Derivation of PM10 size-selected human equivalent concentrations of inhaled nickel based on cancer and non-cancer effects on the respiratory tract

Abstract

Nickel (Ni) in ambient air is predominantly present in the form of oxides and sulfates, with the distribution of Ni mass between the fine (particle aerodynamic diameter <?2.5?µm; PM_2.5) and coarser (2.5–10?µm) size-selected aerosol fractions of PM₁₀ dependent on the aerosol's origin. When deriving a long-term health protective reference concentration for Ni in ambient air, the respiratory toxicity and carcinogenicity effects of the predominant Ni compounds in ambient air must be considered. Dosimetric adjustments to account for differences in aerosol particle size and respiratory tract deposition and/or clearance among rats, workers, and the general public were applied to experimentally- and epidemiologically-determined points of departure (PODs) such as no(low)-effect concentrations, for both cancer and non-cancer respiratory effects. This approach resulted in the derivation of threshold-based PM₁₀ size-selected equivalent concentrations (modified PODs) of 0.5?µg Ni/m³ based on workers' cancer effects and 9–11?µg Ni/m³ based on rodent respiratory toxicity effects. Sources of uncertainty in exposure extrapolations are described. These are not reference concentrations; rather the derived PM₁₀ size-selected modified PODs can be used as the starting point for the calculation of ambient air reference concentrations for Ni. The described approach is equally applicable to other particulates.     

Nanoparticles-containing spray can aerosol: characterization,exposure assessment,and generator design

This is the first report demonstrating that a commercially available household consumer product produces nanoparticles in a respirable range. This report describes a method developed to characterize nanoparticles that were produced under typical exposure conditions when using a consumer spray product. A well-controlled indoor environment was simulated for conducting spray applications approximating a human exposure scenario. Results indicated that, while aerosol droplets were large with a count median diameter of 22 µm during spraying, the final aerosol contained primarily solid TiO₂ particles with a diameter of 75?nm. This size reduction was due to the surface deposition of the droplets and the rapid evaporation of the aerosol propellant. In the breathing zone, the aerosol, containing primarily individual particles (>90%), had a mass concentration of 3.4?mg/m³, or 1.6?×?10⁵ particles/cm³, with a nanoparticle fraction limited to 170 µg/m³, or 1.2?×?10⁵ particles/cm³. The results were used to estimate the pulmonary dose in an average human (0.075 µg TiO₂ per m² alveolar epithelium per minute) and rat (0.03 µg TiO₂) and, consequently, this information was used to design an inhalation exposure system. The system consisted of a computer-controlled solenoid ‘‘finger’’ for generating constant concentrations of spray can aerosols inside a chamber. Test results demonstrated great similarity between the solenoid ‘‘finger’’-dispersed aerosol compared to human-generated aerosol. Future investigations will include an inhalation study to obtain information on dose–response relationships in rats and to use it to establish a No Effect Exposure Level for setting guidelines for this consumer product.     

Deposition, retention, and biological fate of inhaled benzo(a)pyrene adsorbed onto ultrafine particles and as a pure aerosol

The effect of ultrafine, airborne, carrier particles on the deposition, retention, and biological fate of inhaled polycyclic aromatic hydrocarbons (PAHs) was studied. Using a radiolabeled model PAH, [³H]benzo(a)pyrene ([³H]BaP), Fischer-344 rats were exposed by nose-only inhalation (30 min) to this compound, as a coating (15% by mass) on insoluble ⁶⁷Ga₂O₃ particles or as a pure aerosol. These aerosols were produced by vapor condensation methods in a dynamic aerosol generation system. The concentrations of [³H]BaP in the coated and homogeneous aerosols were 0.6 and 1.0 μg/liter of air, respectively, while the mass median diameter of both these aerosols was approximately 0.1 μm. Pulmonary retention of ³H radioactivity was longer in animals exposed to the [³H]BaP coated on the ⁶⁷Ga₂O₃ particles. The time required to clear 90% of the initial lung burden of ⁶⁷Ga₂O₃-associated ³H radioactivity detected 30 min postexposure was approximately 1 day as compared to 4 hr for animals exposed to the pure [³H]BaP aerosol. Tracheal clearance of 90% of the ⁶⁷Ga₂O₃-associated ³H radioactivity (as a fraction of the amount detected 30 min postexposure) required 1 day, while only 1.5 hr were required to clear the same percentage of ³H radioactivity from the tracheas of rats exposed to the pure [³H]BaP aerosol. The rates of clearance of this ³H material to other tissues suggested that a substantial amount of the [³H]BaP coated on ⁶⁷Ga₂O₃ was cleared from lungs by mucociliary clearance and subsequent ingestion, whereas the majority of the pure [³H]BaP aerosol was cleared by direct absorption into blood. In both cases, the ultimate fate of the majority of the [³H]BaP and its metabolites was excretion in feces. However, clearance of the ⁶⁷Ga₂O₃-associated [³H]BaP by ingestion may have been the cause for the higher levels and longer retention times of ³H radioactivity in stomach, liver, and kidneys when compared to the levels found in these same tissues from animals exposed to the pure [³H]BaP aerosol. Thus, particle association of BaP not only increased the respiratory tract retention of this PAH, but also increased the dose of this compound and its metabolites to stomach, liver, and kidneys.     

PULMONARY EFFECTS OF ULTRAFINE AND FINE AMMONIUM SALTS AEROSOLS IN HEALTHY AND MONOCROTALINE-TREATED RATS FOLLOWING SHORT-TERM EXPOSURE

In the present study the effects of a 3-day inhalation exposure to model compounds for ambient particulate matter were investigated: ammonium bisulfate, ammonium ferrosulfate, and ammonium nitrate, all components of the secondary aerosol fraction of ambient particulate matter (PM), and carbon black (CB, model aerosol for primary PM). The objective of this study was to test the hypothesis that secondary model aerosols exert acute pulmonary adverse effects in rats, and that rats with pulmonary hypertension (PH), induced by monocrotaline (MCT), are more sensitive to these components than normal healthy animals. An additional aim was to test the hypothesis that fine particles exert more effects than ultrafines. Healthy and PH rats were exposed to ultrafine (mass median diameter [MMD] ≈ 0.07-0.10 µm; 4 × 10⁵ particles/cm³) and fine (MMD ≈ 0.57-0.64 µm; 9 × 10 3 particles/cm 3) ammonium aerosols during 4 h/day for 3 consecutive days. The mean mass concentrations ranged from 70 to 420 µg/m 3, respectively, for ultrafine ammonium bisulfate, nitrate, and ferrosulfate and from 275 to 410 µg/m 3 for fine-mode aerosols. In an additional experiment, simultaneous exposure to a fine CB aerosol (0.6 µm; 2-9 mg/m 3) and ammonium nitrate (0.4-18 mg/m 3) was performed. Bronchoalveolar lavage fluid (BALF) analysis and histopathological examination were performed on animals sacrificed 1 day after the last exposure. Histopathology of the lungs did not reveal test atmosphere-related abnormalities in either healthy or PH rats exposed to the ammonium salts, or to a combination of CB + nitrate. Alveolar macrophages in rats exposed to CB only revealed the presence of black material in their cytoplasm. There were no signs of cytotoxicity due to the aerosol exposures (as measured with lactate dehydrogenase [LDH], protein, and albumin contents in BALF). Macrophages were not activated after MCT treatment or the test atmospheres, since no changes were observed in N -acetyl glucosaminidase (NAG). Cell differentiation profiles were inconsistent, partly caused by an already present infection with Haemophilus sp. However, we believe that the test atmospheres did not affect cell differentiation or total cell counts. The results show that at exposure levels of ammonium salts at least one order of magnitude higher than ambient levels, marked adverse health effects were absent in both healthy and PH rats.     

Outdoor wood furnaces create significant indoor particulate pollution in neighboring homes

Abstract

Context: The use of outdoor wood furnaces (OWFs) is common in many parts of the United States. Little published information exists on the concentrations of outdoor and indoor fine particulates found near OWFs.

Objective: To compare PM_2.5 (cts) and PM_0.5 (cts) particle concentrations inside four Connecticut homes located 30.5–259?m from OWFs, and inside six Connecticut control homes located more than 2?km from the nearest OWF.

Materials and methods: PM_2.5 (cts) and PM_0.5 (cts) measurements were made with a Dylos light-scattering particulate counter.

Results: Mean PM_2.5 (cts) concentrations were 4.21 times as great in the four OWF exposed homes than the six control homes (0.302?×?10⁶ counts/m³ versus 0.0718 counts?×?10⁶/m³ p?<?0.001). The mean PM_2.5 (cts) concentrations inside the four OWF exposed homes roughly corresponds to a mass PM_2.5 of 37?µg/m³, which is above the US EPA 24-h PM_2.5 limit of 35?µg/m³. Mean PM_0.5 (cts) concentrations were 3.44 times as great in the four OWF exposed homes than in the six control homes (0.657 versus 0.191?×?10⁶/m³ p?<?0.001). Mean PM_2.5 (cts) and PM_0.5 (cts) concentrations were significantly higher in the house 259?m from an OWF as compared with the mean of the six control homes.

Conclusion: Existing regulations, such as the present Connecticut law requiring a 61 meter distance between an OWF and neighboring homes, are not adequate to protect the health of neighboring residents.     

Respiratory symptoms,lung function decrement and chronic obstructive pulmonary disease in pre-menopausal Indian women exposed to biomass smoke

Abstract

Background: The impact of chronic exposure to smoke from biomass burning on respiratory health has been examined.

Methods: Six-hundred and eighty-one non-smoking women (median age 35 years) from eastern India who cook exclusively with biomass (wood, dung and crop residues) and 438 age-matched women from similar neighborhood who cook with liquefied petroleum gas (LPG) were examined. Pulmonary function test was done by spirometry. The concentrations of particulate matter having diameter of < 10?µm (PM₁₀) and < 2.5?µm (PM_2.5) in indoor air was measured by real-time aerosol monitor.

Results: Compared with LPG users, biomass users had greater prevalence of upper (50.9 versus 28.5%) and lower respiratory symptoms (71.8 versus 30.8%) and dyspnea (58.4 versus 19.9%). They showed reduction in all parameters measured by spirometer especially in mid-expiratory volume. PM₁₀ and PM_2.5 concentration in biomass using kitchen were 2–3-times more than LPG-using kitchen, and the decline in spirometry values was positively associated PM₁₀ and PM_2.5 levels in indoor air after controlling education, family income and kitchen location as potential confounders. Overall, 29.7% of biomass users and 16.4% of LPG users had deficient lung function, and restrictive type of deficiency was predominant. Chronic obstructive pulmonary disease (COPD) was diagnosed in 4.6% of biomass and 0.9% of LPG users. Women who predominantly used dung cake and did not possess separate kitchen had poorer lung function.

Conclusion: Cumulative exposure to biomass smoke causes lung function decrement and facilitates COPD development even in non-smoking and relatively young pre-menopausal women.     

Inhalation toxicology of sodium sulfite aerosols in rats

Rats were exposed to well-characterized aerosols of sodium sulfite, at levels ranging from 0.1 to about 15 mg/m³ and particle sizes of about 1 μm (mass median aerodynamic diameter). The responses of rats to breathing these aerosols for 3 days were evaluated by measurements of glycoprotein secretion rates by cultured tracheal explants from these rats, by measurement of protein, DNA, and RNA levels of lung homogenates prepared from these rats, and by quantitation of wet to dry weight ratios of right apical lung lobes from these rats. Increased rates of glycoprotein secretion were observed for tracheae from rats exposed to 5 or to 15 mg/m³ of Na₂SO₃ aerosol, and increased wet to dry weight ratios of right apical lobes were also observed after exposure to these levels, as well as after exposure to 1 mg/m³ of Na₂SO₃ aerosol. Control experiments involving exposure to a sulfate (Na₂SO₄) aerosol at 15 mg/m³ indicated that the observed effects were indeed due to exposure to the sulfite moiety. Exposure to aerosols of sodium hydroxymethane sulfonate (the product of addition of formaldehyde to sodium sulfite) aerosols (5 mg/m³) elicited less response in these assays than did exposure to sodium sulfite aerosol at the same concentration. We conclude that exposure of rats to well-characterized 1-μm aerosols of sodium sulfite at concentrations equivalent to amounts of SO₂ of about 0.2 – 2.7 ppm results in responses of the rats that may be conveniently evaluated when sensitive enough toxicological indexes are quantitated.     

Multi-walled carbon nanotubes: sampling criteria and aerosol characterization

This study intends to develop protocols for sampling and characterizing multi-walled carbon nanotube (MWCNT) aerosols in workplaces or during inhalation studies. Manufactured dry powder containing MWCNT’s, combined with soot and metal catalysts, form complex morphologies and diverse shapes. The aerosols, examined in this study, were produced using an acoustical generator. Representative samples were collected from an exposure chamber using filters and a cascade impactor for microscopic and gravimetric analyses. Results from filters showed that a density of 0.008–0.10 particles per µm² filter surface provided adequate samples for particle counting and sizing. Microscopic counting indicated that MWCNT’s, resuspended at a concentration of 10?mg/m³, contained 2.7?×?10⁴ particles/cm³. Each particle structure contained an average of 18 nanotubes, resulting in a total of 4.9?×?10⁵ nanotubes/cm³. In addition, fibrous particles within the aerosol had a count median length of 3.04 µm and a width of 100.3?nm, while the isometric particles had a count median diameter of 0.90 µm. A combination of impactor and microscopic measurements established that the mass median aerodynamic diameter of the mixture was 1.5 µm. It was also determined that the mean effective density of well-defined isometric particles was between 0.71 and 0.88?g/cm³, and the mean shape factor of individual nanotubes was between 1.94 and 2.71. The information obtained from this study can be used for designing animal inhalation exposure studies and adopted as guidance for sampling and characterizing MWCNT aerosols in workplaces. The measurement scheme should be relevant for any carbon nanotube aerosol.     

Plasma nitrite is an indicator of acute changes in ambient air pollutant concentrations

Abstract

Context: Endothelial dysfunction has been suggested as a potential mechanism by which ambient air pollution may cause acute cardiovascular events. Recently, plasma nitrite has been developed as a marker of endothelial dysfunction.

Objectives: We examined the changes in plasma nitrite concentration associated with increases in ambient air pollutant concentrations in the previous 7 d.

Materials and methods: We linked up to three measurements of plasma nitrite concentrations obtained from 49 students to 24-h average concentrations of five criteria air pollutants [particle mass?<?2.5?µm in aerodynamic diameter (PM_2.5), carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and ozone (O₃)] measured at two monitoring sites closest to Rutgers University campus (6–15 miles) in New Jersey during the years 2006–2009. We examined the change in plasma nitrite associated with each interquartile-range (IQR) increase in pollutant concentration in the previous 24?h and six preceding 24-?h periods, using linear mixed models.

Results: IQR increases in mean PM_2.5 (7.0?µg/m³) and CO (161.7 parts per billion) concentrations in the first 24?h before the plasma nitrite measurement were associated with increased plasma nitrite concentrations (PM_2.5: 15.5 nanomolar; 95% confidence interval (CI): 2.4, 28.5; CO: 15.6 nanomolar; 95% CI: 2.4, 28.9). Increased plasma nitrite associated with IQR increases in O₃ and SO₂ concentrations over longer lags were observed.

Discussion and conclusion: Rapid increases in plasma nitrite following exposure to ambient air pollutants support the hypothesis that ambient air pollution is associated with inducible nitric oxide synthase-mediated systemic inflammation in humans.     

Lead Exposure in Children Living in a Smelter Community in Region Lagunera,Mexico

Industrial growth has created the potential for environmental problems in Mexico, since attention to environmental controls and urban planning has lagged behind the pace of industrialization. The aim of this cross-sectional study was to assess lead exposure in children aged 6-9 yr attending 3 primary schools and living in the vicinity of the largest smelter complex in Mexico. One of the schools is located 650 m distant from a smelter complex that includes a lead smelter (close school); the second is located 1750 m away from the complex and at the side of a heavy traffic road (intermediate school) in Torreón, Coahuila. The third school is located in Gómez Palacio, Durango, 8100 m away from the smelter complex and distant from heavy vehicular traffic or industrial areas (remote school). Lead was measured in air, soil, dust, and well water. Lead in blood (PbB) was determined in 394 children attending the above mentioned schools. Determinations were performed by atomic absorption spectrometry. Diet, socioeconomic status, hygienic habits, and other variables were assessed by questionnaire. Median (range) PbB values were 7.8 µg/dl (3.54-29.61) in the remote school, 21.8 µg/dl (8.37-52.08) in the intermediate school and 27.6 µg/dl (7.37-58.53) in children attending the close school. The percentage of children with PbB &gt;15 µg/dl was 6.8%, 84.9%, and 92.1% respectively. In this order, the geometric means (range) of Pb concentrations in air were 2.5 µg/m³ (1.1-7.5), 5.8 µg/m³ (4.3-8.5), and 6.1 µg/m³ (1.6-14.9). The Pb concentrations in dust from playgrounds areas in the intermediate and close school settings ranged from 1457 to 4162.5 mg/kg. Pb concentrations in drinking water were less than 5 µg/L. Soil and dust ingestion and inhalation appear to be the main routes of exposure. Our results indicate that environmental contamination has resulted in an increased body burden of Pb, suggesting that children living in the vicinity of the smelter complex are at high risk for adverse effects of lead.     

3-Hydroxybenzo(a)pyrene as a biomarker of dermal exposure to benzo(a)pyrene

The aim of this study was to determine the percutaneous absorption flux of BaP (20 μg/cm² in ethanol) and the usefulness of urinary 3-OHBaP as a bio-indicator of dermal exposure to BaP. The percutaneous absorbed dose and absorption flux were estimated by comparison with intravenous administration of BaP (0.01 and 0.05 mg/kg in Cremophor^®) as reference way. A percutaneous absorption flux of 0.37 μg/cm²/h was determined by killing groups of rats, following exposure time of 4.5 and 24 h. [¹⁴C] skin content was 3.1 μg/cm², after 24 h exposure to BaP. Total urinary 3-OHBaP accounted for 0.4% of the real absorbed dose, which was fourfold higher than the percentage of an intravenous dose excreted as 3-OHBaP. This finding reveals that percutaneous absorption of BaP, based on the ratio of urinary excretion of 3-OHBaP following percutaneous exposure compared to percutaneous absorption following intravenous administration of BaP, is overestimated in the rat. In vitro, BaP was intensively metabolised by rat skin. Unchanged BaP and 3-OHBaP in receptor fluid accounted for 50 and 30% of the total radioactivity. This percutaneous first past effect of BaP in rats could, in part, explain the higher urinary excretion ratio of 3-OHBaP compared to the value based on intravenous administration of BaP. Conversely, BaP was largely lower metabolised as 3-OHBaP during percutaneous absorption by humans, so BaP absorption flux should be overestimated to a lesser extent in humans than in rats.     

Comparative study of dissolved and nanoparticulate Ag effects on the life cycle of an estuarine meiobenthic copepod,Amphiascus tenuiremis

Many nanotoxicological studies have assessed the acute toxicity of nanoparticles (NPs) at high exposure concentrations. There is a gap in understanding NP chronic environmental effects at lower exposure concentrations. This study reports life-cycle chronic toxicity of sublethal exposures of polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) relative to dissolved silver nitrate (AgNO₃) for the estuarine meiobenthic copepod, Amphiascus tenuiremis, over a range of environmentally relevant concentrations, i.e., 20, 30, 45, and 75?µg-Ag?L^?1. A concentration-dependent increase in mortality of larval nauplii and juvenile copepodites was observed. In both treatment types, significantly higher mortality was observed at 45 and 75?µg-Ag?L^?1 than in controls. In AgNO₃ exposures, fecundity declined sharply (1.8–7 fold) from 30 to 75?µg Ag?L^?1. In contrast, fecundity was not affected by PVP-AgNPs exposures. A Leslie matrix population-growth model predicted sharply 60–86% of decline in overall population sizes and individual life-stage numbers from 30–75?µg-Ag L^?1 as dissolved AgNO₃. In contrast, no population growth suppressions were predicted for any PVP-AgNPs exposures. Slower release of dissolved Ag from PVP-AgNPs and/or reduced Ag uptake in the nanoform may explain these sharp contrasts in copepod response.     

EVALUATION OF THE HEALTH RISK ASSOCIATED WITH EXPOSURE TO CHLOROFORM IN INDOOR SWIMMING POOLS

The exposure of swimmers to chloroform (CHCl₅) was investigated in indoor swimming pools of the Quebec City region along with the associated carcinogenic risk. Six training sessions involving 52 competition swimmers (11 to 20 yr old) were conducted in 3 different pools, while 12 adult leisure swimmers attended 5 sessions, each held in a different pool. For each session, water and ambient air CHCl₃ concentrations were measured and CHCl₃ levels in alveolar air samples (CHCl₃ALV) collected from swimmers prior to entering the swimming pool premises and after 15, 35, and 60 min of swimming. Mean water concentrations varied from 18 µg/L to 80 µg/L, while those in air ranged from 78 µg/m3 to 329 µg/m3. Multiple linear regression analyses revealed that CHCl₃ALV values in competition swimmers were strongly correlated to ambient air and water levels, and to a lesser degree to the intensity of training. Only ambient air concentration was positively correlated to CHCl₃ALV in the leisure group. Concentrations of CHCl₃ metabo lites bound to hepatic and renal macromolecules, estimated using a physiologically based pharmacokinetic (PBPK) model, were 1.6 and 1.9 times higher for the competition swimmers than for the leisure swimmers, respectively. The highest hepatic concentration predicted in competition swimmers, 0.22 µg CHCl equivalents/kg of tissue, was at least 10,000 times lower than the smallest no observed³effect level for liver tumors in animals. Data indicate that the safety margin is therefore very large, for competitive swimmers as well as for leisure swimmers.     

Changing the dose metric for inhalation toxicity studies: Short-term study in rats with engineered aerosolized amorphous silica nanoparticles

Inhalation toxicity and exposure assessment studies for nonfibrous particulates have traditionally been conducted using particle mass measurements as the preferred dose metric (i.e., mg or μg/m³). However, currently there is a debate regarding the appropriate dose metric for nanoparticle exposure assessment studies in the workplace. The objectives of this study were to characterize aerosol exposures and toxicity in rats of freshly generated amorphous silica (AS) nanoparticles using particle number dose metrics (3.7?×?10⁷ or 1.8?×?10⁸ particles/cm³) for 1- or 3-day exposures. In addition, the role of particle size (d₅₀?=?37 or 83?nm) on pulmonary toxicity and genotoxicity endpoints was assessed at several postexposure time points. A nanoparticle reactor capable of producing, de novo synthesized, aerosolized amorphous silica nanoparticles for inhalation toxicity studies was developed for this study. SiO₂ aerosol nanoparticle synthesis occurred via thermal decomposition of tetraethylorthosilicate (TEOS). The reactor was designed to produce aerosolized nanoparticles at two different particle size ranges, namely d₅₀?=?～30?nm and d₅₀?=?～80?nm; at particle concentrations ranging from 10⁷ to 10⁸ particles/cm³. AS particle aerosol concentrations were consistently generated by the reactor. One- or 3-day aerosol exposures produced no significant pulmonary inflammatory, genotoxic, or adverse lung histopathological effects in rats exposed to very high particle numbers corresponding to a range of mass concentrations (1.8 or 86?mg/m³). Although the present study was a short-term effort, the methodology described herein can be utilized for longer-term inhalation toxicity studies in rats such as 28-day or 90-day studies. The expansion of the concept to subchronic studies is practical, due, in part, to the consistency of the nanoparticle generation method.     

Design of an environmentally controlled rotating chamber for bioaerosol aging studies

Abstract

A chamber was designed and built to study the long-term effects of environmental conditions on air-borne microorganisms. The system consists of a 55.5-L cylindrical chamber, which can rotate at variable speeds on its axis. The chamber is placed within an insulated temperature controlled enclosure which can be either cooled or heated with piezoelectric units. A germicidal light located at the chamber center irradiates at a 360° angle. Access ports are located on the stationary sections on both ends of the chamber. Relative humidity (RH) is controlled by passing the aerosol through meshed tubes surrounded by desiccant. Validation assay indicates that the interior temperature is stable with less than 0.5?°C in variation when set between 18 and 30?°C with the UV light having no effect of temperature during operation. RH levels set at 20%, 50% and 80% varied by 2.2%, 3.3% and 3.3%, respectively, over a 14-h period. The remaining fraction of particles after 18?h of suspension was 8.8% at 1 rotation per minute (rpm) and 2.6% at 0?rpm with the mass median aerodynamic diameter (MMAD) changing from 1.21?±?0.04?µm to 1.30?±?0.02?µm at 1?rpm and from 1.21?±?0.04?µm to 0.91?±?0.01?µm at 0?rpm within the same time period. This chamber can be used to increase the time of particle suspension in an aerosol cloud and control the temperature, RH and UV exposure; the design facilitates stationary sampling to be performed while the chamber is rotating.     

Ovarian disorders in immature rats after postnatal exposure to environmental polycyclic aromatic hydrocarbons

The study investigated the effects of postnatal exposure to polycyclic aromatic hydrocarbons (PAHs) on the development of the rat ovary. Neonates were injected on each postnatal day 1–14 with benzo(a)pyrene (BaP), benz(a)anthracene (BaA) and benzo(k)fluoranthene (BkF) (0.1, 1.0, 5.0 or 10.0 mg kg^?1), ethynylestradiol (EE; 1.0 µg kg^?1) or a vehicle (control group). The rats were killed on day 23. Postnatal exposure to BaP increased the total number of antral follicles in ovaries (P < 0.05) and the number of nonatretic follicles (P < 0.01) as a result of a lower degree of apoptosis of granulosa cells, and the thickness of theca cell layers (P < 0.01). Similar histological findings were observed after BaA administration. Conversely, BkF exposure caused a decrease in the number of antral follicles, but did not alter the other investigated parameters. Degeneration of primordial oocytes after exposure to PAHs was observed only after exposure to BaP. Treatment with BaP at doses of 1.0 and 10.0 mg kg^?1 impaired 28.1 and 60.3% of the primordial follicles, respectively. Substantial alterations in ovarian ERβ expression were detected in the rats; their intensity differed with the type of PAH. Response of the ovaries to EE (three injections of 1.0 µg kg^?1 on postnatal days 20–22) in rats exposed to PAHs was suppressed in contrast to the controls. The study showed that postnatal exposure to BaP, BaA and BkF altered ovarian ERβ expression, disturbed morphological development of the ovaries and caused ovarian dysfunction in immature rats. Copyright © 2011 John Wiley & Sons, Ltd.     

Comparison of Calidria Chrysotile Asbestos to Pure Tremolite: Inhalation Biopersistence and Histopathology Following Short-Term Exposure

The differences between chrysotile asbestos, a serpentine mineral, and amphibole asbestos have been debated extensively. Many studies have shown that chrysotile is cleared from the lung more rapidly than amphibole. In order to quantify the comparative clearance of chrysotile and the amphibole asbestos tremolite, both fibers were evaluated in an inhalation biopersistence study that followed the European Commission recommended guidelines. In addition, the histopathological response in the lung was evaluated following the short-term exposure. This article presents the results of this study through 90 days after cessation of exposure. Following the termination of the study, a subsequent article will provide the complete results through 12 mo after cessation of exposure. In order to quantify the dynamics and rate by which these fibers are removed from the lung, the biopersistence of a sample of commercial grade chrysotile from the Coalinga mine in New Idria, CA, of the type Calidria RG144 and of a long-fiber tremolite were studied. For synthetic vitreous fibers, the biopersistence of the fibers longer than 20 µm has been found to be directly related to their potential to cause disease. This study was designed to determine lung clearance (biopersistence) and the histopathological response. As the long fibers have been shown to have the greatest potential for pathogenicity, the aerosol generation technique was designed to maximize the number of long respirable fibers. The chrysotile samples were specifically chosen to have 200 fibers/cm³ longer than 20 µm in length present in the exposure aerosol. These longer fibers were found to be largely composed of multiple shorter fibrils. The tremolite samples were chosen to have 100 fibers/cm³ longer than 20 µm in length present in the exposure aerosol. Calidria chrysotile fibers clear from the lung more rapidly (T_{1/2, fibers L>20 µm} = 7 h) than any other commercial fiber tested including synthetic vitreous fibers. With such rapidly clearing fibers, the 5-day exposure would not be expected to result in any pathological change in the lung, and the lungs of animals that inhaled Calidria chrysotile showed no sign of inflammation or pathology and were no different than the lungs of those animals that breathed filtered air. Following this 5-day exposure to tremolite, the tremolite fibers once deposited in the lung parenchyma do not clear and almost immediately result in inflammation and a pathological response in the lung. At the first time point examined, 1 day after cessation of exposure, inflammation was observed and granulomas were already formed. By 14 days postexposure these microgranulomas had turned fibrotic, and by 90 days postexposure the severity of the collagen deposits had increased and interstitial fibrosis was observed in one of the rats. These findings provide an important basis for substantiating both kinetically and pathologically the differences between chrysotile and the amphibole tremolite. As Calidria chrysotile has been certified to have no tremolite fiber, the results of the current study together with the results from toxicological and epidemiological studies indicate that this fiber is not associated with lung disease.     

Fine particulate air pollution associated with increased risk of hospital admissions for hypertension in a tropical city,Kaohsiung, Taiwan

The aim of this study was to assess whether a correlation exists between fine particles (PM_2.5) levels and number of hospital admissions for hypertension in Kaohsiung, Taiwan. Hospital admission frequency and ambient air pollution data were obtained for Kaohsiung for 2009–2013. A time-stratified case-crossover method was used to estimate relative risk for hospital admissions, controlling for weather, day of the week, seasonality, and long-term time trends. Odds ratios and 95% confidence intervals were calculated for a 10 µg/m³ increment of PM_2.5 for lags from days 0 to 6. Data showed no significant associations between PM_2.5 levels and number of hypertension-related hospital admissions on warm days (>25°C). However, on cool days (<25°C), a significant positive association was found with frequency of hypertension admissions in the single-pollutant model (without adjusting for other pollutants) with a 10 µg/m³ rise in PM_2.5 on day of admission (lag 0) associated with a 12% increase in number of admissions for hypertension. In the two-pollutant model, the association of PM_2.5 with rate of hypertension hospitalizations remained significant after including SO₂ or O₃ on lag day 0. Data demonstrate that an association between short-term exposure to PM_2.5 and elevated risk of hypertension-related hospital admissions may exist in Kaohsiung, Taiwan, a tropical city.