Cellular and biochemical response of the human lung after intrapulmonary instillation of ferric oxide particles

Inflammation related to inhalation of nano and micron sized iron oxides: a systematic review

Inhalation exposure to iron oxide occurs in many workplaces and respirable aerosols occur during thermal processes (e.g. welding, casting) or during abrasion of iron and steel products (e.g. cutting, grinding, machining, polishing, sanding) or during handling of iron oxide pigments. There is limited evidence of adverse effects in humans specifically linked to inhalation of iron oxides. This contrasts to oxides of other metals used to alloy or for coating of steel and iron of which several have been classified as being hazardous by international and national agencies. Such metal oxides are often present in the air at workplaces. In general, iron oxides might therefore be regarded as low-toxicity, low-solubility (LTLS) particles, and are often considered to be nontoxic even if very high and prolonged inhalation exposures might result in diseases. In animal studies, such exposures lead to cancer, fibrosis and other diseases. Our hypothesis was that pulmonary-workplace exposure during manufacture and handling of SPION preparations might be harmful. We therefore conducted a systematic review of the relevant literature to understand how iron oxides deposited in the lung are related to acute and subchronic pulmonary inflammation. We included one human and several in vivo animal studies published up to February 2023. We found 25 relevant studies that were useful for deriving occupational exposure limits (OEL) for iron oxides based on an inflammatory reaction. Our review of the scientific literature indicates that lowering of health-based occupational exposure limits might be considered.

Automated SEM/EDX imaging for the in-depth characterization of non-exhaust traffic emissions from the Munich subway system

A SEM/EDX based automated measurement and classification algorithm was tested as a method for the in-depth analysis of micro-environments in the Munich subway using a custom build mobile measurements system. Sampling was conducted at platform stations, to investigate the personal exposure of commuters to subway particulate matter during platform stays. EDX spectra and morphological features of all analyzed particles were automatically obtained and particles were automatically classified based on pre-defined chemical and morphological boundaries. Source apportionment for individual particles, such as abrasion processes at the wheel-brake interface, was partially possible based on the established particle classes. An average of 98.87 ± 1.06 % of over 200,000 analyzed particles were automatically assigned to the pre-defined classes, with 84.68 ± 16.45 % of particles classified as highly ferruginous. Manual EDX analysis further revealed, that heavy metal rich particles were also present in the ultrafine size range well below 100 nm.

Air pollution and risk of respiratory and cardiovascular hospitalizations in a large city of the Mekong Delta Region

It is important to explore air pollution and health effects in developing cities for early prevention rather than waiting for conditions to deteriorate as in the current megacities. This study aims to investigate the short-term health effects of air pollution in a large city in the Mekong Delta Region (MDR) of Vietnam. Air pollution data from January 2015 to December 2018 were collected from the Environmental Monitoring Centre of Can Tho City. The data of respiratory and cardiovascular disease (CVD) admissions in 18 hospitals and medical centers were collected. A time-series regression analysis was conducted using distributed lag models to examine the relationship between the air pollutants and hospitalizations including the delayed effect up to 7 days. The research findings reveal that a 10 μg increase in PM₁₀ was associated with an increase of 2.5% in the risk of respiratory admission for all people and 2.2% in the risk of CVD admission for the elderly on the same day. The analysis stratified by age and sex indicates that PM10 resulted in a higher risk of respiratory admission among children (0-5 years old) and males compared with other groups. PM10 and NO₂ were significantly associated with CVD admission among the elderly at lag 4 and 6 days. The effects of other air pollutants (SO₂, O₃) were not observed in this study. As development continues in this region, there is an urgent need for intervention measures to minimize the health impacts associated with the expected increases in air pollution in the MDR.

Effect of ambient fine particulates (PM2.5) on hospital admissions for respiratory and cardiovascular diseases in Wuhan, China

Background

Positive associations between ambient PM_2.5 and cardiorespiratory disease have been well demonstrated during the past decade. However, few studies have examined the adverse effects of PM_2.5 based on an entire population of a megalopolis. In addition, most studies in China have used averaged data, which results in variations between monitoring and personal exposure values, creating an inherent and unavoidable type of measurement error.

Methods

This study was conducted in Wuhan, a megacity in central China with about 10.9 million people. Daily hospital admission records, from October 2016 to December 2018, were obtained from the Wuhan Information center of Health and Family Planning, which administrates all hospitals in Wuhan. Daily air pollution concentrations and weather variables in Wuhan during the study period were collected. We developed a land use regression model (LUR) to assess individual PM_2.5 exposure. Time-stratified case-crossover design and conditional logistic regression models were adopted to estimate cardiorespiratory hospitalization risks associated with short-term exposure to PM_2.5. We also conducted stratification analyses by age, sex, and season.

Results

A total of 2,806,115 hospital admissions records were collected during the study period, from which we identified 332,090 cardiovascular disease admissions and 159,365 respiratory disease admissions. Short-term exposure to PM_2.5 was associated with an increased risk of a cardiorespiratory hospital admission. A 10 μg/m³ increase in PM_2.5 (lag0–2 days) was associated with an increase in hospital admissions of 1.23% (95% CI 1.01–1.45%) and 1.95% (95% CI 1.63–2.27%) for cardiovascular and respiratory diseases, respectively. The elderly were at higher PM-induced risk. The associations appeared to be more evident in the cold season than in the warm season.

Conclusions

This study contributes evidence of short-term effects of PM_2.5 on cardiorespiratory hospital admissions, which may be helpful for air pollution control and disease prevention in Wuhan.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01731-x.

Endogenous doesn't always mean innocuous: a scoping review of iron toxicity by inhalation

Ambient air pollution is a leading risk factor for the global burden of disease. One possible pathway of particulate matter (PM)-induced toxicity is through iron (Fe), the most abundant metal in the atmosphere. The aim of the review was to consider the complexity of Fe-mediated toxicity following inhalation exposure focusing on the chemical and surface reactivity of Fe as a transition metal and possible pathways of toxicity via reactive oxygen species (ROS) generation as well as considerations of size, morphology, and source of PM. A broad term search of 4 databases identified 2189 journal articles and reports examining exposure to Fe via inhalation in the past 10 years. These were sequentially analyzed by title, abstract and full-text to identify 87 articles publishing results on the toxicity of Fe-containing PM by inhalation or instillation to the respiratory system. The remaining 87 papers were examined to summarize research dealing with in vitro, in vivo and epidemiological studies involving PM containing Fe or iron oxide following inhalation or instillation. The major findings from these investigations are summarized and tabulated. Epidemiological studies showed that exposure to Fe oxide is correlated with an increased incidence of cancer, cardiovascular diseases, and several respiratory diseases. Iron PM was found to induce inflammatory effects in vitro and in vivo and to translocate to remote locations including the brain following inhalation. A potential pathway for the PM-containing Fe-mediated toxicity by inhalation is via the generation of ROS which leads to lipid peroxidation and DNA and protein oxidation. Our recommendations include an expansion of epidemiological, in vivo and in vitro studies, integrating research improvements outlined in this review, such as the method of particle preparation, cell line type, and animal model, to enhance our understanding of the complex biological interactions of these particles.

The association of short-term effects of air pollution and sleep disorders among elderly residents in China

Sleep disorders, oftentimes co-occurring with other mental and neurological disorders in the elderly, have been previously linked to short-term exposures to air pollution. Here we assessed such associations among 395,651 elderly Chinese in Ningbo, China where air pollution exposures are high and the proportion of elderly in the population is growing. We utilized a regional health information database in China (2008-2017) that collected information on hospital visits for sleep disorders among the elderly (age 60+). Measures of daily air pollution concentrations including nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), inhalable particles (PM₁₀), and ambient fine particulate matter (PM_2.5) were generated from seven environmental air quality monitoring sites in the study area. We used a generalized additive model to evaluate the associations between hospital visits for sleep disorders and short-term air pollution exposures for up to 7 days prior to a hospital visit. Short-term exposure to multiple air pollutants was associated with hospital visits for sleep disorders in an elderly population; with the strongest associations during 2-3 days prior to a clinic visits for traffic-related pollutants including air quality index (AQI), PM_2.5, PM₁₀, and NO₂ and for SO₂ and O₃ for 5 days prior to the visits. Our study based on large health care record system suggested that short-term air pollution exposures are associated with sleep disorders in the elderly. Considering the individual covariates that could not be adjusted in time-series analyses, future studies with individual level data and an ability to evaluate the severity of sleep disorders and their relation to mental and physical health in general and air pollution are needed. An aging population with increasing health problems and the frequency of high and very high air pollution events in China make our findings very health policy relevant.

Respiratory and cardiovascular effects of metals in ambient particulate matter: a critical review

In this review, we critically evaluated the epidemiological and toxicological evidence for the role of specific transition metals (As. Cr. Cu. Fe. Mn. Ni. Sc. Ti. V and Zn) in causing or contributing to the respiratory and cardiovascular health effects associated with ambient PM. Although the epidemiologic studies arc suggestive. and both the in vivo and in vitro laboratory studies document the toxicity of specific metals (Fe. Ni. V and Zn). the overall weight of evidence does not convincingly implicate metals as major contributors to health effects. None of the epidemiology studies that we reviewed conclusively implicated specific transition metals as having caused the respiratory and cardiovascular effects associated with ambient levels of PM. However, the studies reviewed tended to be internal ly consistent in identifying some metals (Fe, Ni, V and Zn) more frequently than others (As, Cu, Mn and Sc) as having positive associations wi th health effects. The major problem wi th which the epidemiological studies were faced was classifying and quantifying exposure. Community and population exposures to metals or other components of ambient PM were inferred from centrally- located samplers that may not accurately represent individual level exposures. Only a few authors reported findings that did not support the stated premise of the study; indeed, statistic ally significant associations are not necessarily biologically significant. It is likely that ·'negative studies" are under-represented in the published literature, making it a challenge to achieve a balanced evaluation of the role of metals in causing health effects associated with ambient PM. Both the in vivo and in vitro study results demonstrated that individual metals (Cu. Fe. Ni. V and Zn) and extracts of metals from ambient PM sources can produce acute inflammatory responses. However. the doses administered to laboratory animals were many orders of magnitude greater than what humans experience from breathing ambient air. The studies that used intratracheal instillation have the advantage of delivering a known dose to a specific anatomical location. but arc not analogous to an inhaled dose that is distributed over the surface area of the respiratory tract. Studies. in which laboratory animals or human volunteers inhaled CAPs best represent exposures to the general human population. The in vivo and in vitro studies reviewed provide indications that the probable mechanisms involved in the respiratory and cardiac effects from high metal exposures include: an inflammatory response mediated by formation of ROS, upregulation of genes coding for inflammatory cytokines, altered expression of genes involved in cell signaling pathways and maintenance of metals homeostasis.The fact that doses of metals many orders of magnitude greater than those existing in ambient air were required to produce measurable adverse effects in animals makes it doubtful that metals play any major role in respiratory and cardiovascular effects produced from human exposure to ambient PM. We suggest that future research priorities should focus on testing at more environmentally relevant exposure levels and that any new toxicological studies be written to include dosages in units that can be easily compared to human exposure levels.

Human inhalation exposure to iron oxide particles

In the past decade, many studies have been conducted to determine the health effects induced by exposure to engineered nanomaterials (NMs). Specifically for exposure via inhalation, numerous in vitro and animal in vivo inhalation toxicity studies on several types of NMs have been published. However, these results are not easily extrapolated to judge the effects of inhaling NMs in humans, and few published studies on the human response to inhalation of NMs exist. Given the emergence of more industries utilizing iron oxide nanoparticles as well as more nanomedicine applications of superparamagnetic iron oxide nanoparticles (SPIONs), this review presents an overview of the inhalation studies that have been conducted in humans on iron oxides. Both occupational exposure studies on complex iron oxide dusts and fumes, as well as human clinical studies on aerosolized, micron-size iron oxide particles are discussed. Iron oxide particles have not been described to elicit acute inhalation response nor promote lung disease after chronic exposure. The few human clinical studies comparing inhalation of fine and ultrafine metal oxide particles report no acute changes in the health parameters measured. Taken together existing evidence suggests that controlled human exposure to iron oxide nanoparticles, such as SPIONs, could be conducted safely.

In vitro adverse effects of iron ore dusts on human lymphoblastoid cells in culture

The aim of this study was to investigate the adverse effects produced by four types of iron (Fe) ore dust using cultured human cells. Genotoxicity and cytotoxicity induced by Fe ore dusts were determined by assays including cytokinesis block micronucleus (CBMN), population growth, and methyl tetrazolium (MTT). Four iron ore dusts were tested, namely, 1002 Limonite & Goethite (1002), HG2 hematite (HG2), HG1 Soutlem Pit (HG1), and HG4. WIL2 -NS cells were incubated for 10 h with extracts from a range of concentrations (0, 75, or 150 μg/ml) of Fe ore dust. Significant decreases in percent cell viability were seen at 150 μg/ml HG2 and 1002 as measured by MTT, with viability that decreased to 75 and 73%, respectively, compared to untreated controls. The cell population regrew to a different extent after Fe ore dust was removed, except for HG1, where population remained declined. An approximately twofold significant increase in the frequency of micronucleated binucleated cells (MNBNC) was seen with 1002, HG2, and HG1 at 150 μg/ml. A significant rise in apoptosis induction was observed at 150 μg/ml HG1. Data indicate that Fe ore dusts at 150 μg/ml produced cytotoxicity and genotoxicity.

Characterization of coal fly ash nanoparticles and induced oxidative DNA damage in human peripheral blood mononuclear cells

The nano-sized particles present in coal fly ash (CFA) were characterized through the X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM, SEM), atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) analyses. The XRD data revealed the average crystallite size of the CFA nanoparticles (CFA-NPs) as 14 nm. TEM and SEM imaging demonstrated predominantly spherical and some polymorphic structures in the size range of 11 to 25 nm. The amount of heavy metal associated with CFA particles (μg/g) were determined as Fe (34160.0±1.38), Ni (150.8±0.78), Cu (99.3±0.56) and Cr (64.0±0.86). However, the bioavailability of heavy metals in terms of percent release was in the order as Cr>Ni>Cu>Fe in CFA-dimethyl sulfoxide (DMSO) extract. The comet and cytokinesis blocked micronucleus (CBMN) assays revealed substantial genomic DNA damage in peripheral blood mononuclear (PBMN) cells treated with CFA-NPs in Aq and DMSO extracts. About 1.8 and 3.6 strand breaks per unit of DNA were estimated through alkaline unwinding assay at 1:100 DNA nucleotide/CFA ppm ratios with the Aq and DMSO extracts, respectively. The DNA and mitochondrial damage was invariably greater with CFA-DMSO extract vis-à-vis -Aq extract. Generation of superoxide anions (O(2)•(-)) and intracellular reactive oxygen species (ROS) through metal redox-cycling, alteration in mitochondrial potential and 8-oxodG production elucidated CFA-NPs induced oxidative stress as a plausible mechanism for CFA-induced genotoxicity.

Oxidative stress and inflammatory responses of rat following acute inhalation exposure to iron oxide nanoparticles

In this research, we investigated the toxicity responses of rat following a continuous 4 h inhalation exposure of only the head and nose to iron oxide nanoparticles (Fe(3)O(4) NPs, size = 15-20 nm). The rats for the investigation were exposed to a concentration of 640 mg/m(3) Fe(3)O(4) NPs. Markers of lung injury and proinflammatory cytokines (interleukin-1β, tumor necrosis factor-α, and interleukin-6) in bronchoalveolar lavage fluid (BALF) and blood, oxidative stress in lungs, and histopathology were assessed on 24 h, 48 h, and 14 days of postexposure periods. Our results showed a significant decrease in the cell viability, with the increase in the levels of lactate dehydrogenase, total protein, and alkaline phosphatase in the BALF. Total leukocyte count and the percentage of neutrophils in BALF increased within 24 h of postexposure. Immediately following acute exposure, rats showed increased inflammation with significantly higher levels of lavage and blood proinflammatory cytokines and were consistent throughout the observation period. Fe(3)O(4) NPs exposure markedly increased malondialdehyde concentration, while intracellular reduced glutathione and antioxidant enzyme activities were significantly decreased in lung tissue within 24-h postexposure period. On histological observation, the lung showed an early activation of pulmonary clearance and a size-dependant biphasic nature of the Fe(3)O(4) NPs in causing the structural alteration. Collectively, our data illustrate that Fe(3)O(4) NPs inhalation exposure may induce cytotoxicity via oxidative stress and lead to biphasic inflammatory responses in Wistar rat.

Hematite nanoparticles larger than 90 nm show no sign of toxicity in terms of lactate dehydrogenase release, nitric oxide generation, apoptosis, and comet assay in murine alveolar macrophages and human lung epithelial cells

Three hematite samples were synthesized by precipitation from a FeCl₃ solution under controlled pH and temperature conditions in different morphology and dimensions: (i) microsized (average diameter 1.2 μm); (ii) submicrosized (250 nm); and (iii) nanosized (90 nm). To gain insight into reactions potentially occurring in vivo at the particle-lung interface following dust inhalation, several physicochemical features relevant to pathogenicity were measured (free radical generation in cell-free tests, metal release, and antioxidant depletion), and cellular toxicity assays on human lung epithelial cells (A549) and murine alveolar macrophages (MH-S) were carried out (LDH release, apoptosis detection, DNA damage, and nitric oxide synthesis). The decrease in particles size, from 1.2 μm to 90 nm, only caused a slight increase in structural defects (disorder of the hematite phase and the presence of surface ferrous ions) without enhancing surface reactivity or cellular responses in the concentration range between 20 and 100 μg cm⁻².

Assessing the in vitro toxicity of the lunar dust environment using respiratory cells exposed to Al(2)O(3) or SiO(2) fine dust particles

Prior chemical and physical analysis of lunar soil suggests a composition of dust particles that may contribute to the development of acute and chronic respiratory disorders. In this study, fine Al(2)O(3) (0.7 μm) and fine SiO(2) (mean 1.6 μm) were used to assess the cellular uptake and cellular toxicity of lunar dust particle analogs. Respiratory cells, murine alveolar macrophages (RAW 264.7) and human type II epithelial (A549), were cultured as the in vitro model system. The phagocytic activity of both cell types using ultrafine (0.1 μm) and fine (0.5 μm) fluorescent polystyrene beads was determined. Following a 6-h exposure, RAW 264.7 cells had extended pseudopods with beads localized in the cytoplasmic region of cells. After 24 h, the macrophage cells were rounded and clumped and lacked pseudopods, which suggest impairment of phagocytosis. A549 cells did not contain beads, and after 24 h, the majority of the beads appeared to primarily coat the surface of the cells. Next, we investigated the cellular response to fine SiO(2) and Al(2)O(3) (up to 5 mg/ml). RAW 264.7 cells exposed to 1.0 mg/ml of fine SiO(2) for 6 h demonstrated pseudopods, cellular damage, apoptosis, and necrosis. A549 cells showed slight toxicity when exposed to fine SiO(2) for the same time and dose. A549 cells had particles clustered on the surface of the cells. Only a higher dose (5.0 mg/ml) of fine SiO(2) resulted in a significant cytotoxicity to A549 cells. Most importantly, both cell types showed minimal cytotoxicity following exposure to fine Al(2)O(3). Overall, this study suggests differential cellular toxicity associated with exposure to fine mineral dust particles.

Soluble iron modulates iron oxide particle-induced inflammatory responses via prostaglandin E(2 )synthesis: In vitro and in vivo studies

Background

Ambient particulate matter (PM)-associated metals have been shown to play an important role in cardiopulmonary health outcomes. To study the modulation of PM-induced inflammation by leached off metals, we investigated intracellular solubility of radio-labeled iron oxide (⁵⁹Fe₂O₃) particles of 0.5 and 1.5 μm geometric mean diameter. Fe₂O₃ particles were examined for the induction of the release of interleukin 6 (IL-6) as pro-inflammatory and prostaglandin E₂ (PGE₂) as anti-inflammatory markers in cultured alveolar macrophages (AM) from Wistar Kyoto (WKY) rats. In addition, we exposed male WKY rats to monodispersed Fe₂O₃ particles by intratracheal instillation (1.3 or 4.0 mg/kg body weight) to examine in vivo inflammation.

Results

Particles of both sizes are insoluble extracellularly in the media but moderately soluble in AM with an intracellular dissolution rate of 0.0037 ± 0.0014 d^-1 for 0.5 μm and 0.0016 ± 0.0012 d^-1 for 1.5 μm ⁵⁹Fe₂O₃ particles. AM exposed in vitro to 1.5 μm particles (10 μg/mL) for 24 h increased IL-6 release (1.8-fold; p < 0.05) and also PGE₂ synthesis (1.9-fold; p < 0.01). By contrast, 0.5 μm particles did not enhance IL-6 release but strongly increased PGE₂ synthesis (2.5-fold, p < 0.005). Inhibition of PGE₂ synthesis by indomethacin caused a pro-inflammatory phenotype as noted by increased IL-6 release from AM exposed to 0.5 μm particles (up to 3-fold; p < 0.005). In the rat lungs, 1.5 but not 0.5 μm particles (4.0 mg/kg) induced neutrophil influx and increased vascular permeability.

Conclusions

Fe₂O₃ particle-induced neutrophilic inflammatory response in vivo and pro-inflammatory cytokine release in vitro might be modulated by intracellular soluble iron via PGE₂ synthesis. The suppressive effect of intracellular released soluble iron on particle-induced inflammation has implications on how ambient PM-associated but soluble metals influence pulmonary toxicity of ambient PM.

Targeted Removal of Bioavailable Metal as a Detoxification Strategy for Carbon Nanotubes

There is substantial evidence for toxicity and/or carcinogenicity upon inhalation of pure transition metals in fine particulate form. Carbon nanotube catalyst residues may trigger similar metal-mediated toxicity, but only if the metal is bioavailable and not fully encapsulated within fluid-protective carbon shells. Recent studies have documented the presence of bioavailable iron and nickel in a variety of commercial as-produced and vendor "purified" nanotubes, and the present article examines techniques to avoid or remove this bioavailable metal. First, data are presented on the mechanisms potentially responsible for free metal in "purified" samples, including kinetic limitations during metal dissolution, the re-deposition or adsorption of metal on nanotube outer surfaces, and carbon shell damage during last-step oxidation or one-pot purification. Optimized acid treatment protocols are presented for targeting the free metal, considering the effects of acid strength, composition, time, and conditions for post-treatment water washing. Finally, after optimized acid treatment, it is shown that the remaining, non-bioavailable (encapsulated) metal persists in a stable and biologically unavailable form up to two months in an in vitro biopersistence assay, suggesting that simple removal of bioavailable (free) metal is a promising strategy for reducing nanotube health risks.

HFE Genotype, Particulate Air Pollution, and Heart Rate Variability

Background— Particulate air pollution has been associated with cardiovascular mortality and morbidity. Transition metals such as iron bound to the particles may be responsible for those associations. The protein product of the hemochromatosis ( HFE ) gene modulates uptake of iron and divalent cations from pulmonary sources and reduces their toxicity. Two HFE polymorphisms (C282Y and H63D) associated with increased iron uptake may modify the effect of metal-rich particles on the cardiovascular system.

Methods and Results— We investigated the association between particulate matter ≤2.5 μm in aerodynamic diameter and heart rate variability in 518 older men from the Normative Aging Study who were examined between November 2000 and December 2004. Linear regression models were fit to evaluate interactions between HFE genotype and particulate matter ≤2.5 μm in aerodynamic diameter in relation to heart rate variability, controlling for potential confounders. A 10-μg/m 3 increase in particulate matter ≤2.5 μm in aerodynamic diameter during the 48 hours before heart rate variability measurement was associated with a 31.7% (95% CI, 10.3% to 48.1%) decrease in the high-frequency component of heart rate variability in persons with the wild-type genotype, whereas no relationship in the high-frequency component was observed in persons with either HFE variant. The difference in effect of particulate matter ≤2.5 μm in aerodynamic diameter on the high-frequency component between persons with and without HFE variants was significant ( P for interaction=0.02).

Conclusions— The effect of particles on cardiac autonomic function was shielded in subjects with at least 1 copy of an HFE variant compared with wild-type subjects. Transition metals, including iron, bound to ambient particles and the related oxidative stress may play an important role in cardiac toxicity of particles.

Air pollution and lung function among susceptible adult subjects: a panel study

BACKGROUND

Adverse health effects at relatively low levels of ambient air pollution have consistently been reported in the last years. We conducted a time-series panel study of subjects with chronic obstructive pulmonary disease (COPD), asthma, and ischemic heart disease (IHD) to evaluate whether daily levels of air pollutants have a measurable impact on the lung function of adult subjects with pre-existing lung or heart diseases.

METHODS

Twenty-nine patients with COPD, asthma, or IHD underwent repeated lung function tests by supervised spirometry in two one-month surveys. Daily samples of coarse (PM10-2.5) and fine (PM2.5) particulate matter were collected by means of dichotomous samplers, and the dust was gravimetrically analyzed. The particulate content of selected metals (cadmium, chrome, iron, nickel, lead, platinum, vanadium, and zinc) was determined by atomic absorption spectrometry. Ambient concentrations of nitrogen dioxide (NO2), carbon monoxide (CO), ozone (O3), and sulphur dioxide (SO2) were obtained from the regional air-quality monitoring network. The relationships between concentrations of air pollutants and lung function parameters were analyzed by generalized estimating equations (GEE) for panel data.

RESULTS

Decrements in lung function indices (FVC and/or FEV1) associated with increasing concentrations of PM2.5, NO2 and some metals (especially zinc and iron) were observed in COPD cases. Among the asthmatics, NO2 was associated with a decrease in FEV1. No association between average ambient concentrations of any air pollutant and lung function was observed among IHD cases.

CONCLUSION

This study suggests that the short-term negative impact of exposure to air pollutants on respiratory volume and flow is limited to individuals with already impaired respiratory function. The fine fraction of ambient PM seems responsible for the observed effects among COPD cases, with zinc and iron having a potential role via oxidative stress. The respiratory function of the relatively young and mild asthmatics included in this study seems to worsen when ambient levels of NO2 increase.

Abrasive blasting agents: designing studies to evaluate relative risk

Workers exposed to respirable crystalline silica used in abrasive blasting are at increased risk of developing a debilitating and often fatal fibrotic lung disease called silicosis. The National Institute for Occupational Safety and Health (NIOSH) recommends that silica sand be prohibited as abrasive blasting material and that less hazardous materials be used in blasting operations. However, data are needed on the relative risks associated with exposure to abrasive blasting materials other than silica. NIOSH has completed acute studies in rats (Hubbs et al., 2001; Porter et al., 2002). To provide dose-response data applicable to making recommendation for occupational exposure limits, NIOSH has collaborated with the National Toxicology Program (NTP) to design longer term studies with silica substitutes. For risk assessment purposes, selected doses will include concentrations that are relevant to human exposures. Rat lung burdens achieved should be comparable to those estimated in humans with working lifetime exposures, even if this results in "overloading" doses in rats. To quantify both dose and response, retained particle burdens in the lungs and lung-associated lymph nodes will be measured, as well as biochemical and pathological indices of pulmonary response. This design will facilitate assessment of the pulmonary fibrogenic potential of inhaled abrasive blasting agents at occupationally relevant concentrations.

Acute pulmonary and hematological effects of two types of particle surrogates are influenced by their elemental composition

Several epidemiological studies have consistently demonstrated significant associations between ambient levels of particulate matter and lung injury and cardiovascular events with increased morbidity and mortality. Particle surrogates (PS), such as residual oil fly ash (ROFA), have been widely used in experimental studies aimed at characterizing the mechanisms of particle toxicity. Since PS composition varies depending on its source, studies with different types of PS may provide clues about the relative toxicity of the components generated by high-temperature combustion process. In this work, we have studied the effects of nasal instillation of increasing doses of different PS in mice: saline, carbon, and two types of particle surrogates. PS type A (PSA) was the ROFA collected from the waste incinerator of our university hospital; PS type B (PSB) was collected from the electrostatic precipitator of a large steel company and thus had an elevated metal content. After 24h, we analyzed hematological parameters, fibrinogen, bronchoalveolar lavage, bone marrow, and pulmonary histology. Nasal instillation of the two types of PS-induced leucopenia. PSB elicited a greater elevation of plasma fibrinogen levels. Bone marrow and pulmonary inflammatory changes were more intense for PSA. We concluded that the PS composition modulates acute inflammatory changes more significantly than the mass for these two types of PS.

Effects of sham air and cigarette smoke on A549 lung cells: implications for iron-mediated oxidative damage

Inhalation of airborne pollution particles that contain iron can result in a variety of detrimental changes to lung cells and tissues. The lung iron burden can be substantially increased by exposure to cigarette smoke, and cigarette smoke contains iron particulates, as well as several environmental toxins, that could influence intracellular iron status. We are interested in the effects of environmental contaminants on intracellular iron metabolism. We initiated our studies using lung A549 type II epithelial cells as a model, and we evaluated the effects of iron dose and smoke treatment on several parameters of intracellular iron metabolism. We show that iron at a physiological dose stimulates ferritin synthesis without altering the transferrin receptor (TfR) mRNA levels of these cells. This is mediated primarily by a reduction of iron regulatory protein 2. Higher doses of iron reduce iron regulatory protein-1 binding activity and are accompanied by a reduction in TfR mRNA. Thus, for A549 cells, different mechanisms influencing IRP-IRE interaction allow ferritin translation in the presence of TfR mRNA to provide for iron needs and yet prevent excessive iron uptake. More importantly, we report that smoke treatment diminishes ferritin levels and increases TfR mRNA of A549 cells. Ferritin serves as a cytoprotective agent against oxidative stress. These data suggest that exposure of lung cells to low levels of smoke as are present in environmental pollutants could result in reduced cytoprotection by ferritin at a time when iron uptake is sustained, thus enhancing the possibility of lung damage by iron-mediated oxidative stress.

Multiple modes of responses to air pollution particulate materials in A549 alveolar type II cells

Exposure to components of air pollution may cause adverse effects on lung cellular and organ functions through several mechanisms. Cell death, altered gene expression including production of cytokines, and modifications of normal cellular processes are possible outcomes that may be independent or coupled. To assess the effects of materials representative of a variety of particulate components of air pollution on lung epithelium, a human cell line of type II origin (A549 cells) was exposed to these materials in vitro. Materials tested included carbon black (CB), diesel soot from two sources (DS), residual oil fly ash (ROFA), Ottowa Ambient Air particulate (OAA), silicon dioxide (SiO2), and nickel subsulfide (Ni3S2). Endpoints included loss of adherence measured by crystal violet staining (CV), lactate dehydrogenase release (LDH), release of interleukin-8 (IL-8) measured by ELISA, and alkaline phosphatase activity in the cells (APc) and released into the supernatant (APS). Nuclear morphology was also examined. SiO2 and Ni3S2 both caused dose-dependent acute toxicity as assessed by LDH and CV, and caused alterations in nuclear morphology consistent with apoptosis. However, much more IL-8 was released into the tissue culture supernatant by SiO2 at the same levels of cytotoxicity than by Ni3S2. Neither of these acutely toxic materials increased APc or APS, but the less cytotoxic materials caused very significant release of AP in the order OAA > DS > ROFA >> SiO2 = Ni3S2. OAA and, to a lesser extent, DS caused increases in mitotic fraction and increased CV staining, consistent with stimulation of proliferation. These results suggest multiple modes of responses to toxic materials and imply that a toxicological screening process should address these and possibly other endpoints.

Pulmonary responses of acute exposure to ultrafine iron particles in healthy adult rats

As critical constituents of ambient particulate matter, transition metals such as iron may play an important role in health outcomes associated with air pollution. The purpose of this study was to determine the respiratory effects of inhaled ultrafine iron particles in rats. Sprague Dawley rats 10-12 weeks of age were exposed by inhalation to iron particles (57 and 90 microg/m(3), respectively) or filtered air (FA) for 6 h/day for 3 days. The median diameter of particles generated was 72 nm. Exposure to iron particles at a concentration of 90 microg/m(3) resulted in a significant decrease in total antioxidant power along with a significant induction in ferritin expression, GST activity, and IL-1beta levels in lungs compared with lungs of the FA control or of animals exposed to iron particles at 57 microg/m(3). NFkappaB-DNA binding activity was elevated 1.3-fold compared with that of control animals following exposure to 90 microg/m(3) of iron, but this change was not statistically significant. We concluded that inhalation of iron particles leads to oxidative stress associated with a proinflammatory response in a dose-dependent manner. The activation of NFkappaB may be involved in iron-induced respiratory responses, but further studies are merited.

Oxidative stress and NFkappaB activation in the lungs of rats: a synergistic interaction between soot and iron particles

Particulate matter (PM) has been associated with a variety of adverse health effects primarily involving the cardiopulmonary system. However, the precise biological mechanisms to explain how exposure to PM exacerbates or directly causes adverse effects are unknown. Particles of varying composition may play a critical role in these effects. To study such a phenomenon, a simple, laminar diffusion flame was used to generate aerosols of soot and iron particles in the ultrafine size range. Exposures of healthy adult rats were for 6 h/day for 3 days. Conditions used included exposure to soot only, iron only, or a combination of soot and iron. We found animals exposed to soot particles at 250 microg/m3 had no adverse respiratory effects. Exposure to iron alone at a concentration of 57 microg/m3 also had no respiratory effects. However, the addition of 45 microg/m3 of iron to soot with a combined total mass concentration of 250 microg/m3 demonstrated significant pulmonary ferritin induction, oxidative stress, elevation of IL-1beta, and cytochrome P450s, as well as activation of NFkappaB. These findings suggest that a synergistic interaction between soot and iron particles account for biological responses not found with exposure to iron alone or to soot alone.

Capsaicinoids cause inflammation and epithelial cell death through activation of vanilloid receptors

Capsaicinoids, found in less-than-lethal self-defense weapons, have been associated with respiratory failure and death in exposed animals and people. The studies described herein provide evidence for acute respiratory inflammation and damage to epithelial cells in experimental animals, and provide precise molecular mechanisms that mediate these effects using human bronchiolar and alveolar epithelial cells. Inhalation exposure of rats to pepper sprays (capsaicinoids) produced acute inflammation and damage to nasal, tracheal, bronchiolar, and alveolar cells in a dose-related manner. In vitro cytotoxicity assays demonstrated that cultured human lung cells (BEAS-2B and A549) were more susceptible to necrotic cell death than liver (HepG2) cells. Transcription of the human vanilloid receptor type-1, VR1 or TRPV1, was demonstrated by RT-PCR in all of these cells, and the relative transcript levels were correlated to cellular susceptibility. TRPV1 receptor activation was presumably responsible for cellular cytotoxicity, but prototypical functional antagonists of this receptor were cytotoxic themselves, and did not ameliorate capsaicinoid-induced damage. Conversely, the TRPV1 antagonist capsazepine, as well as calcium chelation by EGTA ablated cytokine (IL-6) production after capsaicin exposure. To address these seemingly contradictory results, recombinant human TRPV1 was cloned and overexpressed in BEAS-2B cells. These cells exhibited dramatically increased cellular susceptibility to capsaicinoids, measured using IL-6 production and cytotoxicity, and an apoptotic mechanism of cell death. Surprisingly, the cytotoxic effects of capsaicin in TRPV1 overexpressing cells were also not inhibited by TRPV1 antagonists or by treatments that modified extracellular calcium. Thus, capsaicin interacted with TRPV1 expressed by BEAS-2B and other airway epithelial cells to cause the calcium-dependent production of cytokines and, conversely, calcium-independent cell death. These results have demonstrated that capsaicinoids contained in pepper spray products produce airway inflammation and cause respiratory epithelial cell death. The mechanisms of these cellular responses to capsaicinoids appear to proceed via distinct cellular pathways, but both pathways are initiated by TRPV1.

Comparative pulmonary toxicity of blasting sand and five substitute abrasive blasting agents

Blasting sand is used for abrasive blasting, but its inhalation is associated with pulmonary inflammation and fibrosis. Consequently, safer substitute materials for blasting sand are needed. In a previous study from this laboratory, the comparative pulmonary toxicity of five abrasive blasting substitutes and blasting sand was reported. In this study, the pulmonary toxicity of blasting sand was compared to five additional abrasive blasting substitutes: steel grit, copper slag, nickel slag, crushed glass, and olivine. Exposed rats received by intratracheal instillation 10 mg of respirable-size particles of blasting sand or an abrasive blasting substitute, while controls were instilled with vehicle. Pulmonary inflammation, damage, and fibrosis were examined 28 d postexposure. Pulmonary inflammation was monitored by determining bronchoalveolar lavage polymorphonuclear cell counts and alveolar macrophage activation by chemiluminescence. Pulmonary damage was assessed by acellular bronchoalveolar (BAL) fluid serum albumin concentrations and lactate dehydrogenase activities. Histological examination of lung tissue samples was made to assess the severity and distribution of pulmonary fibrosis, alveolitis, and alveolar epithelial cell hypertrophy and hyperplasia. In comparison to blasting sand, olivine exposed rats had higher levels of pulmonary inflammation and damage with a similar level of fibrosis. Steel grit-exposed rats had lower levels of pulmonary inflammation and damage, and did not develop fibrosis. However, steel grit-exposed rats had a level of epithelial cell hypertrophy and hyperplasia similar to blasting sand. The other abrasive blasting substitutes gave a mixed profile of toxicity. The data demonstrate that steel grit produced less acute pulmonary toxicity than blasting sand or any of the other abrasive blasting substitutes. Notwithstanding, the data also suggest that chronic exposure to steel grit may pose a health risk due to its effects on epithelial cell proliferation in the lung.

Modification of the proteinase/anti-proteinase balance in the respiratory tract of Sprague-Dawley rats after single intratracheal instillation of benzo[A]pyrene-coated onto Fe(2)O(3) particles

Available data suggest that repeated concurrent exposure to haematite (Fe(2)O(3)) and benzo[A]pyrene (B[A]P) results in a decreased latency and an increased incidence of lung tumours in rodents compared to exposure to B[A]P alone. Moreover, the reactive oxygen species (ROS) formed by the lung cells themselves and/or by activated inflammatory cells may possibly contribute to the development of pulmonary disorders such as cancer formation. In order to investigate the precise role of iron in the injury induced by B[A]P-coated onto Fe(2)O(3) particles, we tend to address the hypothesis that Fe(2)O(3) and B[A]P, alone or in association, can induce oxidative stress conditions (malondialdehyde) and/or inflammatory reactions (interleukin-6) and thereby disrupt the proteinase/anti-proteinase balance (cathepsins B and L, polynuclear neutrophil (PNN) elastase, alpha-1 proteinase inhibitor (alpha(1)PI) and its inhibitory capacity) in the rat respiratory tract. Thus, Fe(2)O(3) or B[A]P-coated onto Fe(2)O(3) particles produce oxidative stress conditions through not only iron-catalysed oxidative reactions but also inflammatory processes. However, B[A]P initiates only inflammatory responses. These pollutants generate increased levels of proteases and decrease the concentrations of free alpha(1)PI. There is also a clear relationship between the partial inactivation of alpha(1)PI and the occurrence of ROS after exposure to Fe(2)O(3), alone or as a carrier of B[A]P. Hence, the proteinase/anti-proteinase balance might be more disrupted by Fe(2)O(3) or B[A]P-coated onto Fe(2)O(3) particles than by B[A]P alone. These results suggest a mechanism that can explain why B[A]P-coated onto Fe(2)O(3) particles are more injurious than B[A]P alone.

The distributed lag between air pollution and daily deaths

Many studies have reported associations between air pollution and daily deaths. Those studies have not consistently specified the lag between exposure and response, although most have found associations that persisted for more than 1 day. A systematic approach to specifying the lag association would allow better comparison across sites and give insight into the nature of the relation. To examine this question, I fit unconstrained and constrained distributed lag relations to the association between daily deaths of persons 65 years of age and older with PM10 in 10 U.S. cities (New Haven, Birmingham, Pittsburgh, Canton, Detroit, Chicago, Minneapolis, Colorado Springs, Spokane, and Seattle) that had daily monitoring for PM10. After control for temperature, humidity, barometric pressure, day of the week, and seasonal patterns, I found evidence in each city that the effect of a single day's exposure to PM10 was manifested across several days. Averaging over the 10 cities, the overall effect of an increase in exposure of 10 microg/m3 on a single day was a 1.4% increase in deaths (95% confidence intervals (CI) = 1.15-1.68) using a quadratic distributed lag model, and a 1.3% increase (95% CI = 1.04-1.56) using an unconstrained distributed lag model. In contrast, constraining the model to assume the effect all occurs in one day resulted in an estimate of only 0.65% (95% CI = 0.49-0.81), indicating that this constraint leads to a substantial underestimate of effect. Combining the estimated effect at each day's lag across the 10 cities showed that the effect was spread over several days and did not reach zero until 5 days after the exposure. Given the distribution of sensitivities likely in the general population, this result is biologically plausible. I also found a protective effect of barometric pressure in all 10 locations.