Personal sampler for nitrogen dioxide

A new type of personal sampler for gases in air, originally reported from this laboratory, has been adapted to measurement of NO2. The sampler depends on the transfer of NO2 by diffusion to a triethanolamine coated collector at the sealed end of a tube; the open end of the tube is exposed to the test environment. The devices are accurate, light, simple to use and have very good shelf life before and after sampling.     

Respiratory effects associated with indoor nitrogen dioxide exposure in children

BACKGROUND: The human health effects of exposure to indoor nitrogen dioxide (NO2) are unclear, and few studies have examined the effects of short-term peak levels of exposure. METHODS: The association between indoor exposure to NO2 and respiratory illness was examined in 388 children aged 6-11 years. The NO2 levels were monitored during winter in 41 classrooms, from four schools with unflued gas heating and four schools with electric heating. Each classroom was monitored daily with 6-hour passive diffusion badge monitors over nine alternate weeks, and with hourly monitors over two of those weeks. Children living in homes with unflued gas appliances were also monitored daily over four evenings during times of gas use. RESULTS: Exposure to NO2 at hourly peak levels of the order of > or = 80 ppb, compared with background levels of 20 ppb, was associated with a significant increase in sore throat, colds and absences from school. An increase in cough with phlegm was marginally significant. Significant dose-response relationships were demonstrated for these four measures with increasing levels of NO2 exposure. CONCLUSIONS: Short-term peak levels of exposure are important to consider in relation to adverse respiratory effects associated with NO2 exposure.     

Combined exposures of human ciliated cells to different concentrations of sulfur dioxide and nitrogen dioxide

In the present study we investigated the influence of two common air pollutants, sulfur dioxide (SO2) and nitrogen dioxide (NO2) on ciliary beat frequency (CBF). Ciliated cells were obtained by nose brush from 12 healthy volunteers and placed on a polycarbonate membrane which was in contact with Ringer's electrolyte solution. This allowed the supply of the cells by capillarity in parallel to the reaction of the pollutants with the cell surfaces. In an exposure chamber the cells were exposed for 30 min. at 37 degrees C either to SO2 (2.5-12.5 ppm) or to NO2 (3.0-15.0 ppm), or to a mixture of NO2 (12.0 ppm) and SO2 (2.5 or 5.0 ppm). CBF was measured by video-interference-microscopy. With SO2 we observed a dose-dependent decrease in CBF with Ringer's solution. 2.5 ppm SO2 caused a 42.8% decrease and 12.5 ppm a decline of approximately 100% (8.10 +/- 0.24 Hz vs. 0.28 +/- 0.20 Hz). In parallel, we observed a decrease in the pH-value from 7.4 to 3.6. 30 min. NO2 exposure (3.0-15.0 ppm) induced a significant dose dependent increase in CBF from 8.4 +/- 0.34 Hz to 9.4 +/- 0.44 Hz. Exposure to a mixture of SO2 and NO2 with Ringer's solution revealed that SO2 exerts a stronger influence on CBF than NO2. Exposure to both pollutants resulted in the same as exposure to SO2 alone. Our findings demonstrate a strong correlation between SO2-modified pH values and CBF. Exposure to a combination of two pollutants revealed the dominant influence of SO2 on CBF while the augmented effect of exposure to NO2 alone might be due to the oxidative potential of this gas.     

Front-door concentrations and personal exposures of Danish children to nitrogen dioxide

The aims of the study were to evaluate the front-door concentration of traffic exhaust fumes as a surrogate for the personal exposure of children and to study factors in the behavior and the environment of children that affect their personal exposure to nitrogen dioxide (NO(2)). The exposure to NO(2) of 103 children living in Copenhagen and 101 children living in rural areas of Denmark was studied by measuring average concentrations over 1 week with diffusive badge samplers placed outside the front door of the home, inside the child's bedroom, and on each child. Detailed information about the activities of the children involving potential exposure to NO(2) was noted in diaries. The results indicated that the front-door concentration of traffic pollution might be used to classify the personal exposure of urban children, although misclassification would be introduced. Multiple regression analysis showed several factors that affected the personal NO(2) exposure of the children independently, including the front-door concentration, the bedroom concentration, time spent outdoors, gas appliances used at home, passive smoking, and burning candles.     

Personal sampling of particles in adults: relation among personal, indoor, and outdoor air concentrations

To investigate the validity of outdoor particulate matter with a 50% cutoff diameter of 10-microm (PM10) concentrations as a measure of exposure in time series studies, the association between personal and outdoor concentrations, within subjects, over time was investigated. Repeated measurements of personal, indoor, and outdoor PM10 were conducted among 37 nonsmoking, 50- to 70-year-old adults, living in Amsterdam, Netherlands, 1994. Regression analyses were conducted for each subject separately, and the distribution of the individual regression and correlation coefficients was investigated. Furthermore, the extent to which differences among personal, indoor, and outdoor concentrations could be explained was studied. The median Pearson's R between personal and outdoor concentrations was 0.50. Excluding days with exposure to environmental tobacco smoke (ETS) improved the correlation to a median R of 0.71. The estimated cross-sectional correlations were lower, 0.34 and 0.50, respectively. Outdoor concentrations (mean, 42 microg/m3) exceeded indoor concentrations (mean, 35 microg/m3) but underestimated personal exposures (mean, 62 microg/m3). The major part of the difference between personal and outdoor concentrations could be attributed to exposure to ETS, living along a busy road, and time spent in a vehicle. The results show a reasonably high correlation between personal and outdoor PM10 within individuals, providing support for the use of ambient PM10 concentrations as a measure of exposure in epidemiologic studies linking the day-to-day variation in particulate matter air pollution to the day-to-day variation in health endpoints such as mortality, hospital admissions, respiratory symptoms, and lung function.     

Pollen and fungal spores indoor and outdoor of mobile homes

A clinical analysis on 127 cases out of 140 cases presenting with fungemia at Fukuoka University Hospital between 1984 and 1994 was done. The number of the positive blood cultures during the same period was 1188 and the rate of fungemia was 11.8%. The rates generally increased in recent years, 9.0% (1984-1986), 10.2% (1987-1989) and 13.6% (1990-1994), but decreased after 1992. C. albicans has shown a tendency to decrease while C. parapsilosis and C. glabrata have increased in recent years thus suggesting the effect of the prevalence of intravenous hyperalimentation (IVH) and azole antifungal agents. Only 3.9% of the fungemia were preceded by bacteremia. In addition to the known risk factors for fungemia such as IVH (89.0%) and the antibacterial agents, H2-receptor antagonists were used in 58.3% of the cases. 14 cases of the fungemia were observed during the prophylactic use of antifungal drugs. Therefore, fungemia should always be kept in mind regarding the differential diagnosis for bacteremia when an indwelling venous catheter is used. The prompt extubation of the catheter in addition to the adjustment of the dosage of antifungal drugs in response to the status of the host defense system are thus considered to be important in the treatment of fungemia.     

Measurements of nitrogen solubility in iron and iron-nickel alloys,using a new temperature gradient method

Usually gas solubility measurements in metals are done isothermally and separately for the solid and liquid states. The knowledge of gas solubility at phase changes, especially in the melting range, is of a predominant interest e.g. for foundrymen or for welders, as defects (segregation, gas pores, inclusions) may occur due to the change of solubility. Therefore, a method has been developed, in which a finely grained sample is exposed to a temperature gradient in a long ceramic tube, until equilibrium with the gas phase with regard to local temperature is reached in all locations. The chilled sample is subdivided into small samples which can be analysed for gas content. The method is demonstrated for the determination of nitrogen solubility in iron and some iron-nickel alloys, where results for the austenite and δ-ferrite phases are presented.     

Comparison of respirable coal mine dust concentrations measured with an MRE and a newly-developed, two-stage impactor sampler

The design and laboratory evaluation of a two-stage aerosol sampler using an impaction plate for removing particles above 10 micron, has been reported. The unit was developed to provide an alternative to the two-stage sampling head used on approved coal mine personal respirable dust samplers. The new device offers the potential of increasing the analytical accuracy of samples, and of providing a device more suitable to the mining community for use in their mandated dust sampling program. This paper describes the underground sampling program conducted to establish the factor for converting respirable dust concentrations measured with this device to equivalent concentrations measured with an Isleworth 113A gravimetric dust sampler (MRE). This study demonstrated that the use of the impactor sampling head provides a viable alternative to the currently used sampling head. The results showed that comparative measurements could be linearly related for MRE dust measurements ranging from 0.5 to 5.5 mg/m3. The factor determined for converting measurements made with the new head to equivalent MRE measurements was approximately 0.5.     

EPDM橡胶海洋大气环境室内外表观老化性能的对比研究

采用光泽度、扫描电镜和傅里叶变换红外分析技术等研究了三元乙丙橡胶(EPDM)在西沙大气暴晒和室内加速老化试验条件下的表观形貌及结构的变化,探索了室内外老化表观性能的相关性.结果表明:盐雾试验条件下光泽度基本没有变化;荧光紫外试验中光泽度在开始阶段就快速下降,最后趋于平稳;在西沙大气暴晒条件下,初始阶段变化趋势并不明显,随着老化时间的增加,光泽度值下降.紫外-盐雾复合循环试验条件下光泽度变化趋势与西沙大气条件下相似,说明西沙大气暴晒试验和紫外-盐雾复合循环试验具有很好的相关性,基于光泽度分析,紫外-盐雾复合循环试验的加速倍数是25~26.红外光谱显示在西沙大气暴晒试验和紫外-盐雾复合试验中可能有β-二酮的生成,盐雾试验条件下没有β-二酮的生成.     

Toxicity of nitrogen dioxide: an introduction

Many questions, needed to advance our understanding of the mechanism of injury from high-level NO2, remain unanswered to date. This is partly due to the limited interest in the toxicity of high-level exposures, and partly due to the public pressure and interest to study the effects of low- (environmental) levels. However, the effects of exposure to high-level NO2 are of great interest to the military since high levels of NO2 may be found in combat situations. It is also important to the civilian section in occupational settings where accidents may occur as in silo filler accidents. To fill this gap in knowledge, the Department of Respiratory Research, Division of Medicine at Walter Reed Army Institute of Research took the initiative and convened a panel of experts in a symposium to discuss in depth the effects of exposure to high-level nitrogen dioxide. The symposium goals were to address the issues beginning from the chemistry of NO2 molecule, to the dosimetry of its uptake (isolated lung), to the biological effects of exposure in vivo in small animals (rats), large animals (sheep), and finally in the most relevant species, humans.     

Simultaneous sulfur dioxide and nitrogen dioxide removal by calcium hydroxide and calcium silicate solids

At conditions typical of a bag filter exposed to a coal-fired flue gas that has been adiabatically cooled with water, calcium hydroxide and calcium silicate solids were exposed to a dilute, humidified gas stream of nitrogen dioxide (NO2) and sulfur dioxide (SO2) in a packed-bed reactor. A prior study found that NO2 reacted readily with surface water of alkaline and non-alkaline solids to produce nitrate, nitrite, and nitric oxide (NO). With SO2 present in the gas stream, NO2 also reacted with S(IV), a product of SO2 removal, on the exterior of an alkaline solid. The oxidation of S(IV) to S(VI) by oxygen reduced the availability of S(IV) and lowered removal of NO2. Subsequent acidification of the sorbent by the removal of NO2 and SO2 facilitated the production of NO. However, the conversion of nitrous acid to sulfur-nitrogen compounds reduced NO production and enhanced SO2 removal. A reactor model based on empirical and semi-empirical rate expressions predicted rates of SO2 removal, NO2 removal, and NO production by calcium silicate solids. Rate expressions from the reactor model were inserted into a second program, which predicted the removal of SO2 and NOx by a continuous process, such as the collection of alkaline solids in a baghouse. The continuous process model, depending upon inlet conditions, predicted 30-40% removal for NOx and 50-90% removal for SO2. These results are relevant to dry scrubbing technology for combined SO2 and NOx removal that first oxidizes NO to NO2 by the addition of methanol into the flue duct.     

荧光猝灭法测定空气中二氧化氮和一氧化氮

NO2可被藏红T溶液吸收并转变为亚硝酸根,并且在酸性介质中,亚硝酸根可以使藏红T发生荧光猝灭,据此建立了荧光光度法测定亚硝酸根进而间接测定空气中NO2和NO的新方法。研究了硫酸,藏红T用量,柠檬酸钠用量对测定体系的影响。在最佳实验条件下,NO2-的浓度在0.023~0.276μg/mL范围内与荧光信号的降低值呈良好的线性关系,相关系数为0.9978。该方法用于测定空气中NO2和NO时的检出限分别为0.000 4 mg/m3和0.000 6 mg/m3。该方法简单、快速、检出限低,可为环境评估提供一个参考方法。     

Vertical distribution of outdoor radon and thoron in Japan using a new discriminative dosimeter

Passive measurements of outdoor radon and thoron concentrations were conducted from June 1992 to June 1993 at a monitoring station over a soil area (10 m x 6 m) in Chiba city, Japan. The measurement period was divided into 4 parts to investigate seasonal variations of radon and thoron concentrations. Ten passive radon-thoron discriminative dosimeters (R-T dosimeters) were placed in duplicate at 5 different altitudes to show the vertical distributions of outdoor radon and thoron concentrations. Outdoor radon concentrations showed no significant difference within 1.0 m above the ground, and the annual average of outdoor radon concentration was 3.85 +/- 0.19 (SE) Bq m-3. Annual averages of outdoor thoron concentrations at 0.04, 0.15, 0.25, 0.70, and 1.0 m above the ground were 40.5 +/- 4.4, 22.5 +/- 3.7, 13.9 +/- 3.1, 9.5 +/- 2.9 (SE) Bq m-3, and < 9.0 Bq m-3; the lower detection limit of the dosimeter, respectively, and their vertical profiles, n(z) (Bq m-3), were expressed well by the formula n(z) = alpha z beta. Vertical profiles of the atmospheric turbulent diffusion coefficient were also estimated from the observed thoron profiles, as expressed by the power function K(z) = AzB, of which B values were estimated to vary from 1.034 to 1.609 if averaged thoron exhalation rates during the measurement periods were within 0.3 to 2.8 (Bq m-2 s-1).     

Absorption of nitrogen dioxide and nitric oxide by soda lime

Inhaled nitric oxide (NO) is used for the treatment of pulmonary hypertension as a selective pulmonary vasodilator. However, NO is oxidized rapidly to the more toxic nitrogen dioxide (NO2). Elimination of NO2 from inspired gas is essential for safe clinical use NO. We therefore investigated the efficacy of soda lime in absorbing NO2 from NO2-containing gases. Commercially available soda limes (Soda sorb and Wako lime-A), were exposed to the following six gas mixtures containing NO and NO2 in a hypoxic carrier gas for 20 min: No. 1: NO 40 ppm; No. 2: NO 35 ppm and NO2 5 ppm; No. 3: NO 30 ppm and NO2 10 ppm; No. 4: NO 20 ppm and NO2 20 ppm; No. 5: NO 10 ppm and NO2 30 ppm; and No. 6: NO2 40 ppm. Both types of soda lime completely absorbed the NO2 in all samples when it was present (Nos 2-6). NO concentration in these gas mixtures was reduced by an amount equal to the NO2 absorbed by soda lime. NO was absorbed minimally when NO2 was not present in the mixture. Nitrite was detected from the Wako lime-A granules exposed to the test gas by the chemical analysis. These findings suggest that soda lime completely absorbs NO2 by chemical neutralization, but NO is absorbed as simultaneously absorbed NO2 only where NO and NO2 coexist. Therefore, we conclude that soda lime is useful for NO2 absorption during NO inhalation therapy but NO monitoring from a point distal to the soda lime is required for precise control of inspired NO concentration.     

Effect of nitrogen dioxide and other combustion products on asthmatic subjects in a home-like environment

Nitrogen dioxide (NO2) is one of a number of nitrogen compounds that are by-products of combustion and occur in domestic environments following the use of gas or other fuels for heating and cooking. In this study, we examined the effect of two levels of NO2 on symptoms, lung function and airway hyperresponsiveness (AHR) in asthmatic adults and children. In addition, in the same subjects, we examined the effects of the same levels of NO2 mixed with combustion by-products from a gas space heater. The subjects were nine adults, aged 19-65 yrs, and 11 children, aged 7-15 yrs, with diagnosed asthma which was severe enough to require daily medication. All subjects had demonstrable AHR to histamine. Exposures were for 1 h on five separate occasions, 1 week apart, to: 1) ambient air, drawn from outside the building; 2) 0.3 parts per million (ppm) NO2 in ambient air; 3) 0.6 ppm NO2 in ambient air; 4) ambient air+combustion by-products+NO2 to give a total of 0.3 ppm; and 5) ambient air+combustion by-products+NO2 to give a total of 0.6 ppm. Effects were measured as changes in lung function and symptoms during and 1 h after exposure, in AHR 1 h and 1 week after exposure, and in lung function and symptoms during the week following exposure. Exposure to NO2 either in ambient air or mixed with combustion by-products from a gas heater, had no significant effect on symptoms or lung function in adults or in children. There was a small, but statistically significant, increase in AHR after exposure to 0.6 ppm NO2 in ambient air. However, there was no effect of 0.6 ppm NO2 on AHR when the combustion by-products were included in the test atmosphere nor of 0.3 ppm NO2 under either exposure condition. We conclude that a 1 h exposure to 0.3 or 0.6 ppm NO2 has no clinically important effect on the airways of asthmatic adults or children, but that 0.6 ppm may cause a slight increase in airway hyperresponsiveness.     

Measurements of colour constancy by using a forced-choice matching technique

In order to compare the reactivity of glutamic acid decarboxylase (GAD) antibodies recognizing linear and conformational epitopes as islet cell cytoplasmic antibodies (ICA), monoclonal antibodies were generated. An ELISA displacement test using two biotinylated monoclonals recognizing a linear (M61/7E11) or a conformational GAD65 epitope (M65/6B12) was performed to identify epitope regions recognized by monoclonal GAD antibodies. The GAD binding by monoclonal GAD antibodies was tested by immunofluorescence on fixed and unfixed pancreatic sections of human, rat, and mouse, and by Dot-blot experiments. 16/23 (69.6%) of the monoclonals were specifically reactive with GAD65 and 7/23 (30.4%) were reactive with both GAD isoforms. 8/16 (50%) of monoclonal GAD65 antibodies recognized a linear GAD epitope located at the N-terminus (pattern 1). 5/16 (31.3%) displaced M65/6B12, indicating the recognition of a conformational GAD epitope (pattern 2). Monoclonals belonging to patterns 1 and 2 showed strong ICA binding. 3/16 (18.8%) of monoclonals specific for GAD65 with weak or no immunostaining of pancreatic islets (pattern 3) did not inhibit the binding of both biotinylated antibodies in the displacement test, indicating other epitope specificities. In conclusion, GAD antibodies recognizing both conformational and linear epitopes of the GAD65 molecule are involved in ICA binding with strong reactivity. Furthermore, results obtained with monoclonals of pattern 3 suggest the occurrence of GAD65 epitopes partly inaccessible on cryosections, which may result in an ICA-negative test of GAD65 autoantibody positive sera.     

Measurements of differential scattering cross section using a ring transducer

A procedure for the measurement of intrinsic scattering object properties is presented and used to obtain illustrative results. The procedure is based on the measurement of the scattered acoustic field as a function of scattering angle and frequency. Measurements are normalized using analytically determined expressions for emitter and detector beams resulting from a combination of unfocused linear elements arranged in a circular configuration. The spatial effects of finite emitter pulse length and detector gate length are represented by a convolution formula valid for narrow-band transmitted signals and long receiver gates. The normalization includes correction for target absorption as well as measurement of the directly transmitted acoustic power in the free field and yields the average differential scattering cross section per unit volume. Under the Born approximation, this quantity is directly proportional to the spatial-frequency spectrum of the scattering medium inhomogeneities. Measured results are reported for two phantoms consisting of glass microspheres embedded in a weakly absorbing agar background medium. For the phantoms employed, scattering effects, rather than increased absorption, are shown to account for most of the difference in transmission loss between pure agar and agar with glass spheres. The measured differential scattering cross sections are compared with theoretical cross sections for distributions of glass spheres measured experimentally. The measured values show good relative agreement with theory for varying angle, frequency, and phantom properties. The results are interpreted in terms of wave space resolution and the potential for tissue characterization using similar fixed transducer configurations.