Abstract  Simultaneous temporally resolved indoor and outdoor measurements of ammonia and nitric acid are valuable for determining the gas-particle equilibrium conditions governing concentrations of ammonium nitrate aerosol. We report the results of simultaneous automated indoor and outdoor measurements of ammonia and nitric acid concentrations made at an unoccupied, single-story residence in Clovis, CA during three periods from October 2000 to January 2001. The measurements were conducted as part of a controlled study to explore mechanisms governing indoor concentrations of fine aerosols of outdoor origin. The gas-phase measurements were performed using diffusion denuders and ion chromatography with 30 min temporal resolution and detection limits below 1 ppb. The conditions of the field experiment span a wide range of outdoor climate as well as natural and forced indoor conditions. During all periods ammonia concentrations were generally slightly higher indoors than out, with both outdoor and indoor concentrations varying in a range from approximately 5 to 30 ppb. Nitric acid was only detected in outdoor air in October 2000, at concentrations up to 3 ppb. During the October period, the product of outdoor nitric acid and ammonia concentrations sometimes deviated from that expected for equilibrium between gas and ammonium nitrate particulate phases and the degree and direction of disequilibrium were correlated with trends in air temperature. The consistently low indoor concentrations of nitric acid were not consistent with equilibrium between gas and particle phases and suggest that a combination of low penetration into the building and a high loss rate for nitric acid reduce indoor concentrations significantly below those outdoors.

Abstract  The highest O3 levels observed during the 1995 Southern Oxidants Study in middle Tennessee occurred during a period of air stagnation from July 11 through July 15. Extensive airborne (two fixed wing and one helicopter) and ground-based measurements of the chemistry and meteorology of this episode near Nashville, Tennessee, are presented. In situ airborne measurements include O3, NO sub(y), NO, NO2, SO2, CO, nitrate, hydrocarbons, and aldehydes. Airborne LIDAR O3 measurements are also utilized to map the vertical and horizontal extent of the urban plume. The use of multiple instrumented research aircraft permitted highly detailed mapping of the plume chemistry in the vertical and horizontal dimensions. Interactions between the urban Nashville plume (primarily a NOx and hydrocarbon source) and the Gallatin coal-fired power plant plume (primarily a NOx and SO2 source) are also documented, and comparisons of ozone formation in the isolated and mixed urban and power plant plume are presented. The data suggest that during this episode the background air and the edges of the urban plume are NOx sensitive and the core of the urban plume is hydrocarbon sensitive. Under these worst case meteorological conditions, ambient O3 levels well over the level of the new National Ambient Air Quality Standard (NAAQS) for ozone (80 ppb) were observed over and just downwind of Nashville. For example, on July 12, the boundary layer air upwind of Nashville showed 60 to 70 ppb O3, while just downwind of the city the urban plume maximum was over 140 ppb O3 . With a revised ozone standard set at 80 ppb (8 hour average) and upwind levels already within 10 or 20 ppb of the standard, only a slight increase in ozone from the urban area will cause difficulty in attaining the standard at monitors near the core of the urban plume during this type of episode. The helicopter mapping and LIDAR aircraft data clearly illustrate that high O3 levels can occur during stagnation episodes within a few kilometers of and even within the urban area. The extremely light boundary layer winds (1-3 m s(-1) ) contributed to the creation of an ozone dome or blob which stayed very near to the city rather than an elongated plume. The small spatial scale of the zone of high O3 concentrations is mapped in detail demonstrating that the regulatory monitoring network failed to document the maximum O3 concentrations. Modelers using such regulatory data to test photochemical algorithms need to bear in mind that magnitude and frequency of urban ozone may be underestimated by monitoring networks, especially in medium-sized urban areas under slow transport conditions. Finally, this effort shows the value of collaborative field measurements from multiple platforms in developing a more complete picture of the chemistry and transport of photochemical O3.

Abstract  In lead nitrate treated animals the basal adrenal corticosterone levels were significantly increased alongwith the lowering of adrenal ascorbic acid. The basal plasma corticosterone levels did not change significantly in these rats. Following exposure to immobilization stress, the adrenal corticosterone levels were more markedly enhanced in lead nitrate treated rats than normal stressed animals. On the other hand, plasma corticosterone response to stress was found to be less pronounced in treated rats in comparison to normal stressed rats. The adrenal ascorbic acid contents significantly decreased in both control and treated rats following exposure to stress. These observations suggest that adrenocortical response to stress is considerably altered in lead nitrate treated animals.

Abstract  In the present study we have examined the effect of a single dose of the mitogen lead nitrate (75 mumols/kg body wt) on the methylation status of hepatic DNA in male Wistar rats. It was found that extensive hypomethylation of hepatic DNA occurs in mitogen-treated rat liver. This effect could be seen as early as 12 h after metal treatment and parallels the changes in liver weight. Probing with the methylation-sensitive enzymes HpaII, MspI, and HaeIII confirmed HPLC analyses and showed that methylation at these sites was affected by lead treatment. DNA hypomethylation has already been found in regenerating rat liver and in hepatic (pre)malignant lesions when compared to normal nondividing liver. Thus the lowering of the DNA 5-methylcytosine content appears to be a property characteristic of cellular proliferation, regardless of whether it is caused by partial hepatectomy, carcinogen treatments, or mitogen administration.

Abstract  The Atlantic Rain Forest of the Serra do Mar close to Cubatao, Sao Paulo State, SE Brazil, is severely affected by the emissions of a big industrial complex. Measurements of trace substance concentrations in air as well as in rain were carried out over a period of 6 years to investigate the interrelation of pollution and vegetation damage. Due to the local atmospheric circulation, orographic clouds occur very frequently at the top of the Serra do Mar, where vegetation damage also is very high. Therefore, additional information was required about trace substance deposition via cloud water. During three field experiments, various samples of cloud water and of the interstitial aerosol were taken by help of a sampling device especially modified for this purpose, and were analysed for the major anions and cations (hydrogen ions, ammonium, chloride, sodium, nitrate and sulphate). The trace substance concentrations found in cloud water were in the same range as for polluted sites in Europe. Over all samples, about 90-100% of the trace substances-both gaseous and particulate matter-found in the atmosphere before a cloud event were found in the cloud water. A resistance model using meteorological input data (wind speed, atmospheric liquid water content) was adapted to the characteristics of the Atlantic Rain Forest to estimate the cloud water deposition to vegetation. The results from cloud water analyses and from modelled cloud water deposition were combined to investigate the ion deposition to the vegetation. A rough estimate of the annual deposition showed, that the deposition via rain is in the order of one magnitude (factor 6-40) higher than that via cloud. The high amount of water deposition via precipitation overcompensates the higher trace substance concentrations in cloud water. Furthermore the trace substance deposition to vegetation via cloud water in the Atlantic Rain Forest is in the order of one magnitude lower than for typical German spruce forests due to the higher capture efficiency of the needles compared to that one of the leaves in the Serra do Mar. (C) 2003 Elsevier Science Ltd. All rights reserved.

Abstract  In the human environment, nitrosatable amine precursors to N-nitroso compounds and nitrosating species such as nitrite and oxides of nitrogen are abundant. As a result, the formation of N-nitroso compounds and human exposure to these compounds show a rather complex pattern. The largest known human exposures to exogenous N-nitrosamines occur in the work place. This is particularly evident in the rubber and tyre manufacturing industry and in metal cutting and grinding shops. Nearly all industries which are concerned with the production and/or use of amines have a related nitrosamine problem. Outside the industrial environment, commodities such as cosmetics, pharmaceuticals, rubber and household products, which are either prepared from amines or contain high concentrations of amino compounds, may be subject to contamination by low concentrations of N-nitroso compounds. This contamination may result from the use of contaminated starting materials, in particular amines, or from the formation of N-nitroso compounds during manufacturing processes. A similar problem exists with agricultural chemicals. As our knowledge of the occurrence and formation of N-nitroso compounds in the environment increases, preventive measures can be introduced, particularly in manufacturing industries, to reduce the levels of human exposure to nitrosamines in the work place and to protect the consumer from nitrosamine exposure from household commodities.

Abstract  This study develops a theory for the Gaussian plume equation to account for the formation of secondary sulfate aerosol and nitrate aerosol from the oxidations of gaseous SO2 and NO, emissions. In addition, the mechanisms of scavenging, dry deposition, background pollutant transport and subsidence from the top planetary boundary layer are also considered. A Gaussian trajectory transfer-coefficient model (GT,) has been developed. Wind vector, stability class and mixing height among each time interval along a trajectory are allowed to change. Quantification on the source/ receptor relationship of primary pollutants and the secondary aerosols from sources can be determined in a single model run. Nonetheless, it should be noted that the current formulation depends on the explicit description of the oxidation rates of gaseous SO2 and NOx. Since reactive chemistry, in general, is nonlinear, this would be the limitation of the approach. Alternatively, prior to application of the model to a site, the rates calibrated to specific time and the location of interest are suggested. (C) 2003 Elsevier Ltd. All rights reserved.

Abstract  The main aim of the study was to determine the role of calcium in the amelioration of lead toxic effects in plants with accordingly high/low level of Pb-tolerance and high/low Ca-deficiency tolerance. The study was performed on maize, rye, tomato and mustard. Plants were cultivated in modified Knop's solution. They were subjected to Ca-deficiency, and to lead nitrate administered in the presence of four calcium nitrate concentrations 3.0, 2.4, 1.2, 0.3 mM. Lead-tolerance and tolerance to Ca-deficiency were determined, as were concentration of the studied elements in plant tissues, and the Pb deposition pattern at the ultrastructural level (electron microscopy study, X-ray microanalysis). In all studied plants, lead toxicity increased as medium calcium content decreased, however, only in the Ca-deficiency sensitive mustard with low Pb-tolerance was it accompanied by a rise in tissue lead concentration. In contrast, lead root and shoot levels did not increase in the highly Ca-deficiency tolerant tomato, mustard and rye with high Pb-tolerance irrespective of the Ca2+ regimens applied. Thus, in these plants, lead's unfavourable effects resulted only from the higher toxicity of the same amount of lead in tissues at low calcium in the medium. Of particular relevance is the finding by electron microscopy and X-ray microanalysis, that under low calcium in both highly Ca-deficiency tolerant and Ca-deficiency sensitive plants, less efficient Pb2+ detoxification was accompanied by the restriction of the formation of large lead deposits in cell walls. Obtained results are novel in demonstrating calcium involvement in the lead deposition in the cell wall, thus in the regulation of the internal lead detoxification.

Abstract  The effects of sublethal concentrations of lead nitrate on the growth and reproduction of the African composting earthworm species, Eudrilus eugeniae, was studied by exposing worms in an organic substrate to lead-nitrate-contaminated food over a period of 76 days. The results revealed that growth was initially affected negatively by the presence of lead, while the maturation rate and cocoon production were not affected. In agreement with other studies on Eisenia fetida, cocoon viability was affected negatively by lead, making this a sensitive toxicity endpoint.

Abstract  Nine-week-old zinc-sufficient (100 mg zinc/kg feed) and zinc-deficient (7 mg zinc/kg feed) noninbred male Sprague-Dawley rats were given free access 5 days a week to deionized drinking water containing low (0.05%) or high (0.25%) quantities of benzylmethylamine (BMA) and concurrently 0.5% NaNO2. In contrast to the action of the preformed carcinogen N-nitroso-N-benzylmethylamine, which almost invariably produced esophageal tumors, oral administration of its precursors, BMA and NaNO2, resulted in forestomach tumors as well. In both the high- and low-BMA groups given precursors for 16 weeks, the incidence of papillomas in both the esophagus and forestomach was significantly higher in the zinc-deficient than in the zinc-sufficient rats, but zinc deficiency did not significantly increase the yield of forestomach carcinomas. However, when combined high BMA and NaNO2 administration was prolonged to 37 weeks, the yield of forestomach carcinomas was significantly greater in the zinc-deficient than in the zinc-sufficient animals. Because endogenous synthesis of N-nitrosamines from ingested precursors is an important source of human exposure to these carcinogenic compounds and because dietary zinc deficiency might be operating in some areas with a high incidence of esophageal cancer, our data are of more than routine significance.

Abstract  The application of newly developed semi-continuous aerosol monitors allows for the measurement of all the major species Of PM2.5 on a 1-h time basis. Temporal resolution of both non-volatile and semi-volatile species is possible. A suite of instruments to measure the major chemical species of PM2.5 allows for semi-continuous mass closure. A newly developed dual-oven Sunset carbon monitor is used to measure non-volatile organic carbon, semi-volatile organic carbon and elemental carbon. Inorganic species, including sulfate and nitrate, can be measured with an ion chromatograph based sampler. Comparison of the sum of the major chemical species in an urban aerosol with mass measured by an FDMS resulted in excellent agreement. Linear regression analysis resulted in a zero-intercept slope of 0.98 +/- 0.01 with an R-2 = 0.86. One-hour temporal resolution of the major species Of PM2.5 may reduce the uncertainty in receptor based source apportionment modeling, will allow for better forecasting Of PM2.5 episodes, and may lead to increased understanding of related health effects. (c) 2007 Elsevier Ltd. All rights reserved.

Abstract  The concentration time series of chemical species measured in PM2.5 samples from four speciation trend network (STN) sites in the New York City metropolitan area and a upwind background site were explored. PM2.5 concentrations and chemical compositions measured in metropolitan area of New York City are uniform. About 69-82% Of PM2.5 mass derives from transport. The most important constituents of the PM2.5 were SO42-, NH4 and NO3- and account 54-67% of PM2.5 mass. More than 93% of SO42- and about 54-65% of NO3- are likely to have been transported into the NYC area based on the concentrations observed at the background site. Backward air parcel trajectories indicate that coal-fired power plants in the border area among West Virginia, Ohio and Pennsylvania are related to typical high PM2.5 events having peak secondary pollutant concentrations in New York City. Positive matrix factorization (PMF) was applied to identify the PM2.5 sources and estimate the source contributions. Sources common to all five sites included secondary sulfate, secondary nitrate, soil and aged sea salt. Oil combustion was identified at four of the sites. At the Elizabeth site, the oil combustion source appears to show an influence from ship emissions. Motor vehicles were apportioned into two sources (gasoline and diesel) at three site and three sources at the Elizabeth site, probably because of its proximity to a major interstate highway. At the Queens College site, only a combined motor vehicle factor could be resolved. The source profiles, source contributions and seasonal or weekday variations derived by PMF are compared to source inventories for the area. It appears that there were more vehicle exhausts and less dust and wood smoke than are indicated by the source inventories. (c) 2006 Elsevier Ltd. All rights reserved.

Abstract  Size-fractionated particulate matter (PM) samples were collected from six U.S. cities and chemically analyzed as part of the Multiple Air Pollutant Study. Particles were administered to cultured lung cells and the production of three different proinflammatory markers was measured to explore the association between the health effect markers and PM. Ultrafine, fine, and coarse PM samples were collected between December 2003 and May 2004 over a 4-wk period in each city. Filters were pooled for each city and the PM samples were extracted then analyzed for trace metals, ions, and elemental carbon. Particle extracts were applied to cultured human primary airway epithelial cells, and the secreted levels of interleukin-8 (IL-8), heme oxygenase-1, and cyclooxygenase-2 were measured 1 and 24 h following exposure. Fine PM sources were quantified by the chemical mass balance (CMB) model. The relationship between toxicological measures, PM sources, and individual species were evaluated using linear regression. Ultrafine and fine PM mass were associated with increases in IL-8 (r2 = .80 for ultrafine and r2 =.52 for fine). Sources of fine PM and their relative contributions varied across the sampling sites and a strong linear association was observed between IL-8 and secondary sulfate from coal combustion (r2 =.79). Ultrafine vanadium, lead, copper, and sulfate were also associated with increases in IL-8. Increases in inflammatory markers were not observed for coarse PM mass and source markers. These findings suggest that certain PM size fractions and sources are associated with markers of lung injury or inflammation.

Abstract  . This study investigates effects of nitrogen and phosphorus on high Arctic heath vegetation, particularly bryophytes.

. Heath communities received factorial combinations of nitrogen (0, 10 and 50 kg ha(-1) yr(-1)) and phosphorus (0 and 5 kg ha(-1) yr(-1)) in five applications per growing season, for 8 yr.

. Nitrogen decreased lichen cover but did not affect cover of any other functional type. However, just 10 kg ha(-1) yr(-1) increased the proportion of physiologically active bryophte shoots, and decreased their nitrate assimilation capacity. Phosphorus had greater effects, and the combination of both nutrients altered species composition. Individual bryophyte species displayed contrasting responses to fertilization, suggesting that they should not be grouped as a single functional type.

. The 'critical load' of nitrogen for Arctic heath lies below 10 kg hal yr-l. Nitrogen and phosphorus are colimiting in this sytem, so the critical load of nitrogen will be lower where phosphorus availability is greater. Responses of vegetation to any increase in net mineralisation due to soil warming will depend on the ratio in which nitrogen and phosphorus availabilities increase. The effects of nutrient enhancement are very persistent.

Abstract  The biogeochemistry of nitrogen (N) was evaluated for three forest ecosystems [Woods Lake (WL), Pancake-Hall Creek (PHC) and Huntington Forest (HF)] in the Adirondack region of New York, U.S.A. to evaluate the response of a range of N atmospheric inputs and experimental N additions. Bulk N deposition was higher at sites in the west than those in the central and eastern Adirondacks. These higher atmospheric N inputs were reflected in higher bulk throughfall fluxes of N (WL and PHC, 10.1 and 12.0 kg N ha(-1) yr(-1), respectively) in the western Adirondacks than at HF (4.6 kg N ha(-1) yr(-1)) in the central Adirondacks. Nitrogen was added to plots as (NH4)(2)SO4 at 14 and 28 kg N ha(-1) yr(-1) or as HNO3 at 14 kg N ha(-1) yr(-1). Litter decomposition rates of Fagus grandifolia and Acer rubrum were substantially higher at WL and PHC compared to HF but were not affected by experimental N additions. Results using mineral soil bags showed no effects of N addition on N and C concentrations in soil organic matter, but C and N concentration increases were less at WL and PHC compared to HF. Soil solution nitrate (NO3-) concentrations at 15-cm depth in the reference plots were higher at PHC than at WL and HF while at 50-cm concentrations were higher at PHC and WL than at HF. The reference plots at the two sites (WL and PHC) with the highest atmospheric inputs of N exhibited lower N retention (53 and 33%, respectively) than HF (68%) in reference plots. The greatest increase in NO3- loss in response to the experimental treatments occurred at HF where the HNO3 additions resulted in the highest NO3- concentrations and lowest N retentions. In contrast, at WL and PHC increases in soil water NO3- were not evident in response to experimental N additions. The results suggest that the two sites (WL and PHC) in the western Adirondacks did not respond to additional N inputs although they have experienced elevated atmospheric N inputs and higher N drainage losses in reference plots than the HF site in the central Adirondacks. Some of these differences in site response may have also been a function of stand age of WL and PHC that were younger (24 and 33 years, respectively) than the HF (age similar to 70). Highest NO3- fluxes in the reference plots across the sites corresponded to higher delta N-15 values in soil and plants. An experimental addition experiment at PHC found that the forest floor and the mineral soil were the largest sinks for experimentally added N.

Abstract  The Great Smoky Mountains in the southeastern U.S. receive high total atmospheric deposition of sulphur and nitrogen (N) and contain large areas of shallow, poorly buffered soils. Results from extensive surveys conducted in October 1993 and March 1994 showed that stream pH values were near or below 5.5 and Acid Neutralizing Capacity (ANC) was below 50 Áeq░L-1 at high elevations. Mechanisms of acidification vanes among stream systems in the study. We classified each study catchment into one of five water quality districts based upon within-basin elevational gradients of streamwater quality. Geologic factors, cl: the presence of calcareous or pyritic bedrock types exhibited a major influence on water quality and within-basin elevational gradients. Atmospheric deposition is an important factor affecting water quality at high elevations in all districts. Nitrate was the dominant strong acid anion in streamwater in many catchments, particularly at high elevation and especially in basins draining old growth forests. Most high elevation catchments appear to he N saturated. Continued high atmospheric loadings of N will likely spread N saturation of catchments downslope into areas where second growth forests are now maturing. Stream sulphate concentrations were lower than expected at higher elevations and may be related to the N saturation status of these systems.

Abstract  High-elevation red spruce-Fraser fir forests in the Southern Appalachian mountains: 1) receive among the highest rates of atmospheric deposition measured in North America, 2) contain old-growth forests, 3) have shown declines in forest health, 4) have sustained high insect-caused fir mortality, and 5) contain poorly buffered soils and stream systems. High rates of nitrogen and sulphur deposition (~1900 and ~2200 Eqòha-1òyr-1 , respectively) are dominated by dry and cloud deposition processes. Large leaching fluxes of nitrate-nitrogen (100-1400 Eqòha-1òyr-1) occur within the sail profile. We have expanded the study to the watershed scale with monitoring of: precipitation, throughfall, stream hydrology, and stream chemistry. Two streamlets drain the 17.4 ha Noland Divide Watershed (1676-1920m) located in the Great Smoky Mountains National Park A network of 50 20x20 m plots is being used to assess stand structure, biomass, and soil nutrient pools. Nitrate is the predominant anion in the streamlets (weighted concentrations: 47 and 54ÁeqòL-1 NO3-; 31 and 43 ÁeqòL-1 SO4-2). Watershed nitrate export is extremely high (~1000 Eqòha-1yr-1), facilitating significant base cation exports. Stream acid neutralizing capacity values are extremely low (-10 to 20 ÁeqòL-1) and episodic acidifications (pH declines of a full unit in days or weeks time) occur. Annual streamwater sulfate export is on the order of 770 Eqòha-1òyr-1 or about one-third of total annual inputs, indicating there is net watershed sulfate retention. The system is highly nitrogen saturated (Stage 2, Stoddard, 1994) and this condition promotes both chronic and episodic stream acidification.

Abstract  A photochemical box model (NITE-UP) supplied with an updated and additional daytime and nighttime chemical scheme, has been applied to nighttime emissions from a major city (London). Studies have been made of the importance of the temperature-dependent rate constant of the homogeneous and heterogeneous reaction

N2O5 + H2O --> 2HNO(3)

on NO3 radicals production. The involvement of the nitrate radical in the nighttime tropospheric chemistry and its influences on the concentrations of other species including N2O5, HNO3, OH, HO2, as well as on the subsequent ozone formation have been modelled for the area downwind of London, under summertime and springtime conditions. The significance of the representation of the NO3 chemistry in computational photochemical models is discussed. (C) 1997 Elsevier Science Ltd.

Abstract  The first aerial observations of atmospheric pollutants over mainland China were performed as an international collaborative research effort in March, 2002. Observation flights over Bo Hai were made from Dalian to Dandong, Jinzhou, and Qingdao. High concentrations of gaseous pollutants (O-3, SO2, and NOx) were observed; SO2 and NOx showed a very good correlation. Comparing the chemical compositions of particulate pollutants showed that there was a high concentration of sulfate ions in fine particles. Concentrations of sulfate and nitrate ions showed good correlations with concentrations of both ammonium and calcium ions, suggesting that the aerosols over the Bo Hai area were well neutralized. (c) 2005 Elsevier Ltd. All rights reserved.

Abstract  This paper reviews the data concerning the atmospheric occurrence of nitrophenols, both in the gas and in the condensed phase (rainwater, cloud, fog and snow). Data obtained from field campaigns are reported, together with a description of the analytical techniques employed for the identification and quantification of nitrophenols. Analysis is usually performed using techniques such as High Performance Liquid Chromatography (HPLC) or Gas Chromatography-Mass Spectrometry (GC-MS), with the sampling method largely determined according to the matrix under investigation. The sources of atmospheric nitrophenols include direct emissions resulting from combustion processes, hydrolysis of pesticides (e.g. parathion) and the secondary formation of nitrophenols in the atmosphere. Atmospheric nitration of phenol can take place both in the gas and liquid phases, but the relative importance of these processes is still under discussion. The gas-phase nitration involves reaction between phenol and *OH+ *NO2 during the day or *NO3 + *NO2 during the night. Gas-phase nitration during the day yields only 2-nitrophenol (2-NP); while during the night it is thought that both 2-NP and 4-nitrophenol (4-NP) may be formed. Because of many gaps in the experimental evidence it is apparent that more research is required to indicate whether the 4-NP present in the environment can be accounted for by this nighttime process. Nitration in the condensed phase can be initiated by electrophilic nitration agents such as N2O5 and CINO2. Other liquid-phase processes can also take place, in the presence of *NO3, nitrate and nitrite, in the dark and under irradiation. Condensed-phase processes have been shown to yield 2-and 4-NP in similar amounts. It is also important to consider the atmospheric sinks of nitrophenols. The rate constant for the reaction between 2-NP and *OH in the gas phase is rather low (9.0 X 10(-13) cm(3) molecule(-1) s(-1)), while incomplete data are available for the reaction with *NO3. In addition, condensed-phase processes might also represent an important nitrophenol sink. Potential loss routes include the reaction with radicals such as *OH and *NO3 in aqueous solution as well as the nitration to form the dinitrophenols. (C) 2004 Elsevier Ltd. All rights reserved.

Abstract  Carbon monoxide causes a perivascular oxidative injury in animals, and we tested the hypothesis that endothelial cells could be a source of the injurious oxidants. Studies were undertaken to assess whether exposure to carbon monoxide would cause cultured bovine pulmonary artery endothelial cells to liberate reactive species. Concentrations of carbon monoxide between 11 and 110 nM caused progressively higher concentrations of nitric oxide to be released by endothelial cells based on measurements of nitrite and nitrate. Intracellular production of peroxynitrite was indicated by elevated concentrations of nitrotyrosine, and extracellular liberation of peroxynitrite was indicated by oxidation of p-hydroxyphenylacetic acid and dihydrorhodamine-123. Carbon monoxide did not disturb mitochondrial function based on the rate of oxygen consumption, intracellular production of hydrogen peroxide, and the ability of cells to reduce 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Carbon monoxide also did not alter arginine transport by cells or nitric oxide synthase activity, but it was found to increase steady state levels of nitric oxide by competing for intracellular binding sites. Acute cytotoxicity from carbon monoxide, assessed as radioactive chromium leakage, was due to nitric oxide-derived oxidants. A delayed cell death, whose mechanism is not entirely clear, was also demonstrated by chromium leakage and uptake of vital stain. These findings offer a possible mechanism for adverse health effects caused by carbon monoxide at concentrations ranging from the relatively low levels in polluted environments to levels typically encountered with life-threatening poisoning. Carbon monoxide causes oxidative stress by a novel mechanism involving a competition for intracellular binding sites which increases steady state levels of nitric oxide and allows for generation of peroxynitrite by endothelium.

Abstract  U.K. Department of Environment Air Quality Research Program.