Inhalation toxicity profiles of particulate matter: a comparison between brake wear with other sources of emission.

Objective: There is substantial evidence that exposure to airborne particulate matter (PM) from road traffic is associated with adverse health outcomes. Although it is often assumed to be caused by vehicle exhaust emissions such as soot, other components may also contribute to detrimental effects. The toxicity of fine PM (PM2.5; <2.5 µm mass median aerodynamic diameter) released from brake pads was compared to PM from other sources. Materials and methods: PM2.5 of different types of brake pads (low-metallic, semi-metallic, NAO and ECE-NAO hybrid), tires and road pavement, poultry as well as the combustion of diesel fuel and wood (modern and old-fashioned stove technologies) were collected as suspensions in water. These were subsequently aerosolized for inhalation exposures. Female BALB/cOlaHsd mice were exposed for 1.5, 3, or 6 hours by nose-only inhalation up to 9 mg/m3. Results: Neither cytotoxicity nor oxidative stress was observed after exposure to any of the re-aerosolized PM2.5 samples. Though, at similar PM mass concentrations the potency to induce inflammatory responses was strongly dependent on the emission source. Exposure to most examined PM2.5 sources provoked inflammation including those derived from the poultry farm, wear emissions of the NAO and ECE-NAO hybrid brake pads as well as diesel and wood combustion, as indicated by neutrophil chemoattractant, KC and MIP-2 and lung neutrophil influx. Discussion and conclusions: Our study revealed considerable variability in the toxic potency of brake wear particles. Understanding of sources that are most harmful to health can provide valuable information for risk management strategies and could help decision-makers to develop more targeted air pollution regulation.

The impact of ambient air pollution on the human blood metabolome.

BACKGROUND: Biological perturbations caused by air pollution might be reflected in the compounds present in blood originating from air pollutants and endogenous metabolites influenced by air pollution (defined here as part of the blood metabolome). We aimed to assess the perturbation of the blood metabolome in response to short term exposure to air pollution. METHODS: We exposed 31 healthy volunteers to ambient air pollution for 5h. We measured exposure to particulate matter, particle number concentrations, absorbance, elemental/organic carbon, trace metals, secondary inorganic components, endotoxin content, gaseous pollutants, and particulate matter oxidative potential. We collected blood from the participants 2h before and 2 and 18h after exposure. We employed untargeted metabolite profiling to monitor 3873 metabolic features in 493 blood samples from these volunteers. We assessed lung function using spirometry and six acute phase proteins in peripheral blood. We assessed the association of the metabolic features with the measured air pollutants and with health markers that we previously observed to be associated with air pollution in this study. RESULTS: We observed 89 robust associations between air pollutants and metabolic features two hours after exposure and 118 robust associations 18h after exposure. Some of the metabolic features that were associated with air pollutants were also associated with acute health effects, especially changes in forced expiratory volume in 1s. We successfully identified tyrosine, guanosine, and hypoxanthine among the associated features. Bioinformatics approach Mummichog predicted enriched pathway activity in eight pathways, among which tyrosine metabolism. CONCLUSIONS: This study demonstrates for the first time the application of untargeted metabolite profiling to assess the impact of air pollution on the blood metabolome.

Characterizing the Chemical Profile of Incidental Ultrafine Particles for Toxicity Assessment Using an Aerosol Concentrator.

Incidental ultrafine particles (UFPs) constitute a key pollutant in industrial workplaces. However, characterizing their chemical properties for exposure and toxicity assessments still remains a challenge. In this work, the performance of an aerosol concentrator (Versatile Aerosol Concentration Enrichment System, VACES) was assessed to simultaneously sample UFPs on filter substrates (for chemical analysis) and as liquid suspensions (for toxicity assessment), in a high UFP concentration scenario. An industrial case study was selected where metal-containing UFPs were emitted during thermal spraying of ceramic coatings. Results evidenced the comparability of the VACES system with online monitors in terms of UFP particle mass (for concentrations up to 95 µg UFP/m3) and between filters and liquid suspensions, in terms of particle composition (for concentrations up to 1000 µg/m3). This supports the applicability of this tool for UFP collection in view of chemical and toxicological characterization for incidental UFPs. In the industrial setting evaluated, results showed that the spraying temperature was a driver of fractionation of metals between UF (<0.2 µm) and fine (0.2-2.5 µm) particles. Potentially health hazardous metals (Ni, Cr) were enriched in UFPs and depleted in the fine particle fraction. Metals vaporized at high temperatures and concentrated in the UF fraction through nucleation processes. Results evidenced the need to understand incidental particle formation mechanisms due to their direct implications on particle composition and, thus, exposure. It is advisable that personal exposure and subsequent risk assessments in occupational settings should include dedicated metrics to monitor UFPs (especially, incidental).

Inflammatory response in human alveolar epithelial cells after TiO2 NPs or ZnO NPs exposure: Inhibition of surfactant protein A expression as an indicator for loss of lung function.

The increasing use of metal oxide nanoparticles (MONPs) as TiO2 NPs or ZnO NPs has led to environmental release and human exposure. The respiratory system, effects on lamellar bodies and surfactant protein A (SP-A) of pneumocytes, can be importantly affected. Exposure of human alveolar epithelial cells (A549) induced differential responses; a higher persistence of TiO2 in cell surface and uptake (measured by Atomic Force Microscopy) and sustained inflammatory response (by means of TNF-α, IL-10, and IL-6 release) and ROS generation were observed, whereas ZnO showed a modest response and low numbers in cell surface. A reduction in SP-A levels at 24 h of exposure to TiO2 NPs (concentration-dependent) or ZnO NPs (the higher concentration) was also observed, reversed by blocking the inflammatory response (by the inhibition of IL-6). Loss of SP-A represents a relevant target of MONPs-induced inflammatory response that could contribute to cellular damage and loss of lung function.

Inflammation and tissue damage in mouse lung by single and repeated dosing of urban air coarse and fine particles collected from six European cities.

The authors have previously demonstrated heterogeneities in the inflammatory activities of urban air fine (PM(2.5-0.2)) and coarse (PM(10-2.5)) particulate samples collected from six European cities with contrasting air pollution situations. The same samples (10 mg/kg) were intratracheally instilled to healthy C57BL/6J mice either once or repeatedly on days 1, 3, and 6 of the study week. The lungs were lavaged 24 h after the single dose or after the last repeated dosing. In both size ranges, repeated dosing of particles increased the total cell number in bronchoalveolar lavage fluid (BALF) more than the respective single dose, whereas cytokine concentrations were lower after repeated dosing. The lactate dehydrogenase (LDH) responses increased up to 2-fold after repeated dosing of PM(2.5-0.2) samples and up to 6-fold after repeated dosing of PM(10-2.5) samples. PM(10-2.5) samples evoked a more extensive interstitial inflammation in the mouse lungs. The constituents with major contributions to the inflammatory responses were oxidized organic compounds and transition metals in PM(2.5-0.2) samples, Cu and soil minerals in PM(10-2.5) samples, and Zn in both size ranges. In contrast, poor biomass and coal combustion were associated with elevated levels of polycyclic aromatic hydrocarbons (PAHs) and a consistent inhibitory effect on the inflammatory activity of PM(2.5-0.2) samples. In conclusion, repeated intratracheal instillation of both fine and coarse particulate samples evoked enhanced pulmonary inflammation and cytotoxicity compared to single-dose administration. The sources and constituents of urban air particles responsible for these effects appear to be similar to those encountered in the authors' previous single-dose study.

Effects of short-term exposures to ultrafine particles near an airport in healthy subjects.

BACKGROUND: Recent studies reported elevated concentrations of ultrafine particles (UFP) near airports. Little is known about the health effects of UFP from aviation. Since UFP can deposit deep into the lungs and other organs, they may cause significant adverse health effects. OBJECTIVE: We investigated health effects of controlled short-term human exposure to UFP near a major airport. METHODS: In this study, 21 healthy non-smoking volunteers (age range: 18-35 years) were repeatedly (2-5 visits) exposed for 5 h to ambient air near Schiphol Airport, while performing intermittent moderate exercise (i.e. cycling). Pre- to post-exposure changes in cardiopulmonary outcomes (spirometry, forced exhaled nitric oxide, electrocardiography and blood pressure) were assessed and related to total- and size-specific particle number concentrations (PNC), using linear mixed effect models. RESULTS: The PNC was on average 53,500 particles/cm3 (range 10,500-173,200). A 5-95th percentile increase in exposure to UFP (i.e. 125,400 particles/cm3) was associated with a decrease in FVC of -73.8 mL (95% CI -138.8 - -0.4) and a prolongation of the corrected QT (QTc) interval by 9.9 ms (95% CI 2.0 - 19.1). These effects were associated with particles < 20 nm (mainly UFP from aviation), but not with particles > 50 nm (mainly UFP from road traffic). DISCUSSION: Short-term exposures to aviation-related UFP near a major airport, was associated with decreased lung function (mainly FVC) and a prolonged QTc interval in healthy volunteers. The effects were relatively small, however, they appeared after single exposures of 5 h in young healthy adults. As this study cannot make any inferences about long-term health impacts, appropriate studies investigating potential health effects of long-term exposure to airport-related UFP, are urgently needed.

Subchronic inhalation of mixtures of cigarette smoke constituents in Xpa-/-p53+/- knock-out mice: a comparison of intermittent with semi-continuous exposure to acetaldehyde, formaldehyde, and acrolein.

We investigated whether inhaling peak concentrations of aldehydes several times daily is more damaging than semi-continuously inhaling low-dose aldehydes. We exposed Xpa-/-p53+/- knock-out mice either intermittently or semi-continuously to mixed acetaldehyde, formaldehyde, and acrolein. The intermittent regimen entailed exposure to the aldehydes 7 min every 45 min, 12 times/day, 5 days/week, corresponding to concentrations inhaled by smokers. Semi-continuously exposed animals received half the dose of aldehydes in 8h/day, 5 days/week. Some mice in each group were sacrificed after 13 weeks of exposure; the rest breathed clean air until the end of 1 year. Mice injected intratracheally with benzo[a]pyrene formed a positive control group. The nasal cavity, lungs, and any macroscopically abnormal organs of all mice were analysed histopathologically. After 13 weeks of exposure, the subacute, overall, histopathological changes induced by the inhalation differed noticeably between the intermittently and semi-continuously treated Xpa-/-p53+/- knock-out mice. After 13 weeks of mixed aldehyde exposure, atrophy of the olfactory epithelium generally appeared, but disappeared after 1 year (adaptation and/or recovery). Respiratory epithelial metaplasia of the olfactory epithelium occurred at a higher incidence at 1 year. Except for a significantly greater number of tumours observed in knock-out mice compared to wild mice (semi-continuous aldehyde exposure and controls), no differences between the semi-continuous and intermittent exposure groups were observed.

Importance of size and composition of particles for effects on cells in vitro.

A primary goal of current research on particle-induced health effects is to reveal the critical characteristics that determine their biological effects. Experimental studies have shown that smaller particles induce stronger biological effects than larger particles of similar composition, due to their larger surface area to mass ratio. However, correlation for variations in surface area could not account for variation in biological reactivity among particles of differential composition. Hence, the importance of size and surface area does not override the importance of particle composition. Moreover, different particle characteristics appear to be involved in different biological effects in vitro. Our studies show that mineral particle-induced apoptosis mostly seems to depend on particle size, whereas composition and surface reactivity appeared to be most important for the proinflammatory potential of the particles. The ability of the particles to generate reactive oxygen species in vitro was not correlated with either inflammatory markers or apoptosis, suggesting that other mechanisms are at play. A single, specific component of the mineral particles, explaining the differences in response, has not been identified. In European-wide studies such as the Respiratory Allergy and Inflammation due to Air Pollution (RAIAP) study, particles have been sampled in different locations to study season- and site-dependent variations in responses particles, such as markers of inflammatory and allergic reactions in cells and animals. The data indicate that coarse particles can induce at least as strong inflammatory responses as fine particles. The allergic responses tended to be more associated with the organic fraction (PAH) of particles, whereas the inflammatory reactions seemed to be more associated with metals and endotoxin. Overall, coarse PM was found to have an inflammatory potential similar to fine PM on an equal mass basis. Even though one has to take into account different concentrations in ambient air as well as differences in respiratory system deposition of the size fractions, the potential of coarse particles to induce pulmonary effects should not be neglected.

Signal transduction pathways involved in particulate matter induced relaxation in rat aorta--spontaneous hypertensive versus Wistar Kyoto rats.

UNLABELLED: Previously we reported that in vivo exposure to ambient particulate matter (PM) induces vasodilatation in rat aorta. The purpose of the current study was to investigate the intracellular messengers involved in PM-elicited vasodilatation in aortas from spontaneous hypertensive (SHR) and normotensive (WKY) rats. METHODS: The contribution of three different intracellular pathways, i.e. (1) the NO-cGMP pathway, (2) prostanoids signaling and (3) endothelial hyperpolarisation factors were evaluated by using specific inhibitors (NS2028, Diclofenac and high K-concentration/17-ODYA, respectively). Using antagonists of capsaicin- or histamine receptors we tested potential interactions of PM with these receptors. Particle suspensions (EHC-93), particle filtrates (particle-free) and Cu(2+)- or Zn(2+)-containing solutions were used to obtain cumulative dose-response curves of relaxation in normal and endothelium-denuded rings. RESULTS: Our present data confirm that PM and its soluble components elicit an endothelium-independent vasodilatation in rat aorta rings. The response is mainly linked to the activation of soluble guanylate cyclase (sGC), since its inhibition by NS2028 almost abolished relaxation. Indeed PM suspensions stimulated cGMP production in purified isolated sGC. Neither the receptor nor their signaling pathways played a significant role in the direct relaxation by PM or metals. Vasodilatation responses were significantly higher in SHR than WKY control rats. CONCLUSION: Our data demonstrate that PM elicits a dose-dependent vasodilatation via activation of sGC in vascular smooth muscles. PM components, including soluble transition metals play a major role in this response. The stronger effect in SHR rats is in accordance with the observation that acute effects of PM are mainly seen in patients with underlying cardiovascular diseases.

Toxicology of chemical mixtures: international perspective.

This paper reviews major activities outside the United States on human health issues related to chemical mixtures. In Europe an international study group on combination effects has been formed and has started by defining synergism and antagonism. Successful research programs in Europe include the development and application of statistically designed experiments combined with multivariate data analysis and modeling in vitro and in vivo studies on a wide variety of chemicals such as petroleum hydrocarbons, aldehydes, food contaminants, industrial solvents, and mycotoxins. Other major activities focus on the development of safety evaluation strategies for mixtures such as the use of toxic equivalence factors or alternatives such as the question-and-answer approach, fractionation followed by recombination of the mixture in combination with a mixture design, and quantitative structure-activity relationship analysis combined with lumping analysis and physiologically based pharmacokinetic/pharmacodynamic modeling for studying complex mixtures. A scheme for hazard identification and risk assessment of complex mixtures and a consistent way to generate total volatile organic compound values for indoor air have also been developed. Examples of other activities are carcinogenicity studies on complex mixtures (petroleum middle distillates, foundry fumes, pesticides, heterocyclic amines, diesel exhaust, solid particles), neurotoxicity studies of mixtures of solvents alone or in combination with exposure to physical factors, and toxicity studies of outdoor air pollutants, focusing on particulates. Outside the United States, toxicologists and regulators clearly have a growing interest in the toxicology and risk assessment of chemical mixtures.

Toxicology of chemical mixtures: challenges for today and the future.

A major challenge for the toxicologist involved in safety evaluation of chemical mixtures is to test the hypothesis that as a rule exposure to mixtures of chemicals at (low) non-toxic doses of the individual chemicals is of no health concern. A series of repeated dose studies in rats with defined mixtures of chemicals with the same or different target organs revealed that exposure to a combination of chemicals compared with exposure to the individual compounds did not constitute an evidently increased hazard, provided each chemical was administered at a level similar to, or slightly lower than, its own 'No-Observed-Adverse-Effect-Level'. The results of subacute oral toxicity studies in rats with defined mixtures of nephrotoxicants with similar mode of action underlined the applicability of the additivity assumption for a mixture of chemicals with simple similar action. Safety evaluation of complex chemical mixtures is a challenge that can be tackled as follows: first, identify the (e.g. ten) most risky chemicals in the mixture, and, second, assess the hazard and the potential health risk of the mixture of the most risky chemicals, using procedures developed for defined mixtures. To identify interactions between individual compounds, a most promising testing strategy appeared to be a statistical approach using a fractional two-level factorial design. A challenge for today and the future is to gradually substitute mixture-oriented (real life-oriented) standard setting for (unrealistic) single chemical-oriented standard setting.

Biochemical and histopathological changes in nasal epithelium of rats after 3-day intermittent exposure to formaldehyde and ozone alone or in combination.

To get a better insight into the pathophysiology of the nasal changes induced by formaldehyde-ozone mixtures, a 3-day inhalation study was carried out in rats, using intermittent exposure to formaldehyde (3.6 ppm) and ozone (0.4 ppm) alone or in combination and focusing on biochemical and histopathological changes in rat nasal respiratory epithelium. Formaldehyde dehydrogenase, glutathione S-transferase, glutathione reductase, and glucose-6-phosphate dehydrogenase activities in this epithelium were not affected by the individual compounds. However, combined exposure to formaldehyde and ozone resulted in slightly decreased activities of these enzymes. Formaldehyde was found to induce rhinitis, degeneration, frank necrosis, hyperplasia and squamous metaplasia of the ciliated and non-ciliated nasal respiratory epithelium, while ozone induced disarrangement, flattening and slight basal cell hyperplasia of the non-ciliated cuboidal epithelium accompanied by influx of neutrophils. Proliferating cell nuclear antigen (PCNA) expression was elevated not only in nasal areas showing ozone-induced histopathological changes but also in the otherwise normal-appearing epithelium of the nasal septum. No interactive effects were found with respect to proliferative response of the nasal respiratory epithelium after exposure to the formaldehyde-ozone mixture. The present study did not provide evidence of a major role of glutathione and glutathione-dependent enzymes in the pathogenesis of nasal lesions induced by formaldehyde and/or ozone, demonstrated the potential of ozone to affect the mucociliary epithelium lining the nasal septum, and suggested that PCNA expression is a sensitive tool for detection of early effects of respiratory irritants.

Ambient fine and coarse particle suppression of alveolar macrophage functions.

Alveolar macrophages (AM) are part of the innate immunological defense system and are among the first cells to respond to the effects of inhaled particles. Study of macrophage responses to particles is, therefore, relevant to understanding the mechanisms by which inhaled particles can adversely affect health. Size-fractionated ambient particles were collected at traffic-dominated sites in The Netherlands using a mobile high volume slit impactor system. AM were obtained by bronchoalveolar lavage from adult as well as aged rats and were incubated with for 4 h with collected particles at concentrations of 25-1000 pg per cell. Free radical generation by AM was measured with and without stimulation of AM with phorbol myristate acetate (PMA). There were dose-dependent decreases in macrophage production of superoxide radicals as measured by the chemiluminescent method. Coarse particles were more toxic than were fine particles. Suppression of free radical production did not seem to be related to the presence of bioavailable iron or to endotoxin associated with the particles. There were no statistically significant differences related to age or strain of the rats tested. We conclude that in vitro tests using AM is a useful and rapid method for delineating differences in toxicity between environmental samples of size fractionated ambient particles.

Safety evaluation of the mixture of chemicals at a specific workplace: theoretical considerations and a suggested two-step procedure.

Procedures for the selection of compounds with high health hazard potential are reviewed, and major aspects of the assessment of health risks associated with exposure to mixtures of chemicals are discussed. Examples are given of additivity and synergism of effects following exposure to mixtures. Using these data from the literature a two-step procedure for the safety evaluation of the mixture of chemicals occurring at a specific workplace is suggested. The first step consists of estimating the relative health risk associated with each chemical; the estimation is based on the ratio between exposure level and degree of toxicity. Those chemicals representing a high risk are then selected for further consideration. The second step comprises the risk assessment, focusing on prediction of the risk associated with exposure to the mixture of selected chemicals. To allow such prediction the (presumable) mode of action of the selected compounds should be considered. A practical way to find out whether exposure to chemicals at a specific workplace is of serious health concern, could be the conduct of both a 4-week toxicity study in rats and 2 different types of genotoxicity studies with the mixture of selected chemicals, using exposure concentrations related to those occurring in practice.

Toxicity studies in rats of simple mixtures of chemicals with the same or different target organs.

Mixtures of chemicals with different target organs or the same target organ but different target sites or different modes of action did not appear to be distinctly more hazardous than the individual chemicals, provided the dose level of each chemical in the mixture did not exceed its own 'No-Observed-Adverse-Effect Level'. Clearly, for such mixtures and exposure conditions the additivity assumption did not hold. However, the additivity rule appeared to be applicable to mixtures of chemicals with the same target organ and the same mechanism of action or receptor. Fractional 2-factorial study designs were found to be promising tools for examining possible combined actions or interactions of chemicals in a mixture.

Aldehydes: occurrence, carcinogenic potential, mechanism of action and risk assessment.

Aldehydes constitute a group of relatively reactive organic compounds. They occur as natural (flavoring) constituents in a wide variety of foods and food components, often in relatively small, but occasionally in very large concentrations, and are also widely used as food additives. Evidence of carcinogenic potential in experimental animals is convincing for formaldehyde and acetaldehyde, limited for crotonaldehyde, furfural and glycidaldehyde, doubtful for malondialdehyde, very weak for acrolein and absent for vanillin. Formaldehyde carcinogenesis is a high-dose phenomenon in which the cytotoxicity plays a crucial role. Cytotoxicity may also be of major importance in acetaldehyde carcinogenesis but further studies are needed to prove or disprove this assumption. For a large number of aldehydes (relevant) data on neither carcinogenicity nor genotoxicity are available. From epidemiological studies there is no convincing evidence of aldehyde exposure being related to cancer in humans. Overall assessment of the cancer risk of aldehydes in the diet leads to the conclusion that formaldehyde, acrolein, citral and vanillin are no dietary risk factors, and that the opposite may be true for acetaldehyde, crotonaldehyde and furfural. Malondialdehyde, glycidaldehyde, benzaldehyde, cinnamaldehyde and anisaldehyde cannot be evaluated on the basis of the available data. A series of aldehydes should be subjected to at least mutagenicity, cytogenicity and cytotoxicity tests. Priority setting for testing should be based on expected mechanism of action and degree of human exposure.

Release of inflammatory cytokines, cell toxicity and apoptosis in epithelial lung cells after exposure to ambient air particles of different size fractions.

Several studies have shown that particles of smaller size may be more potent than larger to induce inflammatory and toxic responses in cultured lung cells. However, the relative importance of different size fractions of ambient PM to induce such effects is still not known. In this study, we investigated the potency of different size fractions of urban ambient air particles to induce release of inflammatory cytokines in the human alveolar cell line A549 and primary rat type 2 cells. A mineral-rich ambient air PM10 sample collected in a road tunnel (road PM10) was also included. The coarse fraction of the urban ambient air particles demonstrated a similar or higher potency to induce release of the proinflammatory cytokines IL-8/MIP-2 and IL-6 compared to the fine and ultrafine fractions. The coarse fraction was also the most toxic in both cell systems. In contrast to the A549 cells, no induction of cytokine release was induced by the ultrafine particles in the primary type 2 cells. The mineral-rich road PM10 may be equally or more potent than the various size fractions of the ambient air particles to induce cytokines in both cell types. In conclusion, the coarse fraction of ambient particles may be at least as potent by mass as smaller fractions to induce inflammatory and toxic effects in lung cells.

Toxicity of formaldehyde and acrolein mixtures: in vitro studies using nasal epithelial cells.

In vitro studies with human and rat nasal epithelial cells were carried out to investigate the combined toxicity of formaldehyde and acrolein and the role of aldehyde dehydrogenases in this process. These studies showed that the toxic effect of mixtures of aldehydes was additive. In addition, aldehyde dehydrogenases were inhibited by disulfiram and acrolein in S9 incubation but disulfiram did not influence the toxicity in vitro (cell culture). This study does not support the idea that aldehyde dehydrogenases play a major role in the detoxification of exogenous aldehydes.

Investigation of the effects of short-term inhalation of carbon nanoparticles on brains and lungs of c57bl/6j and p47(phox-/-) mice.

Recent studies indicate that the brain is a target for toxic carbonaceous nanoparticles present in ambient air. It has been proposed that the neurotoxic effects of such particles are driven by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase mediated generation of reactive oxygen species (ROS) in activated microglia. In the present study, we have evaluated the effects of short term (4h) nose-only inhalation exposure to carbon NP (CNP) in the brains and lungs of C57BL/6J mice and in p47(phox-/-) mice that lack a functional NADPH oxidase. It was shown that the lungs of the p47(phox-/-) mice are less responsive to CNP inhalation than lungs of the corresponding C57BL/6J control animals. Lung tissue mRNA expression of the oxidative stress/DNA damage response genes 8-oxoguanine glycosylase (OGG1) and apurinic/apyrimidinic endonuclease 1 (APE1) were induced by CNP exposure in C57BL/6J but not in the p47(phox-/-) mice. In contrast, the expression of these genes, as well as Tumor Necrosis Factor-α (TNFα), Cyclooxygenase-2 (COX-2) and Heme Oxygenase-1 (HO-1) was not altered in the olfactory bulb, cerebellum or remaining brain tissue part of either mouse background. This indicates that neuroinflammation was not induced by this exposure. CNP inhalation for 4h or for 4h on three consecutive days also did not affect brain tissue protein expression of interleukin (IL)-1ß, while a clear significant difference in constitutive expression level of this pro-inflammatory cytokine was found between C57BL/6J and p47(phox-/-) mice. In conclusion, short-term inhalation exposure to pure carbon nanoparticles can trigger mild p47(phox) dependent oxidative stress responses in the lungs of mice whereas in their brains at the same exposure levels signs of oxidative stress and inflammation remain absent. The possible role of p47(phox) in the neuro-inflammatory effects of nanoparticles in vivo remains to be clarified.

Short-term effects of PM2.5, PM10 and PM2.5-10 on daily mortality in The Netherlands.

INTRODUCTION: Information on the relationship between levels of particulate matter (PM) smaller than 2.5 µm and mortality rates in Europe is relatively sparse because of limited availability of PM2.5 measurement data. Even less information is available on the health effects attributable to PM2.5-10, especially for North-West Europe. OBJECTIVES: To investigate the relationship between various PM size fractions and daily mortality rates. METHODS: Daily concentrations of PM from the Dutch National Ambient Air Quality Monitoring Network as well as all cause and cause-specific mortality rates in The Netherlands were obtained for the period 2008-2009. Poisson regression analysis using generalized additive models was used, with adjustment for potential confounding including long-term and seasonal trends, influenza incidence, meteorological variables, day of the week, and holidays. Different measures of PM (PM2.5, PM10 and PM2.5-10) were analysed. RESULTS: PM10 and PM2.5 levels were statistically significantly (p<0.05) associated with all cause and cause-specific deaths. For example, a 10 µg/m(3) increase in previous day PM was associated with 0.8% (95% CI 0.3-1.2) excess risk in all cause mortality for PM2.5 and a 0.6% (CI 0.2-1.0) excess risk for PM10. No appreciable associations were observed for PM2.5-10. Effects of PM10, and PM2.5 were insensitive to adjustment for PM2.5-10, and vice-versa. PM10 and PM2.5 were too highly correlated to disentangle their independent effects. CONCLUSIONS: PM10 and PM2.5 both were significantly associated with all cause and cause-specific mortality. We were unable to demonstrate significant effects for PM2.5-10, possibly due to the lower temporal variability and the higher exposure misclassification in PM2.5-10 compared to PM10 or PM2.5. The lack of effects of PM2.5-10 in our study should therefore not be interpreted as an indication that PM2.5-10 can be considered harmless.