce persistent cardiac dysfunction at adulthood.

Physicochemical properties of nanomaterials: implication in associated toxic manifestations

Nanotechnology has emerged as one of the leading fields of the science having tremendous application in diverse disciplines. As nanomaterials are increasingly becoming part of everyday consumer products, it is imperative to assess their impact on living organisms and on the environment. Physicochemical characteristics of nanoparticles and engineered nanomaterials including size, shape, chemical composition, physiochemical stability, crystal structure, surface area, surface energy, and surface roughness generally influence the toxic manifestations of these nanomaterials. This compels the research fraternity to evaluate the role of these properties in determining associated toxicity issues. Reckoning with this fact, in this paper, issues pertaining to the physicochemical properties of nanomaterials as it relates to the toxicity of the nanomaterials are discussed.

Mechanisms of TiO2 nanoparticle-induced neuronal apoptosis in rat primary cultured hippocampal neurons

Exposure to titanium dioxide nanoparticles (TiO2 NPs) has been demonstrated to decrease learning and memory of animals. However, whether the impacts of these NPs on the recognition function are involved in hippocamal neuron damages is poorly understood. In this study, primary cultured hippocampal neurons from one-day-old fetal Sprague-Dawley rats were exposed to 5, 15, or 30 µg/mL TiO2 NPs for 24 h, we investigated cell viability, ultrastructure, and mitochondrial membrane potential (MMP), calcium homeostasis, oxidative stress, antioxidant capacity, apoptotic signaling pathway associated with the primary cultured hippocamal neuron apoptosis. Our findings showed that TiO2 NP treatment resulted in reduction of cell viability, promoted lactate dehydrogenase release, apoptosis, and increased neuron apoptotic rate in a dose-dependent manner. Furthermore, TiO2 NPs led to [Ca(2+)]i elevation, and MMP reduction, up-regulated protein expression of cytochrome c, Bax, caspase-3, glucose-regulated protein 78, C/EBP homologous protein and caspase-12, and down-regulated bcl-2 expression in the primary cultured hippocampal neurons. These findings suggested that hippocampal neuron apoptosis caused by TiO2 NPs may be associated with mitochondria-mediated signal pathway and endoplasmic reticulum-mediated signal pathway.

Modulatory effect of nano TiO₂on Pb in Hoplias malabaricus trophically exposed

This study investigated the hepatic and neural effects of TiO₂ nanoparticle and Pb in Hoplias malabaricus trophically exposed. The alanine transaminase activity was altered at the high dose of exposed group to Pb and at the lowest doses of co-exposed groups. It may reflect the hepatic effects of TiO₂ on Pb toxicity, but the aspatate transaminase activity was not altered. The decreased injury index observed at the highest dose of co-exposed group compared to TiO₂ may be related to the increased energy demand and can explain the more pronounced toxic effects observed in this group. The liver authomethallography revealed the metals presence at high dose groups. Serotonin concentration increased at the Pb lowest dose and at the highest dose of co-exposed group compare to control. Most importantly, when associated the contaminants were able to interact and altered some biomarkers. However, further studies, about action mechanisms of this co-exposure are needed.

Environmental risk factors and amyotrophic lateral sclerosis (ALS): a case-control study of ALS in Michigan

An interim report of a case-control study was conducted to explore the role of environmental factors in the development of amyotrophic lateral sclerosis (ALS). Sixty-six cases and 66 age- and gender-matched controls were recruited. Detailed information regarding residence history, occupational history, smoking, physical activity, and other factors was obtained using questionnaires. The association of ALS with potential risk factors, including smoking, physical activity and chemical exposure, was investigated using conditional logistic regression models. As compared to controls, a greater number of our randomly selected ALS patients reported exposure to fertilizers to treat private yards and gardens and occupational exposure to pesticides in the last 30 years than our randomly selected control cases. Smoking, occupational exposures to metals, dust/fibers/fumes/gas and radiation, and physical activity were not associated with ALS when comparing the randomly selected ALS patients to the control subjects. To further explore and confirm results, exposures over several time frames, including 0-10 and 10-30 years earlier, were considered, and analyses were stratified by age and gender. Pesticide and fertilizer exposure were both significantly associated with ALS in the randomly selected ALS patients. While study results need to be interpreted cautiously given the small sample size and the lack of direct exposure measures, these results suggest that environmental and particularly residential exposure factors warrant close attention in studies examining risk factors of ALS.

Systemic and vascular effects of circulating diesel exhaust particulate matter

OBJECTIVE

Numerous studies have found an association between transiently increased particulate matter air pollution and acute adverse cardiovascular health effects; however, the mechanisms underlying these effects are not clear. Translocation of ultra-fine ambient particulate matter has been proposed to play a key role in these acute side effects. This study was designed to determine the contribution of circulating (translocated) diesel exhaust particles (DEPs) to the systemic and vascular effects.

METHODS

C57 mice (10-week) received intravenous DEPs via tail vein injection. Following 1-h post-injection, inflammatory cytokines (IL-1β, IL-6 and TNF-α), peripheral blood cell counts, band cell counts, aortic endothelial function and vascular constriction were assessed. Thoracic aortae were isolated, and endothelial function was examined by measuring acetylcholine (ACh) and sodium nitroprusside (SNP)-stimulated vascular relaxation using a wire myograph. In addition, phenylephrine (PE)-stimulated vasoconstriction was also measured. The amount of DEPs deposited and trapped in tissues (the spleen, liver, lungs and heart) were quantified.

RESULTS

Acute systemic DEP exposure caused a significant increase in TNF-α, peripheral neutrophil and band cell counts. ACh and SNP-induced relaxation were not affected by acute systemic DEP exposure, neither was PE-stimulated constriction. There was a significantly increased DEP deposition in the spleen as well as in the liver. No significantly increased DEPs were detected in the lung and heart.

CONCLUSION

Here we show that circulating DEPs induce a systemic response characterized by increased TNF-α, peripheral granulocytes, but does not impact endothelial function. Our study also suggests that circulating particles are rapidly removed from the circulation and predominantly sequestered in the spleen and liver.

Respirable nanocarriers as a promising strategy for antitubercular drug delivery

Tuberculosis is considered a fatal respiratory infectious disease that represents a global threat, which must be faced. Despite the availability of oral conventional anti-tuberculosis therapy, the disease is characterized by high progression. The leading causes are poor patient compliance and failure to adhere to the drug regimen primarily due to systemic toxicity. In this context, inhalation therapy as a non-invasive route of administration is capable of increasing local drug concentrations in lung tissues, the primary infection side, by passive targeting as well as reducing the risk of systemic toxicity and hence improving the patient compliance. Nanotechnology represents a promising strategy in the development of inhaled drug delivery systems. Nanocarriers can improve the drug effectiveness and decrease the expected side effects as consequences of their ability to target the drug to the infected area as well as sustain its release in a prolonged manner. The current review summarizes the state-of-the-art in the development of inhaled nanotechnological carriers confined currently available anti-tuberculosis drugs (anti TB) for local and targeting drug delivery specifically, polymeric nanoparticles, solid lipid nanoparticles, nanoliposomes and nanomicelles. Moreover, complexes and ion pairs are also reported. The impact and progress of nanotechnology on the therapeutic effectiveness and patient adherence to anti TB regimen are addressed.

Nanoparticle mass transfer from lung airways to systemic regions--Part II: Multi-compartmental modeling

This is the second article of a two-part paper, combining high-resolution computer simulation results of inhaled nanoparticle deposition in a human airway model (Kolanjiyil and Kleinstreuer, 2013, "Nanoparticle Mass Transfer From Lung Airways to Systemic Regions--Part I: Whole-Lung Aerosol Dynamics," ASME J. Biomech. Eng., 135(12), p. 121003) with a new multicompartmental model for insoluble nanoparticle barrier mass transfer into systemic regions. Specifically, it allows for the prediction of temporal nanoparticle accumulation in the blood and lymphatic systems and in organs. The multicompartmental model parameters were determined from experimental retention and clearance data in rat lungs and then the validated model was applied to humans based on pharmacokinetic cross-species extrapolation. This hybrid simulator is a computationally efficient tool to predict the nanoparticle kinetics in the human body. The study provides critical insight into nanomaterial deposition and distribution from the lungs to systemic regions. The quantitative results are useful in diverse fields such as toxicology for exposure-risk analysis of ubiquitous nanomaterial and pharmacology for nanodrug development and targeting.

Biokinetics of nanoparticles and susceptibility to particulate exposure in a murine model of cystic fibrosis

BACKGROUND

Persons with cystic fibrosis (CF) are at-risk for health effects from ambient air pollution but little is known about the interaction of nanoparticles (NP) with CF lungs. Here we study the distribution of inhaled NP in a murine CF model and aim to reveal mechanisms contributing to adverse effects of inhaled particles in susceptible populations.

METHODS

Chloride channel defective CftrTgH (neoim) Hgu mice were used to analyze lung function, lung distribution and whole body biokinetics of inhaled NP, and inflammatory responses after intratracheal administration of NP. Distribution of 20-nm titanium dioxide NP in lungs was assessed on ultrathin sections immediately and 24 h after a one-hour NP inhalation. NP biokinetics was deduced from total and regional lung deposition and from whole body translocation of inhaled 30-nm iridium NP within 24 h after aerosol inhalation. Inflammatory responses were assessed within 7 days after carbon NP instillation.

RESULTS

Cftr mutant females had moderately reduced lung compliance and slightly increased airway resistance compared to wild type mice. We found no genotype dependent differences in total, regional and head deposition or in secondary-organ translocation of inhaled iridium NP. Titanium dioxide inhalation resulted in higher NP uptake by alveolar epithelial cells in Cftr mutants. Instillation of carbon NP induced a comparable acute and transient inflammatory response in both genotypes. The twofold increase of bronchoalveolar lavage (BAL) neutrophils in Cftr mutant compared to wild type mice at day 3 but not at days 1 and 7, indicated an impaired capacity in inflammation resolution in Cftr mutants. Concomitant to the delayed decline of neutrophils, BAL granulocyte-colony stimulating factor was augmented in Cftr mutant mice. Anti-inflammatory 15-hydroxyeicosatetraenoic acid was generally significantly lower in BAL of Cftr mutant than in wild type mice.

CONCLUSIONS

Despite lacking alterations in lung deposition and biokinetics of inhaled NP, and absence of significant differences in lung function, higher uptake of NP by alveolar epithelial cells and prolonged, acute inflammatory responses to NP exposure indicate a moderately increased susceptibility of lungs to adverse effects of inhaled NP in Cftr mutant mice and provides potential mechanisms for the increased susceptibility of CF patients to air pollution.

Zinc oxide nanoparticles induce migration and adhesion of monocytes to endothelial cells and accelerate foam cell formation

Metal oxide nanoparticles are widely used in industry, cosmetics, and biomedicine. However, the effects of exposure to these nanoparticles on the cardiovascular system remain unknown. The present study investigated the effects of nanosized TiO2 and ZnO particles on the migration and adhesion of monocytes, which are essential processes in atherosclerogenesis, using an in vitro set-up of human umbilical vein endothelial cells (HUVECs) and human monocytic leukemia cells (THP-1). We also examined the effects of exposure to nanosized metal oxide particles on macrophage cholesterol uptake and foam cell formation. The 16-hour exposure to ZnO particles increased the level of monocyte chemotactic protein-1 (MCP-1) and induced the migration of THP-1 monocyte mediated by increased MCP-1. Exposure to ZnO particles also induced adhesion of THP-1 cells to HUVECs. Moreover, exposure to ZnO particles, but not TiO2 particles, upregulated the expression of membrane scavenger receptors of modified LDL and increased cholesterol uptake in THP-1 monocytes/macrophages. In the present study, we found that exposure to ZnO particles increased macrophage cholesterol uptake, which was mediated by an upregulation of membrane scavenger receptors of modified LDL. These results suggest that nanosized ZnO particles could potentially enhance atherosclerogenesis and accelerate foam cell formation.

Physicochemical characteristics of nanomaterials that affect pulmonary inflammation

The increasing manufacture and use of products based on nanotechnology raises concerns for both workers and consumers. Various studies report induction of pulmonary inflammation after inhalation exposure to nanoparticles, which can vary in aspects such as size, shape, charge, crystallinity, chemical composition, and dissolution rate. Each of these aspects can affect their toxicity, although it is largely unknown to what extent. The aim of the current review is to analyse published data on inhalation of nanoparticles to identify and evaluate the contribution of their physicochemical characteristics to the onset and development of pulmonary inflammation. Many physicochemical characteristics of nanoparticles affect their lung deposition, clearance, and pulmonary response that, in combination, ultimately determine whether pulmonary inflammation will occur and to what extent. Lung deposition is mainly determined by the physical properties of the aerosol (size, density, shape, hygroscopicity) in relation to airflow and the anatomy of the respiratory system, whereas clearance and translocation of nanoparticles are mainly determined by their geometry and surface characteristics. Besides size and chemical composition, other physicochemical characteristics influence the induction of pulmonary inflammation after inhalation. As some nanoparticles dissolve, they can release toxic ions that can damage the lung tissue, making dissolution rate an important characteristic that affects lung inflammation. Fibre-shaped materials are more toxic to the lungs compared to spherical shaped nanoparticles of the same chemical composition. In general, cationic nanoparticles are more cytotoxic than neutral or anionic nanoparticles. Finally, surface reactivity correlates well with observed pulmonary inflammation. With all these characteristics affecting different stages of the events leading to pulmonary inflammation, no unifying dose metric could be identified to describe pulmonary inflammation for all nanomaterials, although surface reactivity might be a useful measure. To determine the extent to which the various characteristics influence the induction of pulmonary inflammation, the effect of these characteristics on lung deposition, clearance, and pulmonary response should be systematically evaluated. The results can then be used to facilitate risk assessment by categorizing nanoparticles according to their characteristics.

Effects of maternal exposure to ultrafine carbon black on brain perivascular macrophages and surrounding astrocytes in offspring mice

Perivascular macrophages (PVMs) constitute a subpopulation of resident macrophages in the central nervous system (CNS). They are located at the blood-brain barrier and can contribute to maintenance of brain functions in both health and disease conditions. PVMs have been shown to respond to particle substances administered during the prenatal period, which may alter their phenotype over a long period. We aimed to investigate the effects of maternal exposure to ultrafine carbon black (UfCB) on PVMs and astrocytes close to the blood vessels in offspring mice. Pregnant mice were exposed to UfCB suspension by intranasal instillation on gestational days 5 and 9. Brains were collected from their offspring at 6 and 12 weeks after birth. PVM and astrocyte phenotypes were examined by Periodic Acid Schiff (PAS) staining, transmission electron microscopy and PAS-glial fibrillary acidic protein (GFAP) double staining. PVM granules were found to be enlarged and the number of PAS-positive PVMs was decreased in UfCB-exposed offspring. These results suggested that in offspring, “normal” PVMs decreased in a wide area of the CNS through maternal UfCB exposure. The increase in astrocytic GFAP expression level was closely related to the enlargement of granules in the attached PVMs in offspring. Honeycomb-like structures in some PVM granules and swelling of astrocytic end-foot were observed under electron microscopy in the UfCB group. The phenotypic changes in PVMs and astrocytes indicate that maternal UfCB exposure may result in changes to brain blood vessels and be associated with increased risk of dysfunction and disorder in the offspring brain.

TiO2 nanoparticles induced hippocampal neuroinflammation in mice

Titanium dioxide nanoparticles (TiO2 NPs) have been used in various medical and industrial areas. However, the impacts of these nanoparticles on neuroinflammation in the brain are poorly understood. In this study, mice were exposed to 2.5, 5, or 10 mg/kg body weight TiO2 NPs for 90 consecutive days, and the TLRs/TNF-α/NF-κB signaling pathway associated with the hippocampal neuroinflammation was investigated. Our findings showed titanium accumulation in the hippocampus, neuroinflammation and impairment of spatial memory in mice following exposure to TiO2 NPs. Furthermore, TiO2 NPs significantly activated the expression of Toll-like receptors (TLR2, TLR4), tumor necrosis factor-α, nucleic IκB kinase, NF-κB-inducible kinase, nucleic factor-κB, NF-κB2(p52), RelA(p65), and significantly suppressed the expression of IκB and interleukin-2. These findings suggest that neuroinflammation may be involved in TiO2 NP-induced alterations of cytokine expression in mouse hippocampus. Therefore, more attention should be focused on the application of TiO2 NPs in the food industry and their long-term exposure effects, especially in the human central nervous system.

Toxicological assessment of inhaled nanoparticles: role of in vivo, ex vivo, in vitro, and in silico studies

The alveolar epithelium of the lung is by far the most permeable epithelial barrier of the human body. The risk for adverse effects by inhaled nanoparticles (NPs) depends on their hazard (negative action on cells and organism) and on exposure (concentration in the inhaled air and pattern of deposition in the lung). With the development of advanced in vitro models, not only in vivo, but also cellular studies can be used for toxicological testing. Advanced in vitro studies use combinations of cells cultured in the air-liquid interface. These cultures are useful for particle uptake and mechanistic studies. Whole-body, nose-only, and lung-only exposures of animals could help to determine retention of NPs in the body. Both approaches also have their limitations; cellular studies cannot mimic the entire organism and data obtained by inhalation exposure of rodents have limitations due to differences in the respiratory system from that of humans. Simulation programs for lung deposition in humans could help to determine the relevance of the biological findings. Combination of biological data generated in different biological models and in silico modeling appears suitable for a realistic estimation of potential risks by inhalation exposure to NPs.

A bibliometric analysis of research on the risk of engineering nanomaterials during 1999-2012

A bibliometric analysis based on the Science Citation Index Expanded (SCI-Expanded) from the Web of Science was carried out to provide insights into research activities and tendencies of the global risk of engineering nanomaterials (ENMs) from 1999 to 2012. The number of publications per year has increased steadily since approximately 2006. The USA produced 41.9% of all pertinent articles followed by China with 14.8% and UK with 9.1%. Environmental Science & Technology, Toxicology, and Journal of Nanoparticle Research were the three most common journals in this field. A synthesized analysis by co-citation and words from author keywords provided the clues to discover the current research emphases. The mainstream research related to risk of ENMs was toxicological effects and ecological risk. Toxicity effect strongly promoted the development of related research in the past 14 years. Research on environmental behavior and ecological risk of ENMs is the fast growing field.

Application of a high-efficiency cabin air filter for simultaneous mitigation of ultrafine particle and carbon dioxide exposures inside passenger vehicles

Modern passenger vehicles are commonly equipped with cabin air filters but their filtration efficiency for ultrafine particle (UFP) is rather low. Although setting the vehicle ventilation system to recirculation (RC) mode can reduce in-cabin UFPs by ∼ 90%, passenger-exhaled carbon dioxide (CO2) can quickly accumulate inside the cabin. Using outdoor air (OA) mode instead can provide sufficient air exchange to prevent CO2 buildup, but in-cabin UFP concentrations would increase. To overcome this dilemma, we developed a simultaneous mitigation method for UFP and CO2 using high-efficiency cabin air (HECA) filtration in OA mode. Concentrations of UFP and other air pollutants were simultaneously monitored in and out of 12 different vehicles under 3 driving conditions: stationary, on local roadways, and on freeways. Under each experimental condition, data were collected with no filter, in-use original equipment manufacturer (OEM) filter, and two types of HECA filters. The HECA filters offered an average in-cabin UFP reduction of 93%, much higher than the OEM filters (∼ 50% on average). Throughout the measurements, the in-cabin CO2 concentration remained in the range of 620-930 ppm, significantly lower than the typical level of 2500-4000 ppm observed in the RC mode.

New approach to investigate the cytotoxicity of nanomaterials using single cell mechanics

Current in vitro methods to assess nanomaterial cytotoxicity involve various assays to monitor specific cellular dysfunction, such as metabolic imbalance or inflammation. Although high throughput, fast, and animal-free, these in vitro methods suffer from unreliability and lack of relevance to in vivo situations. New approaches, especially with the potential to reliably relate to in vivo studies directly, are in critical need. This work introduces a new approach, single cell mechanics, derived from atomic force microscopy-based single cell compression. The single cell based approach is intrinsically advantageous in terms of being able to directly correlate to in vivo investigations. Its reliability and potential to measure cytotoxicity is evaluated using known systems: zinc oxide (ZnO) and silicon dioxide (SiO2) nanoparticles (NP) on human aortic endothelial cells (HAECs). This investigation clearly indicates the reliability of single cell compression. For example, ZnO NPs cause significant changes in force vs relative deformation profiles, whereas SiO2 NPs do not. New insights into NPs-cell interactions pertaining to cytotoxicity are also revealed from this single cell mechanics approach, in addition to a qualitative cytotoxicity conclusion. The advantages and disadvantages of this approach are also compared with conventional cytotoxicity assays.

Role of size of drug delivery carriers for pulmonary and intravenous administration with emphasis on cancer therapeutics and lung-targeted drug delivery

The design of a drug delivery system and the fabrication of efficient, successful, and targeted drug carriers are two separate issues that require slightly different design parameters.

Endocytosis of environmental and engineered micro- and nanosized particles

There are many studies with cells to find out how particles interact with them. In contrast to micronsized particles, which are actively taken up by phagocytosis or macropinocytosis, nanosized particles may be taken up by cells through different endocytic pathways or by another, yet to be defined mechanism. There is increasing evidence that it is the nanosized particles, which are a particular risk because of their high content of organic chemicals and their pro-oxidative potential due to the high surface-to-volume ratio of the particles as compared to the bulk material. It is the goal of this article to create an understanding for the interaction of particles with biological systems, with particular consideration of the interaction of nanoparticles (NPs) with lung cells. One is attempting to understand, how NPs interact with cellular membranes, as it is hardly known, how they are taken up by cells, how they are trafficking in cells, and how they interact with subcellular compartments, such as with mitochondria or with the nucleus. Cells tend to defend themselves against any foreign material, which is taken up. In general, they try to eliminate particulate intruders and this is what they usually manage with micronsized particles. However, with NPs it is different. NPs may not be eliminated easily, and, hence may stimulate the cells to react in an unfavorable way. What we can learn is that NPs behave differently than microparticles.

Short term inhalation toxicity of a liquid aerosol of glutaraldehyde-coated CdS/Cd(OH)2 core shell quantum dots in rats

Quantum dots exhibit extraordinary optical and mechanical properties, and the number of their applications is increasing. In order to investigate a possible effect of coating on the inhalation toxicity of previously tested non-coated CdS/Cd(OH)2 quantum dots and translocation of these very small particles from the lungs, rats were exposed to coated quantum dots or CdCl2 aerosol (since Cd(2+) was present as impurity), 6h/d for 5 consecutive days. Cd content was determined in organs and excreta after the end of exposure and three weeks thereafter. Toxicity was determined by examination of broncho-alveolar lavage fluid and microscopic evaluation of the entire respiratory tract. There was no evidence for translocation of particles from the respiratory tract. Evidence of a minimal inflammatory process was observed by examination of broncho-alveolar lavage fluid. Microscopically, minimal to mild epithelial alteration was seen in the larynx. The effects observed with coated quantum dots, non-coated quantum dots and CdCl2 were comparable, indicating that quantum dots elicited no significant effects beyond the toxicity of the Cd(2+) ion itself. Compared to other compounds with larger particle size tested at similarly low concentrations, quantum dots caused much less pronounced toxicological effects. Therefore, the present data show that small particle sizes with corresponding high surfaces are not the only factor triggering the toxic response or translocation.